# Non PWM controller discussion



## ga2500ev (Apr 20, 2008)

I wanted to restart the discussion on non PWM controllers. PWM controllers have been discussed to death here. However, because they stress all their electronics at full pack voltage at all times, the construction of one DIY seems to be a significant challenge.

Non PWM controllers, including contactor controllers, rectactor, controllers, and the BatPack controller seem to offer some advantages over PWM controllers:

1) They have higher efficiency due to less switching losses.

2) They function in limp mode even if part of the controller fails. This gives a higher measure of reliability.

3) Subcomponents have less stress, so can be lower voltage and offer higher efficiency. Plus they are cheaper.


So I wanted to talk about there types of controllers and ask a few questions. My goal is to design a controller that can function from 96-144V.

The Contactor/Rectactor

The basic design was offered by Lee Hart in an EVDL post. The basic two battery design looks the image loaded below.

This is a serial/parallel controller. First S1A/S1B are turned on together to connect the batteries in parallel. Then S2 bypasses the current limiting resistor which bumps the speed. Finally the S1 switches are turned off and S3 turned on which connects the batteries in series, doubling the voltage to the motor.

The S1 switches, when replaced with diodes becomes a rectactor. At low speeds there is a diode drop of voltage across each battery. As the S3 switch switches in, the diodes are bypassed providing full power to the power. Also there is a need for a main contactor because with the diodes the minimum voltage is always routed to the motor.

A more modern idea is the BatPack. You can find it here:

http://www.redrok.com/ev.htm

I've talked about it in the past. The idea is to connect BatPack modules (shown below) serially. Each module can be a different voltage (unlike the contactor/rectactor (CR) designs). The controller powers a subset of the modules, by switching on the SP switch, to power the vehicle, while others are bypassed, using the SB switch. As with the rectactor, the SB switch can be substituted with a diode and its corresponding diode drop.

Now the BatPack, unlike the CR designs, drains the batteries in the subpack asymmetrically. In a CR design, all the batteries are used at every step. But with the BatPack, are dropped out which means that no power is being drawn. The BP uses battery management to monitor the voltage of each pack and to switch in stronger packs while dropping out weaker packs for a particular voltage. So for example if we have a BatPack with 2 12V modules and 2 24V modules and the driver is calling for 36V, then the controller would select the strongest 12V pack and the strongest 24V pack and turn them on. As long as they are the strongest voltage packs they remain selected for that voltage. But if their voltage drops below the corresponding unused pack, then that pack is switched in.

Now to my questions. I'm really interested in the BatPack. The design makes sense. My first question is that if the SP switch is implemented with MOSFETS then where can you draw the gate voltage required to turn on the MOSFETs? You need the gate voltage to be above the source, which is connected to the positive terminal for the battery in the module. I presume that a charge pump would need to be implemented to generate the gate voltage?

The second question is about the bypass switch. While using a diode is an easy solution, the added diode drops will burn off quite a bit of energy as heat. What would happen if you replaced that switch with MOSFETs? Would those MOSFETS have to support the voltage of the entire pack? Or just the voltage of the battery that is bypassed? Or is it related to the voltages above/below that switch?

Any thoughts welcome.

ga2500ev


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## Qer (May 7, 2008)

I have a serious problem combining these two statements describing the same construction:



ga2500ev said:


> 1) They have higher efficiency due to less switching losses.





ga2500ev said:


> Then S2 bypasses the current limiting resistor which bumps the speed.


Switching losses are usually just a few percent (maybe as low as 1-2% depending on the construction), current limiting resistors usually introduce losses of tens of percents. If you introduce any kind of resistance (no matter if it's in the form of resistors, excessive cabling, resistance in the contactors) your efficiency will drop like a stone in vacuum. On Saturn.

I also doubt this part:



ga2500ev said:


> 2) They function in limp mode even if part of the controller fails. This gives a higher measure of reliability.


I worked a while for the Swedish telephone company (back in the days where there were ONE telephone company owned by the government) and one of my tasks were doing maintenance on the relays (this was back in the days where most telephone stations still used relays rather than computers) because relays, or contactors, need maintenance if they're heavily used. The contactor in an ordinary EV doesn't switch very often during a year when it's only activated once per trip but if you have a bank of contactors that regulates throttle they will probably need regular maintenance. So I think that you will find out that the reliability actually will be lower, at least compared to a good silicon based controller like the Zilla.

But it will definitely make a very interesting sound, much like the trams I rode when I was a kid. They clattered a LOT when the driver changed acceleration where modern trams are pretty boring since they're almost silent. 

Just make sure you're adding enough fuses to avoid an accident if, for example, a contactor hangs (it does happen, especially when they start to get worn down). Shorting a battery pack, or parts of a battery pack, is not something you want to risk...


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## ga2500ev (Apr 20, 2008)

Qer said:


> I have a serious problem combining these two statements describing the same construction:
> 
> 
> 
> ...


That resistor is in place to limit the initial torque at low voltage so the vehicle doesn't shoot off like it's been loaded in a cannon. it's only for the first few seconds from a standing start.

OTOH at 16 KHz there are 2 switch transistions every 62.5 uS. Even if the switch time is only 1 uS per switch then that's a 3.2% loss all the time.

Also if you implement with semiconductor switches, then you can PWM those switches to limit the torque initially then have them switch permanently once the vehicle is moving.



> I also doubt this part:
> 
> 
> 
> ...


Qer, I think you missed my point. At the end I was asking how can you implement the structure of these types of controllers using semiconductor switches? So you use MOSFETS instead of actual contactors.

It's the structure of the controller that I want to keep, not the actual parts. I don't want to use actual contactors because frankly they cost too much, are too noisy, and as you pointed out, require maintenance.

Any controller structure is going to require switches. The question is how do you organize them and how fast do you switch them?

Go back to the rectactor. Imagine that S2 and S3 are MOSFETS and S1 diodes. So there are no contactors. Now since S2 (which fundamentally is the PWM switch in a PWM controller) is a semiconductor switch, it can be PWMed at low speeds then locked in once the vehicle has gotten up to speed.

Same with the BatPack modules. They are already switched at 100 Hz. Turn on one 12V pack at half power and you have a 6V source to the motor.

I certainly do not want actual contactors. However, I am very interested in figuring out how to replace those contactors and diodes with MOSFET switches.



> But it will definitely make a very interesting sound, much like the trams I rode when I was a kid. They clattered a LOT when the driver changed acceleration where modern trams are pretty boring since they're almost silent.
> 
> Just make sure you're adding enough fuses to avoid an accident if, for example, a contactor hangs (it does happen, especially when they start to get worn down). Shorting a battery pack, or parts of a battery pack, is not something you want to risk...



Again I'm interested in the structure, not the components.

ga2500ev


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## Qer (May 7, 2008)

ga2500ev said:


> OTOH at 16 KHz there are 2 switch transistions every 62.5 uS. Even if the switch time is only 1 uS per switch then that's a 3.2% loss all the time.


Well, if you're using MOSFET's as you suggest further down there will be a lot of Ron's in the chain which will result in rather substantial losses as well. I'm not convinced it's an improvement. Also, I believe our numbers for our prototype is better than 3.2% losses, but I'll leave that to Tesseract to sort out if he likes.



ga2500ev said:


> Also if you implement with semiconductor switches, then you can PWM those switches to limit the torque initially then have them switch permanently once the vehicle is moving.


But then you will have to implement both a PWM-controller and a PWM-free controller, ending up with twice the problems...



ga2500ev said:


> Qer, I think you missed my point. At the end I was asking how can you implement the structure of these types of controllers using semiconductor switches? So you use MOSFETS instead of actual contactors.


Well, it's doable but considering the amount of contactors/MOSFETs/whatever you'll need, it's not going to be cheap. The simplest approach is probably to use solid state relays but they don't come cheap. Especially not if they need to handle DC. How many steps do you want the controller to handle? If it's enough with 3 power steps (1/4, 1/2 and full pack voltage) you still need 9 switches that each can handle max current.

Looking at Digikey the strongest solid state relay for DC I can find handles max 100 Ampere and 60 Volt (which, to say the least, is a bit on the low side) and they cost $120. Each. They have a MOSFET that can handle 200 Volt 580 Ampere and it "only" cost $145, but you still need at least 9 of them. You can probably find much cheaper on E-bay, but in case you want a little more than three speeds the amount of MOSFET's will increase drastically and thus also the cost.

Then there's another problem involved, if you use silicon you need to limit the current and make damn sure you don't exceed the rating. If you do it by starting to PWM when things go rough you will enter that twilight zone where spikes and heat dissipation blow things up for you and if you do it by switching down to a lower voltage you will never be able to get maximum current out of your pack and the performance will suffer.

But it's definitely doable, just not very practical. However, to answer some of your questions:



ga2500ev said:


> My first question is that if the SP switch is implemented with MOSFETS then where can you draw the gate voltage required to turn on the MOSFETs?


For S3 and S1b you can take the power from the battery/batteries they switch. For S1a you'd need to get a voltage that's sufficiently higher than the local batteries so you probably need some kind of local DC/DC too. To isolate the MOSFET's from the rest of the electronics you can connect the gates of the MOSFET's through opto-couplers, one for S1a and S1b and one for S3.



ga2500ev said:


> The second question is about the bypass switch. While using a diode is an easy solution, the added diode drops will burn off quite a bit of energy as heat. What would happen if you replaced that switch with MOSFETs? Would those MOSFETS have to support the voltage of the entire pack?


I'm not quite sure, but I think the MOSFET will have to survive HIGHER voltage than the pack voltage thanks to back-EMF since you will have to make DAMN sure SP is open before SB closes and during that time back-EMF will skyrocket to several hundred Volts, maybe even beyond a thousand Volt. It's probably easier to keep the diode because at the currents we're talking about I don't think the losses will be that big due to the diodes Vf compared to the MOSFET's Ron.

But, seriously, this is not going to be neither a good, nor cheap controller. There's a reason more or less all motor controllers out there (not just in EV's but in process industry etc) runs PWM. It's the most practical solution and done right it's very reliable. That some controllers has blown doesn't mean the concept in itself is faulty...


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## Anaerin (Feb 4, 2009)

Qer said:


> But then you will have to implement both a PWM-controller and a PWM-free controller, ending up with twice the problems...


I could be wrong, but isn't this how the Curtis controller works? It PWMs at low power requests (To vary the voltage/torque), then WOTs the PWM circuitry to full pack voltage and varies the amperage to change speed. Hence the "Violin" sound at crawling speeds.

Or have I missed the mark here?


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## Qer (May 7, 2008)

Anaerin said:


> Or have I missed the mark here?


Slightly. 

The Curtis usually PWM at 15 kHz but at start it PWM's at 1.5 kHz since there were problems with older Curtis controller blowing up if there were a major current rush. Or something like that, the lower frequency that makes the squealing is a fix on some kind of problem they had before anyway.

So it's always PWM'ing, just at different frequencies.


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## Tesseract (Sep 27, 2008)

This is not a completely bad idea but realize that it gives very granular control of the wrong parameter, too (you ideally want to control motor amps, not motor volts - motor volts will work but it will give you that jerky "golf cart" feeling).



ga2500ev said:


> ...OTOH at 16 KHz there are 2 switch transistions every 62.5 uS. Even if the switch time is only 1 uS per switch then that's a 3.2% loss all the time.


1uS per transition in this case would be exceptionally sloppy. The rule of thumb is that the ideal total switching time should be around 0.5-1% of the period because that strikes a good balance between overshoot/ringing and switching losses. Also, one big advantage if the load is inductive (ie - a motor) is that the voltage and current hardly overlap at switch turn-on.

FWIW, the switching time per transition on my controller protoype is 150nS at 680A of load current, or a very respectable 0.48% total.




ga2500ev said:


> Also if you implement with semiconductor switches, then you can PWM those switches to limit the torque initially then have them switch permanently once the vehicle is moving.


If PWM will be used at some point then why bother with the rest of the setup?




ga2500ev said:


> Qer, I think you missed my point. At the end I was asking how can you implement the structure of these types of controllers using semiconductor switches? So you use MOSFETS instead of actual contactors.
> 
> It's the structure of the controller that I want to keep, not the actual parts. I don't want to use actual contactors because frankly they cost too much, are too noisy, and as you pointed out, require maintenance.


No problem with this, but realize that each bank of MOSFETs used to replace a contactor will need to have isolated gate drive and while they do not need to be switched quickly, the timing of the turn off of one "contactor" and the turn-on of another needs to be carefully coordinated. I suspect that in the end your parts cost will be the same or more as a goood PWM chopper design but with much worse throttle response to show for it. Not saying it can't be done or that it isn't worth thinking about, just that it does not pass muster with me on first glance.


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## ga2500ev (Apr 20, 2008)

Qer said:


> Well, if you're using MOSFET's as you suggest further down there will be a lot of Ron's in the chain which will result in rather substantial losses as well. I'm not convinced it's an improvement. Also, I believe our numbers for our prototype is better than 3.2% losses, but I'll leave that to Tesseract to sort out if he likes.


Take a read on the BatPack numbers for Ron. Specifically:



> I made a leap of logic when I discovered that the on resistance of MOSFETs increased with the BVds to the power of 2.8. This factor approximately was true for all venders. Ok, so with the use of 500 Volt MOSFET used in the 250 Volt switcher vs. the 250 Volt MOSFETs used in the 125 Volt switching controller I would need about 7 times as many transistors connected in parallel.


If these number are even close to true, then that means that sums of the Rons of the lower voltage MOSFETS would be much less than the Ron for the PWM controller.



> But then you will have to implement both a PWM-controller and a PWM-free controller, ending up with twice the problems...


The difference is putting your eggs in a single high voltage basket as opposed to multiple lower voltage ones. with significant differences in switching speed. 

Also the pseudo PWM I'm talking about is nothing more than adjustable current limiting, of which overcurrent protection is going to be required anyway. We all know that torque is directly related to current.

Paul Homes made an interesting observation in the development of his open source PWM controller. You can find the thread here:

http://ecomodder.com/forum/showthread.php/paul-sabrinas-cheap-144v-motor-controller-6404.html

He observed that you can get smooth acceleration simply by limiting the percentage of current to the percentage of throttle. So if the throttle is at 10% of max, limit current to 10% of max.

The same can be done for a contactor/batpack type controller at low speeds. Of course the obvious way to pull this off with MOSFET switches is to PWM them during that period. Once reach 100% of the lowest battery level valued subpack, you can disable the PWM and just start switching normally.



> Well, it's doable but considering the amount of contactors/MOSFETs/whatever you'll need, it's not going to be cheap. The simplest approach is probably to use solid state relays but they don't come cheap. Especially not if they need to handle DC. How many steps do you want the controller to handle? If it's enough with 3 power steps (1/4, 1/2 and full pack voltage) you still need 9 switches that each can handle max current.


The number of switches depends on the configuration. In the rectactor config you'd need 7 switches to switch 4 modules. In the BatPack config you'd only need 3 modules and therefore 3 switches.

Now we're talking! Again take a look at BatPack argument. The lower valued MOSFETS have a lower Ron. So each can carry more current at their rated voltage.

I'd like to see some holes poked into that argument. Is it true that the RDSon jumps 7 times when you double the max voltage of the MOSFET? Let me go see for myself. I'm going to look up the RDSon for a 50V, 100V, and 200V MOSFET in the same family. Be right back.

Took a minute. Doesn't seem to hold true. I took a look at International Rectifier HexFETs on digikey. Only took items that were actually in stock. Here's what I found:

irfp064npbf 55V 8 mOhms RDSon 59A $2.82
irfp4410zpbf 100V 7.2 mOhm 97A $3.70
IRFSL4227PBF 200V 26 mOhms 62A $4.14

While the 200V part has a much higher RDSon, the 55V and 100V parts are virtually identical. 


> Looking at Digikey the strongest solid state relay for DC I can find handles max 100 Ampere and 60 Volt (which, to say the least, is a bit on the low side) and they cost $120. Each. They have a MOSFET that can handle 200 Volt 580 Ampere and it "only" cost $145, but you still need at least 9 of them. You can probably find much cheaper on E-bay, but in case you want a little more than three speeds the amount of MOSFET's will increase drastically and thus also the cost.


But you don't need 200V mosfets. That's the whole point. You can do the whole thing wth 55V or 100V mosfets with the prices I outlined above. BTW the item you referenced isn't in stock. That makes it made of unobtanium. Actually $145 for a 200V 580A MOSFET module isn't too bad a price.

But back to the point. If we took the 100V parts and derated to half max power, then for 400A we'd need 400A/50A = 8 parts per switch. In the batpack config with 3 switches that would be 24 parts. Digikey breaks the price to $1.95 at 10 parts. So the total cost would be about $50 for the switches.




> Then there's another problem involved, if you use silicon you need to limit the current and make damn sure you don't exceed the rating. If you do it by starting to PWM when things go rough you will enter that twilight zone where spikes and heat dissipation blow things up for you and if you do it by switching down to a lower voltage you will never be able to get maximum current out of your pack and the performance will suffer.


overcurrent is solved the same way as a PWM controller: You PWM all the switches. You don't want to lower the voltage because then that raises the current required on the remaining switches. So you cut off the power until the current drops and turn on all the switches again.

But that's an overcurrent condition and shouldn't happen under normal circumstances.




> But it's definitely doable, just not very practical. However, to answer some of your questions:
> 
> 
> 
> ...



All the discussion that I've seen here makes PWM seem undoable. And it's all related to trying to switch the full pack voltage at 100s of amps at 15 kHz+.

Qer, take your focus away from the rectactor for the sake of discussion and focus on the BatPack. Imagine a 144V 500A controller that consist of 6 subpacks: 2 12V, 2 24V, and 2 36V packs stacked serially. It delivers voltages in 12V increments from 0-144V giving 13 steps.

Now presuming that the you implement both switches using MOSFETs you'd need 20 per module. 120 MOSFETS. At $1.52 each that would run about $170.

Of course you still need the freewheeling diode to protect the electronics.

ga2500ev


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## ga2500ev (Apr 20, 2008)

Tesseract said:


> This is not a completely bad idea but realize that it gives very granular control of the wrong parameter, too (you ideally want to control motor amps, not motor volts - motor volts will work but it will give you that jerky "golf cart" feeling).


I'm aware. I can live with the a reliable jerky golf cart feeling.



> 1uS per transition in this case would be exceptionally sloppy. The rule of thumb is that the ideal total switching time should be around 0.5-1% of the period because that strikes a good balance between overshoot/ringing and switching losses. Also, one big advantage if the load is inductive (ie - a motor) is that the voltage and current hardly overlap at switch turn-on.


Good to know.



> FWIW, the switching time per transition on my controller protoype is 150nS at 680A of load current, or a very respectable 0.48% total.


Are you have any overshoot issues?



> If PWM will be used at some point then why bother with the rest of the setup?


PWM is going to have to involved because of the semiconductors. With contactors the amps are not as big an issue. With MOSFETS you overamp them and they smoke.

So you are going to have to have overcurrent control which means turning the switches on and off, a form of PWM.

You'll get the same effect if you adjust the current limit at low throttle positions.

But once you get to speed, the switching is minimal.



> No problem with this, but realize that each bank of MOSFETs used to replace a contactor will need to have isolated gate drive and while they do not need to be switched quickly, the timing of the turn off of one "contactor" and the turn-on of another needs to be carefully coordinated. I suspect that in the end your parts cost will be the same or more as a goood PWM chopper design but with much worse throttle response to show for it. Not saying it can't be done or that it isn't worth thinking about, just that it does not pass muster with me on first glance.



That's the kind of feedback I'm looking for. But my primary criteria are DIYability and reliability. I'm pretty sure I can stack a 12V, 24V and 36V module together and get a 6 speed test setup that switches at 100 Hz. OTOH I'm almost certain that this guy Paul over at ecomodders who is trying to put together a DIY PWM is going to have his project blow up.

http://ecomodder.com/forum/showthread.php/paul-sabrinas-cheap-144v-motor-controller-6404.html

There's a vast difference between switching at 4, 8 or, 16 kHz and switching at 100 Hz or less. BTW a $5 microcontroller would have no problem sequencing switching.

Every thread that I've read here on PWM makes it clear that there are nuances that makes it very difficult to DIY.

I need a controller that works, that I can build myself, and that won't cost a mint to build. In all the time I'm been on the forum, no PWM controller meets that standard.

Hence my discussion on the alternatives.

ga2500ev


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## Qer (May 7, 2008)

This mad idea of yours has been nagging in the back of my head for a few days, and I have some thoughts that you might like (or not):



Skip the MOSFETs. Let's say you have 4 groups of batteries you can swap around with the MOSFETs, that means that if you go full throttle and run at 120 Volt, 500 Ampere (numbers out of a hat just as an example) and you have top notch MOSFETs with Ron of only 5 mOhm that still means that you will lose 500 Ampere * 5 mOhm * 3 MOSFETs = 7.5 Volt. That's 3.75 kW heat you have to cool and it means your efficiency is down to 94%!
Don't PWM. If you PWM you'll have the same problems as any other PWM-controller plus additional problems as well. If you really want to do a sledge hammer and crowbar controller, do as they did before the silicon era and use a resistor for soft start if you can't switch down the Voltage enough.

My suggestion is that you use contactors that can handle, say, 1000 Amps as long as they don't have to make/break the current (probaby cheaper than contactors that can make/break all that current) for reorganizing the battery pack and then you use one bad-ass contactor that CAN make/break serious current as the major on/off-switch. If you use a micro controller (or maybe build some relay logic to match the contactors ) that can read the contactor position by the help of a monitoring switch on each (sorry, don't know what they're called in english) then a switching sequence would look like this:



Break master contactor
Reorganize the battery pack connections
Wait until all contactors are secured in the right position
Wait a little longer to make sure there's no contact bounces that can arc and weld
Switch on master contactor

The reorganization of the pack has to be done carefully (and possibly in several sequences to avoid any risks) to make sure that a slow, or stuck, contactor doesn't result in for example two parallel connected parts of the pack gets connected with two serial connected parts. I'd recommend fuses for every stand alone part of the pack to avoid big badabooms...

I'm still not convinced this is a good idea or that it'll be efficient or cheap, but it will definitely be a controller that almost anyone can build, maintain and repair. However, all those current spikes will probably bring havoc with your peukert effect and ruin your range...

So, that's how I think a DIY-or-bust electro-mechanical controller should be built. Don't forget to make sure the sound comes through loud and clear if you ever upload a video to YouTube! It's definitely going to be more impressive sounding than the Curtis squeal.


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## ga2500ev (Apr 20, 2008)

Qer said:


> This mad idea of yours has been nagging in the back of my head for a few days, and I have some thoughts that you might like (or not):


Thanks for coming back.


> Skip the MOSFETs. Let's say you have 4 groups of batteries you can swap around with the MOSFETs, that means that if you go full throttle and run at 120 Volt, 500 Ampere (numbers out of a hat just as an example) and you have top notch MOSFETs with Ron of only 5 mOhm that still means that you will lose 500 Ampere * 5 mOhm * 3 MOSFETs = 7.5 Volt. That's 3.75 kW heat you have to cool and it means your efficiency is down to 94%!




[email protected]=60KW=80.5 HP. Probably unrealistic. The efficiency won't be that bad by a long shot.


> Don't PWM. If you PWM you'll have the same problems as any other PWM-controller plus additional problems as well. If you really want to do a sledge hammer and crowbar controller, do as they did before the silicon era and use a resistor for soft start if you can't switch down the Voltage enough.


I agree with this. This falls in line with the KISS principle. Just keep it simple.



> My suggestion is that you use contactors that can handle, say, 1000 Amps as long as they don't have to make/break the current (probaby cheaper than contactors that can make/break all that current) for reorganizing the battery pack and then you use one bad-ass contactor that CAN make/break serious current as the major on/off-switch. If you use a micro controller (or maybe build some relay logic to match the contactors ) that can read the contactor position by the help of a monitoring switch on each (sorry, don't know what they're called in english) then a switching sequence would look like this:
> 
> 
> 
> ...


This has some promise. Using LEV200 contactors:

http://www.evsource.com/tls_relays.php

And diode modules like this INXS:

http://theelectrostore.com/shopsite_sc/store/html/diode-meo450-12da-ixys-meo-450-12-da-fred.html

One can build subpacks for about $130 each along with the $200 for the main contactor, resistor contactor, and freewheeling diode module. So a 2 module 3 speed controller can be put together for under $500 consisting of 4 contactors and 3 diode modules. By doing a serial only setup instead of a serial/parallel setup adding another module only requires another contactor and diode instead of adding two serial/parallel subpacks each with a contator and 2 diodes along with the contactor and two addition diodes to tie the two larger modules together.

A MOSFET setup would require 10 mosfets per subpack along with the isolated gate driver. About half the price of a contactor along with silent operation.



> I'm still not convinced this is a good idea or that it'll be efficient or cheap, but it will definitely be a controller that almost anyone can build, maintain and repair. However, all those current spikes will probably bring havoc with your peukert effect and ruin your range...
> 
> So, that's how I think a DIY-or-bust electro-mechanical controller should be built. Don't forget to make sure the sound comes through loud and clear if you ever upload a video to YouTube! It's definitely going to be more impressive sounding than the Curtis squeal.



Reliable and doable are the first goals. The main contactor is a wash because any system requires it.

ga2500ev


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## Tesseract (Sep 27, 2008)

ga2500ev said:


> ...By doing a serial only setup instead of a serial/parallel setup adding another module only requires another contactor and diode instead of adding two serial/parallel subpacks each with a contator and 2 diodes along with the contactor and two addition diodes to tie the two larger modules together.
> 
> A MOSFET setup would require 10 mosfets per subpack along with the isolated gate driver. About half the price of a contactor along with silent operation.


Don't forget that each mosfet bank will need an isolated power supply (eg - prepackaged dc-dc converter module such as this one from DigiKey:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=102-1365-ND

And the optoisolated gate drive for them. Even though you are switching at a low frequency you still need to switch the gates on and off quickly. The peak current always depends on the total gate charge and how fast you charge or discharge it 

Also, to briefly answer a question from a previous post by you... yes, there is a significant overshoot when turning the IGBT off so rapidly in the prototype controller. Specifically, the overshoot has maxed out around just under 2x the dc bus voltage. But the prototype uses a single 1500uF inverter-grade capacitor on the input so it isn't exactly optimal. Of course, using a 600V IGBT in a 200V system (the max my test setup can accommodate at the moment) relieves a lot of the pressure to optimize the layout, too 

Okay, one last comment. Those Tyco contactors are a real bargain in my opinion. I honestly don't think the cost savings going with a bank of MOSFETs is worth the additional headache and complexity to get such to work. Furthermore, the contactors don't care (as much) about spikes, are far more tolerant of overcurrent and don't need a pc board nor a bunch of isolated heat sinks like the MOSFETs will.

EDIT: one other thing - each diode in the series string configuration (I think you referred to it as the "BatPack" setup) can be rated for just the individual battery voltage. You don't need a high speed FRED here, nor the high voltage. Regular diodes, or Schottkys, would be better (especially Schottkys, as they have such a low forward voltage drop... kind of pricey, though). Don't forget to connect a resistor in parallel with each Schottky to enforce voltage sharing in a series string.


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## Anaerin (Feb 4, 2009)

I'm (very) interested in this "Battery Shuffle Controller" system.

My question is, do the ratings on MOSFETs/IGBTs have to be for the circuit as a whole, or would sizing them for the section they are dealing with work?

Let's take a (small) example of 8 12v/100Ah packs/strings/nodes, connected in a kind of "Mesh" network, with a controller that can connect them in:

1x8 pack (12v, 800Ah)
2x4 packs (24v, 400Ah)
4x2 packs (48v, 200Ah)
8x1 packs (78v, 100Ah)

Would each MOSFET in the system have to be able to cope with the full 78v, 800A, or would each only have to deal with the 12v, 100A on it's local section?

In other words, If I had:

```
|       /[U]-[/U]-[U]-[/U]-[U]-[/U]\     |       /[U]-[/U]-[U]-[/U]-[U]-[/U]\ 
-----| |----(-+ | +-)----| |----(-+ | +-)---
     |       \  |  /     |       \  |  /
```
(Sorry about the diagram)

Would each MOSFET have to handle all the voltage, or just the difference between the cells?


----------



## Qer (May 7, 2008)

ga2500ev said:


> Thanks for coming back.


I never left. 



ga2500ev said:


> [email protected]=60KW=80.5 HP. Probably unrealistic. The efficiency won't be that bad by a long shot.


Possibly, but there will still be several Ron in series that will gnaw on your power output so I doubt you'll be able to get it as efficient as a PWM controller.

In a MOSFET-controller (like, for example, Kelly) the MOSFETs are in parallel which lowers the Ron instead, so I doubt this controller will be more efficient in the end.

On the third time, throw in some extra batteries and we call it even. 



ga2500ev said:


> A MOSFET setup would require 10 mosfets per subpack along with the isolated gate driver. About half the price of a contactor along with silent operation.


As long as you're aware that MOSFETs might blow because of over temp, over current and spikes and that this is the price you pay for leaving the electro-mechanical path behind. Don't forget to add the cost for heat sinks, drivers and small DC/DC's when you calculate the price.



ga2500ev said:


> Reliable and doable are the first goals. The main contactor is a wash because any system requires it.


True, but usually you don't break/make with current and the main contactor is only operated when PWM is zero. So you might need a tougher breed to handle this controller.


----------



## ga2500ev (Apr 20, 2008)

Tesseract said:


> Don't forget that each mosfet bank will need an isolated power supply (eg - prepackaged dc-dc converter module such as this one from DigiKey:
> http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=102-1365-ND
> 
> And the optoisolated gate drive for them. Even though you are switching at a low frequency you still need to switch the gates on and off quickly. The peak current always depends on the total gate charge and how fast you charge or discharge it


It's still unclear what the relationship of the DC/DC module to the MOSFETs and the battery bank would be. As shown the source of the MOSFET is connected to the positive terminal of the battery bank, and the drain is left open to connect to the next bank above it. The gate needs to be above the source in order to turn the MOSFETS on. So that means that the virtual ground of the DC/DC converter needs to be the positive terminal of the battery bank. So I presume that means that each converter has to steal power from the battery bank above it in the chain?

If that's the case then why would I need a DC/DC converter at all? Why can't there be a driver that uses the source connection as a virtual ground and pull power directly from the battery bank above without isolation? A optoisolator would still be needed to trigger the driver, but I can't see clearly the need for the DC/DC converter when it's going to have to steal power from the bank above anyway.

Would the arrangement work low side? Something like this?


```
|
         |
 +----+
  |      |
B1   D1
  |      |
  +S1+
         |
         |
```
From a driver standpoint this makes more sense because the virtual ground is at the connection point of S1 and D1, with B1 available to provide power to the gate to turn the switch on.

Or am I just completely missing the point?



> Okay, one last comment. Those Tyco contactors are a real bargain in my opinion. I honestly don't think the cost savings going with a bank of MOSFETs is worth the additional headache and complexity to get such to work. Furthermore, the contactors don't care (as much) about spikes, are far more tolerant of overcurrent and don't need a pc board nor a bunch of isolated heat sinks like the MOSFETs will.


So the only real downsides that I see are the obvious clicking as the contactors make/break and that there is a clear limited lifetime (100k mechanical, 50k useful at 90% capacitive precharge) to the number of make/break contacts that can be made.

What I'm getting from this thread is that MOSFETs are hard to deal with no matter how you arrange them. I was figuring that if you limited the switching frequency and lowered the voltage being switched, that dealing with MOSFETs would become less difficult. But it seems that the same headaches exists even if you are switching a lower voltage at a much smaller frequency.

How about IGBTs? I know that there's going to be a major efficiency hit due to the large voltage drop. But would using a IGBT module simplify construction any? Could the IGBT be placed low side in the configuration above? I know it doesn't make much sense to use 600/1200V IGBTs to switch 24 or 36V. But contactors will wear out and MOSFETs seem to be to persnickety.

Is it too much to ask to have the semiconductor equivalent of a contactor? Something that can switch a few hundred volts @ a few hundred amps, has isolated controls, doesn't cost a mint, and is reliable?

I'm used to just throwing transistors and MOSFETs at low voltage/low current problems and having them work. Relays are fine for low frequency switching of higher voltage/higher amp tasks. But EV controllers are like learning the black arts, with the requisite black smoke.



> EDIT: one other thing - each diode in the series string configuration (I think you referred to it as the "BatPack" setup) can be rated for just the individual battery voltage.


Good to know. OTOH the diode has to carry the entire rated current of the controller though, right? The Ixys 1200V FRED modules are rated for 450A and cost less than the comparable studs from Vishay I found on Mouser:

http://mouser.com/Search/Refine.aspx?Keyword=844-240U60D



> You don't need a high speed FRED here, nor the high voltage. Regular diodes, or Schottkys, would be better (especially Schottkys, as they have such a low forward voltage drop... kind of pricey, though).


diodes have a positive temp coefficient, so they cannot be easily paralleled. So we're talking about a single unit, right? The FRED seems to be the best buy even though it's way overspeced.



> Don't forget to connect a resistor in parallel with each Schottky to enforce voltage sharing in a series string.


I presume that the resistor should be at the current limit for the diode or thereabouts? So if we're talking about 12V @ 400A then it should be 30 mOhms per 12V in the pack? And what exactly am I supposed to do about the 4.8 kW rating?

Design ideas are fun. Engineering is not. That's why I'm an embedded systems guy, not a engineer.

ga2500ev


----------



## ga2500ev (Apr 20, 2008)

Anaerin said:


> I'm (very) interested in this "Battery Shuffle Controller" system.
> 
> My question is, do the ratings on MOSFETs/IGBTs have to be for the circuit as a whole, or would sizing them for the section they are dealing with work?


In theory it's only the section that the MOSFETs are switching. But in practice it's simple enough to get MOSFETs rated at the voltage of the pack.



> Let's take a (small) example of 8 12v/100Ah packs/strings/nodes, connected in a kind of "Mesh" network, with a controller that can connect them in:
> 
> 1x8 pack (12v, 800Ah)
> 2x4 packs (24v, 400Ah)
> ...


It's 96V, not 78V.




> 800A, or would each only have to deal with the 12v, 100A on it's local section?


If it's meshed like you stated, then it's going to be arranged in a rectactor type tree, where pairs of batteries are grouped together into 12/24V subpacks, then two pairs of those are grouped into 24V/48V subpacks, finally the two 48V subpacks can be switched in a 48V/96V arrangement.

In the 12V configuration, no switches are on, only diodes are conducting. So the diodes would need to be rated at the full amperage, but switches do not.

The 12/24V switches would need to be rated at 400A
The 24/48V switches @ 200A
The 48V/96V switch @ 100A

But you can parallel MOSFETs to get the amperage you need. So it's just a question of how many MOSFETs you need in each switch.

As for voltage each switch needs to handle the higher voltage that the switch is switching. But easily solved using 100V MOSFETS all the way around.

ga2500ev


----------



## ga2500ev (Apr 20, 2008)

rmay635703 said:


> Not to throw a wrench in here but another way of limiting current and reducing Peukert (at least I'm told so) is to have a suido "tesla" switch setup which is very similar to the batpack with one major difference.
> 
> In my case I have 9 batteries 8v each. All would be wired to the controller individually 1st speed would be 5 batteries in series positive (aka discharge) and 4 is series negative (aka recharge), batteries typically switch out sequentially aka you don't leave batteries in the charge position more than 1 us meaning switching speed would be around 1/9us for 9 batteries. 2nd speed would be 6 in discharge position 3 in recharge position, you could obviously PWM between one state and another to get intermediate speeds.
> 
> ...


The real problem is that charging converts a portion of the energy to heat. Which means that it's wasted.

So there's no effective point in using one battery to charge another. The energy would be much better spent going to the motor.

ga2500ev


----------



## ga2500ev (Apr 20, 2008)

I really hate the fact that vbulletin won't keep the embedded quotes. Makes it real hard to hold a thread. I'll reinsert.



Qer said:


> ga2500ev said:
> 
> 
> > [email protected]=60KW=80.5 HP. Probably unrealistic. The efficiency won't be that bad by a long shot.
> ...


Is there a direct correlation between the switch time and the switching loss? Or is it a function of the frequency. Tesseract stated that his controller's switch time is about 0.5% of the period. So does that automatically translate into a 0.5% loss of efficiency?


Qer said:


> ga2500ev said:
> 
> 
> > A MOSFET setup would require 10 mosfets per subpack along with the isolated gate driver. About half the price of a contactor along with silent operation.
> ...


Overcurrent/overtemp: why can't you just turn them off when this happens?

spikes: doesn't the freewheeling diode protect against these?

See my other post on the DC/DC


Qer said:


> ga2500ev said:
> 
> 
> > Reliable and doable are the first goals. The main contactor is a wash because any system requires it.
> ...


I don't think so. The main contactor is the first contactor on and the last contactor off. The inrush current would be limited to the inline resistor. Also you technically would only need it with the rectactor arrangement because with all the other switches off, the rectator still conducts the lowest pack voltage minus the diode drop.

But in the BatPack arrangement of serial subpacks, when all the switches are off, there's no voltage/current.

I think you're thinking of your arrangement of doing make/break of the main contactor at load. Then in that case you are probably right.

I think all of the discussion has refined my point. I understand from a structural standpoint that a PWM controller is theoretically easy to construct: put one honking big switch between a full pack and the motor and turn it on and off really fast. But it's also clear there are a ton of design nuances related to switching on and off the pack really fast.

My question is how are things different of you only switch the switch occasionally. You example above Qer illustrates the point: what would happen if you replaced the main contactor with a MOSFET switch? It has switch under load, but it doesn't have to switch often (50 Hz or slower). How is that any different than a MOSFET switch PWMed at 16 kHz?

If it's no different from a design standpoint, then most likely this thread is dead. But if the design process is simplified because the switching is much less frequent, then there is a glimmer of hope.

I always envisioned PWM like banging a hammer on the MOSFETS. If you bang a lot less often, then it should not be as hard on them.

I'm not worried about the control side. Other than fast current transients, a typical microcontroller can easy handle all of the timing, sequencing, voltage and current monitoring issues. I'm just trying to understand what design differences exist when you are turning on MOSFETs and you know they are going to be on for hundreds of milliseconds as opposed to turning on a MOSFET and you know they are going to be switched off in 30 uS, and then slammed on again 30 uS after that.


ga2500ev


----------



## Tesseract (Sep 27, 2008)

ga2500ev said:


> It's still unclear what the relationship of the DC/DC module to the MOSFETs and the battery bank would be. ...


Simple: to turn on an N-Ch. MOSFET you have to make the gate approx. 10V more positive than the source. The only practical way to do that with a series connected string of MOSFETs is to have a floating power supply for each one. It is also possible to use a charge pump as long as the MOSFETs do not stay on or off for prolonged periods of time... ie, they are always switching, not static switches.




ga2500ev said:


> Why can't there be a driver that uses the source connection as a virtual ground and pull power directly from the battery bank above without isolation?


Theoretially you could do something like this, but the virtual ground will have to source/sink several amps peak of current and you will still need at least one dc/dc converter to be able to turn on the higher (most positive) MOSFET) anyway. Also, keep in mind that the arrow in the MOSFET symbol needs to point to the more negative end of the circuit, thus you will need a P-Ch. mosfet in the circuit drawn (and it needs the gate to be made more negative than the source to turn it on, so you are in the same predicament all over again).




ga2500ev said:


> What I'm getting from this thread is that MOSFETs are hard to deal with no matter how you arrange them. I was figuring that if you limited the switching frequency and lowered the voltage being switched, that dealing with MOSFETs would become less difficult. But it seems that the same headaches exists even if you are switching a lower voltage at a much smaller frequency.


Precisely! Just because you are switching them at 100Hz instead of 16kHz doesn't mean you can let them spend dozens of uS (or longer!) in the linear region. 




ga2500ev said:


> How about IGBTs?


No difference...




ga2500ev said:


> Is it too much to ask to have the semiconductor equivalent of a contactor? Something that can switch a few hundred volts @ a few hundred amps, has isolated controls, doesn't cost a mint, and is reliable?


It's the "doesn't cost a mint" restriction that's killing you here.




ga2500ev said:


> I'm used to just throwing transistors and MOSFETs at low voltage/low current problems and having them work. Relays are fine for low frequency switching of higher voltage/higher amp tasks. But EV controllers are like learning the black arts, with the requisite black smoke.


Thanks for noticing 




ga2500ev said:


> Good to know. OTOH the diode has to carry the entire rated current of the controller though, right?


Correct, each diode carries the entire motor current.




ga2500ev said:


> diodes have a positive temp coefficient, so they cannot be easily paralleled. So we're talking about a single unit, right? The FRED seems to be the best buy even though it's way overspeced.


Diodes can be paralleled if they are all closely linked thermally, but in general, yes, you should use a single unit wherever possible.




ga2500ev said:


> I presume that the resistor should be at the current limit for the diode or thereabouts? ...


Incorrect, the resistor needs to only carry the worst case leakage current... usually a few hundred uA for FREDs but up to several tens of mA for Schottkys.


----------



## ga2500ev (Apr 20, 2008)

Tesseract said:


> Simple: to turn on an N-Ch. MOSFET you have to make the gate approx. 10V more positive than the source. The only practical way to do that with a series connected string of MOSFETs is to have a floating power supply for each one. It is also possible to use a charge pump as long as the MOSFETs do not stay on or off for prolonged periods of time... ie, they are always switching, not static switches.


So with an isolated supply you can power all of the modules with a separate 12V battery, right? You'd connect the floating ground of the isolated supply to the source terminal of the floating MOSFET and then switch the gate between that floating ground and the V+ of the isolated supply. 

So does the battery driving the isolated supplies have to be ground referenced to ground of the motor system. Or because it's floating, can it be completely isolated?

How about an alternative? The IRS2186(4) has a floating high side driver that works up to 600V. the info page is here:

https://ec.irf.com/v6/en/US/adirect/ir?cmd=catProductDetailFrame&productID=IRS21864PBF

It looks like you can connect these directly without having to have a floating supply. Can drive up to 4A of current to the gate. About the same price as the DC/DC converter and has the driver too.



> ga2500ev said:
> 
> 
> > Why can't there be a driver that uses the source connection as a virtual ground and pull power directly from the battery bank above without isolation?
> ...


Got it. And P-channels are bad news because their RDSon is much higher than corresponding N-channel parts.

Now the peak current problem. This seems to be the single area that may be a touch simpler to pull off because of more time.

From your discussions elsewhere peak current drivers are done by charging a cap with the charge that you need, then firing the charge in the cap through the gate. The power supply then recharges the cap so that it's ready for the next firing down the road. Now when you are doing this quickly then the power supply needs a high average current in order to charge the cap quickly enough to be ready for the next iteration. But when the firing frequency is low, the average current of the power supply can be much lower and it can charge the cap slower. So for example with the isolated supplies you referenced earlier, the 12V-9V DC only has a max output current of 111 mA. But as long as the driver's cap can be recharged before the next switch, then everything should be fine.

It's starting to make some sense now.



> ga2500ev said:
> 
> 
> > Mosfets are a headache!
> ...


So you have to switch fast no matter what.




> ga2500ev said:
> 
> 
> > IGBTs?
> ...


Out of the question then. Only downsides.






> ga2500ev said:
> 
> 
> > My contactor substitute requirements.
> ...


OK then humor me. Take cost off the table. What device can you get that's semiconductor based and functions like a LEV200 contactor. 320V, 500A max, built in isolated supply and driver? I've never seen anything off the shelf that functions like that.


I'll tackle the rest later.

ga2500ev


----------



## ga2500ev (Apr 20, 2008)

I'm back to finish.



Tesseract said:


> ga2500ev said:
> 
> 
> > wattage requirements for parallel resistor for the diode? Does it need to be the full amperage drop across the diode?
> ...


And I would presume that because it is paralleled with the diode, that the voltage would be the worst case voltage drop for the diode? 

If that's the case then a small high valued resistor will likely do the job.

ga2500ev


----------



## Tesseract (Sep 27, 2008)

ga2500ev said:


> So with an isolated supply you can power all of the modules with a separate 12V battery, right? You'd connect the floating ground of the isolated supply to the source terminal of the floating MOSFET and then switch the gate between that floating ground and the V+ of the isolated supply.


Correct. Just to reiterate, though, every mosfet in the stack needs its gate to be driven at least 10V higher than its source (for N-ch. types) and the easiest way to do this is to use an isolated dc-dc converter to power the optoisolated gate driver for each one (or bank). 




ga2500ev said:


> So does the battery driving the isolated supplies have to be ground referenced to ground of the motor system. Or because it's floating, can it be completely isolated?


You could power the dc-dc converter(s) from any one battery in the string, the whole stack, or a separate battery altogether. The only important requirement is that converter's output "ground" can be tied to the source of a MOSFET that is sitting on top of one or more other batteries. The elegant way to do this (well, sort of elegant) is to use a single flyback topology smps with as many secondaries as there are batteries/switches in series. The secondaries in a flyback switcher track each other extremely well because an output inductor is not needed. and the average power required to drive the gates is very low, which also suits the flyback well.



ga2500ev said:


> How about an alternative? The IRS2186(4) has a floating high side driver that works up to 600V.


You can use charge pump drivers like the IR part _as long as you switch the fets on a regular basis!_ If the MOSFETs will be on (or off!) for any length of time then a charge pump won't work.



ga2500ev said:


> From your discussions elsewhere peak current drivers are done by charging a cap with the charge that you need, then firing the charge in the cap through the gate.


Correct! The average current to drive even huge IGBTs or banks of MOSFETS is very low. That said, the driver still needs to be capable of sourcing and sinking a very high peak. Typically, this requires a bipolar transistor totem pole with MLCC and Al capacitors as close to them as possible.



ga2500ev said:


> So you have to switch fast no matter what.


Unfortunately, yes, but only to a point! Faster switching times reduce losses, but also exacerbate spikes/ringing from stray (or unclamped) inductances.




ga2500ev said:


> OK then humor me. Take cost off the table. What device can you get that's semiconductor based and functions like a LEV200 contactor. 320V, 500A max, built in isolated supply and driver? I've never seen anything off the shelf that functions like that.


Neither have I. You'll probably have to build it out of a bank of MOSFETs and an isolated driver...


----------



## order99 (Sep 8, 2008)

Please keep in mind that I am an ignorant savage whose sole knowledge of Electronics comes from repeated viewings of Metropolis... 

(GO ROTWANG!) 

Knowing the above...if I was to create a low-powered EV-say 48V-and wanted the absolute simplest and most robust controller I could create, how about this?

4 12V packs. Completely unconnected. An Amp Limiter on each battery lead for x Amps. 
4 Switches, able to withstand x+20 Amps. Switches or buttons grouped together in a single easy-to-reach panel. All leads run through a Main Contactor switch for emergency cut-offs.
1 Reversing Contactor, hooked to one of the batteries with a Resistor for 6V. The Reverse Switch underneath the Forward Switches(with a sliding panel so I can't engage both F and R simultaneously by mistake). Fuses for all leads of course.
All Switches connected to Potbox (pedal, thumb-throttle, whatever).
A 5th Battery with fuse, unconnected , just to run the dash and options.
All batteries use a separate(inexpensive!) 12V charger hooked up to a single Surge-protected Power Strip and wall plug-in.

The Theory-driver gets in, disengages the Panic Switch, hits Reverse(6V) and uses throttle. Driver hits F1 for 12V, hits throttle, then F2, F3, F4(24,36,48V). The Amp Limiters on each battery limit the Max Amp draw from each battery, the Fuses and the Panic Switch prevent terrible mishaps and individual charging prevents balancing problems. It's a given that whichever pack has the Reversing Contactor will deplete slightly faster than the rest-but since the batts no longer influence each other then they can be replaced one at a time instead of saving up for a whole pack at once.

The idea was to sort of replicate the Citicar Contactor EV, only with minimal strain to the batteries or Electronics...in practice of course, lower Voltage EVs have fairly inexpensive Controllers, so I would probably just by one for usage and(since my expertise is limited) one for replacement when it blows.

But as Proof-of concept, how much water does it hold? Feel free to point out every single flaw you find-i'm not sensitive and it's the only way i'm going to learn anything...


----------



## Qer (May 7, 2008)

order99 said:


> 4 12V packs. Completely unconnected. An Amp Limiter on each battery lead for x Amps.


How are you going to limit the current? There's no such thing as an off the shelf "Amp Limiter" that you can use like that.



order99 said:


> 1 Reversing Contactor, hooked to one of the batteries with a Resistor for 6V.


Resistors don't drop the voltage in a fashion like that. Besides, I doubt your car will even jerk with only 6 Volt on the motor.



order99 said:


> All batteries use a separate(inexpensive!) 12V charger hooked up to a single Surge-protected Power Strip and wall plug-in.


Inexpensive chargers do a bad job. Your batteries will have a rather short life span.



order99 said:


> The Theory-driver gets in, disengages the Panic Switch, hits Reverse(6V) and uses throttle. Driver hits F1 for 12V, hits throttle, then F2, F3, F4(24,36,48V).


The first battery (the one that's always used) will be discharged first which will be the limit of your range. Besides that, the current will spike every time you switch voltage which will make the discharge routine inefficient and further hurt your range.

It's doable, but it's not very efficient.


----------



## order99 (Sep 8, 2008)

"Doable, but not very efficient"? Good. At least my theoretical car didn't explode. 

When I mentioned 'Amp Limiter' before, I was thinking of those caps on the Old-school automobile Generators to prevent overloading the Starter Battery and other electric systems. My Dad, Grandad and all the local mechanics call it an Amp Limiter-I have no idea what that would be in Electronics terms...

The reason i'm curious though-if I can ever ram my spongy brain through the rest of my IT Certs (Servers are next,Yayyyyy.... )and get the money flowing again- I'm going to grab a cache of old Bicycle parts and some Coroplast for a light, Delta Trike NEV. This is where I will figure out Fiberglass forming, Shocks and Struts, Differentials, Steering etc with a VW Generator for my motor and some salvaged batts from a recycler...this will be my test bed. I expect stuff to explode. A lot. I intend for it to be an affordable series of explosions, and then i'll actually know something before the real thing. 

It's sad...I put my first Network together from scratch last week, but I can't read an Electronics schematic or hold a Soldering gun steady...

I did find something interesting in Research Mode though:

http://www.rqriley.com/urba-e.html

It mentions a 'voltage-stepper'-probably a Contactor Controller-but the original design used a CVT tranny and sensor as a kind of Controller. Does that sound feasable? It worked obviously, but I have no idea how efficiently-i'm going to grab those plans once my wallet is happy again, just to see what they're talking about!

Oh, don't forget-when you get that inexpensive, robust non-PWM Controller built? It needs to be one that somebody like me can repair enough to limp home! I am literally that Lowest Common Denominator you need to worry about-get a Controller that even I can understand, and you don't need licensed EV mechanics every 30 miles or so to get Average Joe wanting an EV anymore!

Good luck with that....


----------



## Qer (May 7, 2008)

order99 said:


> When I mentioned 'Amp Limiter' before, I was thinking of those caps on the Old-school automobile Generators to prevent overloading the Starter Battery and other electric systems.


Ah. Well, they're the completely wrong tool for the job. What they do is regulate the magnetic field in an alternator, they can't be used in a situation like this.

If you build some other current linear current limiter they'll hurt your range bad since they'll turn the excessive power into heat. Wasteful and problematic to cool.



order99 said:


> Oh, don't forget-when you get that inexpensive, robust non-PWM Controller built?


You shouldn't ask me. I'm part of building an expensive, robust PWM-controller since I believe that's the only realistic approach.


----------



## ga2500ev (Apr 20, 2008)

order99,

For some reason my post yesterday didn't make the forum.

For 48V a rectactor is your best bet. With 6 diodes and 5 contactors you can build a system that has 3 speeds (12V, 24V, 48V) and will be a rugged as they come. Also the batteries will drain evenly.

To do the serial setup you need more intelligence. That's the reason that MOSFETs would be required for a BatPack type setup. As you specified it, the F1 battery would be drained faster than the others and would then be unavailable. Also if you drain unevenly then you'll wear out parts of your pack faster than other parts, which means you'll be doing maintenance more often.

Finally what's the point of the current limiter?

ga2500ev


----------



## Technologic (Jul 20, 2008)

Tesseract said:


> Don't forget that each mosfet bank will need an isolated power supply (eg - prepackaged dc-dc converter module such as this one from DigiKey:
> http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=102-1365-ND


Or you could build a single PSU with many selectable voltage outputs?  I don't understand why each one needs that all.. just a specific voltage dividing circuit external or internal part of the controller (on a separate board)


----------



## Technologic (Jul 20, 2008)

ga2500ev said:


> OK then humor me. Take cost off the table. What device can you get that's semiconductor based and functions like a LEV200 contactor. 320V, 500A max, built in isolated supply and driver? I've never seen anything off the shelf that functions like that.


Why is this voltage/amperage necessary exactly?
Planning on needing the peak horsepower of a corvette anytime soon?

I'm still trying to understand why this is necessary at all.

if you take the example of a hybrid or other AC motor at such voltages they never see any more than a 30-40 amp current.

Have you thought about designing this controller around ultra high voltage packs with low amperages? it will cut down on "jerk" behavior the higher the voltage allowance, also most of the components will be far cheaper.

Finding a 380v x 25 amp contactor is cheap as hell, perfect for AC motors and industrial DC motors.


----------



## DIYguy (Sep 18, 2008)

U guys gotta check out the new thread on the exact controller u all need! and it costs a whopping $85! lol


----------



## order99 (Sep 8, 2008)

ga2500ev said:


> order99,
> 
> For some reason my post yesterday didn't make the forum.
> 
> ...


 We're talking about a Contactor controller with the diodes to cushion the surges, right? I have to admit I have trouble envisioning the circuit-would the rectactor you're discussing work with an odd number of packs as well (15V, 30V, 60V for example) or do the number of packs need to remain even? I'm probably getting your design mixed up with the old CityCar design (Parallel+Resistor, Parallel, Series)? This is what Dad gets for locking me out of his workshop when I was a kid, a pig-ignorant 40-year-old...

If you have any Links I could research for the Rectactor designs i'll go play with them for awhile and quit interrupting the grownups.


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## ga2500ev (Apr 20, 2008)

Technologic said:


> Why is this voltage/amperage necessary exactly?


Two reasons:

1) It's the specification for a commonly available contactor.

2) At that voltage/amperage, reasonable controllers can be built.



> Planning on needing the peak horsepower of a corvette anytime soon?


Nope see above. Rugged and reliable gets build by overspecing.



> I'm still trying to understand why this is necessary at all.


Because I've been here for nearly two years and no one has come up with a reliable easy to build PWM design. So I'm starting to think that it cannot be built. Tesseract agreed with me when I said that designing PWM controllers is a black art with black smoke.

Everyone hates contactor type controllers. The problem is that they work and they are simple to build.

I've gotten from Tesseract and Qer that PWM controllers are the best. But building one seems to be out of reach even though structurally they are simple.

I'm determined not to pour thousands of dollars into building an EV. You're talking to a guy that driving around in a daily driver that I pulled out of someone's driveway for $100 USD and fixed the master cylinder that was causing it to lock up on the road. To me cars are transportation, and need to be cheap transportation at that. My screen name probably needs to be cheap-SOB-EV.

I need cheap, reliable, safe, and DIY. Nothing that I have read indicates that any PWM controller design meets those requirements. We have folks like risto80 begging for a design that he can build. No one has ponied up. 

The BatPack design is modular, simple, and relatively inexpensive. If one switch blows out, the controller can continue to function. If one subpack gets drained, you can still get home. That's reliable. You don't need a ton of high voltage MOSFETs. You don't need a super high powered driver because you are not pounding the switch at 16 Khz.

This is supposed to by a DIY forum. But then it comes to controllers, there's little DIY going on. The expectation is that you're going to spend $600-$800 USD for a crappy controller that will need to be RSDed or $1400-$1500 for a reliable controller. Neither is an acceptable option.

Until someone comes up with a simple reliable PWM design that takes a single IGBT and can drive 144V at 500-600A and doesn't take a magician to build, then PWM isn't worth discussing for DIY.



> if you take the example of a hybrid or other AC motor at such voltages they never see any more than a 30-40 amp current.
> 
> Have you thought about designing this controller around ultra high voltage packs with low amperages? it will cut down on "jerk" behavior the higher the voltage allowance, also most of the components will be far cheaper.
> 
> Finding a 380v x 25 amp contactor is cheap as hell, perfect for AC motors and industrial DC motors.


Nope. The cost of the contactor may be cheap, but the cost of the motor? Out of the stratosphere. Also AC motors would be 3 phase, which requires a much more sophistocated controller while the industrial DC have a fixed RPM.

It's not a workable setup.

ga2500ev


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## ga2500ev (Apr 20, 2008)

order99 said:


> We're talking about a Contactor controller with the diodes to cushion the surges, right?


No. The purpose of the diodes in a rectator and in the BatPack serial setup is to provide a bypass for the batteries.

Go back and take a look at the diagram in post #1 of the thread. The diodes replace switches S1a and S1b so that when switch S3 is off, the two batteries are connected in parallel. When switch S3 turns on, the batteries are connected serially and the two diodes are bypassed.


> I have to admit I have trouble envisioning the circuit-would the rectactor you're discussing work with an odd number of packs as well (15V, 30V, 60V for example)


That's not odd packs, just odd pack voltages. The key point is that all the batteries have to be the same voltage in the rectactor setup. So 12V batteries make a lot of sense.

They are organized into a binary tree. So the number of packs has to be a power of 2 (2,4,8, 16, etc.)



> or do the number of packs need to remain even? I'm probably getting your design mixed up with the old CityCar design (Parallel+Resistor, Parallel, Series)? This is what Dad gets for locking me out of his workshop when I was a kid, a pig-ignorant 40-year-old...


Same design from what I understand.




> If you have any Links I could research for the Rectactor designs i'll go play with them for awhile and quit interrupting the grownups.


Everything I've found has been related to Lee Hart and the EVDL. I can't find the post where he posted a 4 pack rectactor and the 2 pack one is shown in post #1 of the thread.

Try searching on 'Lee Hart rectactor' and review the posts that come up.

ga2500ev


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## ga2500ev (Apr 20, 2008)

Technologic said:


> Or you could build a single PSU with many selectable voltage outputs?  I don't understand why each one needs that all.. just a specific voltage dividing circuit external or internal part of the controller (on a separate board)


Having individual floating isolated supplies makes it easier to build in a modular fashion because the supplies are independent of one another.

It turns out that not only are the isolated supplies unnecessary but the Internation Rectifier application note #978:

http://www.irf.com/technical-info/appnotes/an-978.pdf

suggests that they could be a bad idea because of spurious turnon. The AppNote is very useful. It has discussions about using the bootstrap cap to get the gate voltage, how to drive higher current modules, and most importantly how to setup to drive a switch indefinitely using a CMOS 555 based charge pump.

It looks like the process just got simpler.

UPDATE: Or not. The appnote points out that the Source needs to be grounded for the bootstrap cap to charge. So it looks like the separate floating isolated supply is in fact the best route.

ga2500ev


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## Tesseract (Sep 27, 2008)

ga2500ev said:


> This is supposed to by a DIY forum. But then it comes to controllers, there's little DIY going on. The expectation is that you're going to spend $600-$800 USD for a crappy controller that will need to be RSDed or $1400-$1500 for a reliable controller. Neither is an acceptable option.
> 
> Until someone comes up with a simple reliable PWM design that takes a single IGBT and can drive 144V at 500-600A and doesn't take a magician to build, then PWM isn't worth discussing for DIY.


Hmmm... I have to admit I got pretty ticked off the first time I read your post, but this forum *is* called _DIY_electricar, so I'll allow that you have a point here. That said, I have a point too, one I have mainly not expressed despite many occasions to do so, so I would now greatly appreciate it if you took a moment to consider things from my perspective as someone building a motor controller for commercial purposes.

First off, I think it is more than just a tad ironic to complain about how much motor controllers cost on the one hand _and_ that there are no "good DIY designs" out there on the other! Doesn't that tell you right there that _it really isn't very easy to design one of these things in the first place?_ I've been working 7 days a week on a controller design since last September and Qer, who is writing the firmware, joined the effort not too long afterwards. Both of us are working now in exchange for a portion of the profits later. In other words, pretty much for free at this point in time. I have been receiving a modest stipend of $2000 per month to, literally, pay the bills (and which will be deducted from my future profit share, btw) but that rather pales in contrast to what I could have billed for my time thus far (at the going rate of $50-$100 per hour, somewhere north of $50k at least).

Some people - especially on that ecomodders forum - expect folks like me to give away that effort for *free*. Ain't gonna happen. Oh, and it's not because of a few lost sales from DIY'ers that concerns us, mind you, it's from others outright ripping us off. And before anyone mentions the "creative commons" type of IP licenses (like GPL) as a means to protect ourselves from that sort of theft, do keep in mind that China is not exactly known for respecting the intellectual property of others...

One last thing... there are some people here who have a tremendous depth of knowledge that was earned through years of hard work, self-study (and even formal education). I am thinking, for example, of _major_ when it comes to motors or _Qer_ when it comes to programming (I can attest that he knows his stuff... his code is operating my controller prototype right now, and there have been *no* issues with his work). Respect that knowledge by not assuming you are entitled to its full benefit.

</rant>


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## Technologic (Jul 20, 2008)

Tesseract said:


> Hmmm... I have to admit I got pretty ticked off the first time I read your post, but this forum *is* called _DIY_electricar, so I'll allow that you have a point here. That said, I have a point too, one I have mainly not expressed despite many occasions to do so, so I would now greatly appreciate it if you took a moment to consider things from my perspective as someone building a motor controller for commercial purposes.
> 
> First off, I think it is more than just a tad ironic to complain about how much motor controllers cost on the one hand _and_ that there are no "good DIY designs" out there on the other! Doesn't that tell you right there that _it really isn't very easy to design one of these things in the first place?_ I've been working 7 days a week on a controller design since last September and Qer, who is writing the firmware, joined the effort not too long afterwards. Both of us are working now in exchange for a portion of the profits later. In other words, pretty much for free at this point in time. I have been receiving a modest stipend of $2000 per month to, literally, pay the bills (and which will be deducted from my future profit share, btw) but that rather pales in contrast to what I could have billed for my time thus far (at the going rate of $50-$100 per hour, somewhere north of $50k at least).
> 
> ...


I don't think anyone questions that time is worth something in such circumstances, all professionals of any type tend to demand high wages for their efforts.

To assume that you would have made $50-100/hour designing such a controller is a bit silly, especially in today's marketplace. Granted in the end your R&D will be much cheaper than if a company just outsourced it, but that's namely because there's only 2 people involved, without a limited time frame.

Your design would be considered the "top end" of the spectrum of motor controllers (considering it's voltage/amperage rating) and would be something stuck into a 250kw race car more so than a daily EV from what I've been able to reason out.

The problem I'm encountering seeing DC PWM controllers over $1000 is that AC motor controllers like 96v 300a Zapis etc...are the same price.

3 phase AC design is a few orders of magnitude more complicated (from schematics I've seen), yet there are reliable controllers with regen out there for less than the lowest line Zillas.

I think Kelly's prices are more on track, the problem is reliability I suppose with some older models being overrated. 

I actually think some of kelly's prices are too much... go figure. In my application, and certainly in most production/lightweight EVs, over 120v and 400a is probably not going to be necessary for DC.

Such an expensive, unbreakable, IGBT controller would be for sports cars (though even they would use AC motors). I think a $2000, 400v x 600amp 3 phase AC controller would be a better controller build option for sales volume. Such a controller would probably be leased out to a lot of major car companies to save R&D.


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## ga2500ev (Apr 20, 2008)

Tesseract said:


> Hmmm... I have to admit I got pretty ticked off the first time I read your post, but this forum *is* called _DIY_electricar, so I'll allow that you have a point here. That said, I have a point too, one I have mainly not expressed despite many occasions to do so, so I would now greatly appreciate it if you took a moment to consider things from my perspective as someone building a motor controller for commercial purposes.


Fire away.


> First off, I think it is more than just a tad ironic to complain about how much motor controllers cost on the one hand _and_ that there are no "good DIY designs" out there on the other! Doesn't that tell you right there that _it really isn't very easy to design one of these things in the first place?_


I agree with that point. Let's remember that I was answering the question of the point of this thread. It isn't easy to design a PWM controller that's effective and reliable. And once you've done it, then charging a decent amount for your efforts is warranted.

My true complaint is to say that PWM controllers are the only useful type of controller. To me that creates a predicament that reliable, cheap, and DIY is impossible to accomplish. But a rectactor, or possibly a BatPack type setup can in fact meet those requirements. It ain't perfect, but it's much better and cheaper and more reliable than nothing.



> I've been working 7 days a week on a controller design since last September and Qer, who is writing the firmware, joined the effort not too long afterwards. Both of us are working now in exchange for a portion of the profits later. In other words, pretty much for free at this point in time. I have been receiving a modest stipend of $2000 per month to, literally, pay the bills (and which will be deducted from my future profit share, btw) but that rather pales in contrast to what I could have billed for my time thus far (at the going rate of $50-$100 per hour, somewhere north of $50k at least).


Tough work for future profit. I understand. I agree. Unfortunately there are some of us who won't be able to afford such a controller. Or have to show a price sensitive proof of concept to "She who must be obeyed." in order to get funding for that perfect controller.

BTW I do once again want to offer my appreciation for the discussions that you've offered over the last few months. I've learned more about driving high power electronics here than anywhere else.



> Some people - especially on that ecomodders forum - expect folks like me to give away that effort for *free*. Ain't gonna happen. Oh, and it's not because of a few lost sales from DIY'ers that concerns us, mind you, it's from others outright ripping us off. And before anyone mentions the "creative commons" type of IP licenses (like GPL) as a means to protect ourselves from that sort of theft, do keep in mind that China is not exactly known for respecting the intellectual property of others...


Note that I stated that I fully expect Paul Holmes' controller to go boom down the line. I know full well that a solid PWM controller is much more than just throwing a handful of parts into a box.

That's the reason that I'm having this discussion which effectively dumbs down the requirements. Except, as I have learned, it really doesn't. It's just as tough to switch 24V or 36V at 100 Hz or less as it is to switch 144V or 156V @ 16 KHz.

As for China, it's likely that many manufacturers there will not repect any license or patent. There are too many instances of wholesale ripoffs of product.



> One last thing... there are some people here who have a tremendous depth of knowledge that was earned through years of hard work, self-study (and even formal education). I am thinking, for example, of _major_ when it comes to motors or _Qer_ when it comes to programming (I can attest that he knows his stuff... his code is operating my controller prototype right now, and there have been *no* issues with his work). Respect that knowledge by not assuming you are entitled to its full benefit.
> 
> </rant>


No gripe from me on that. I'm a PhD in CS and a university professor. So I know where you are coming from. It's one of the reasons I have no fear of the software side of things. But the power electronics engineering is frankly scary.

ga2500ev


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## order99 (Sep 8, 2008)

ga2500ev-

Many thanks for your patience,now i've got a place to start my education! Still can't read a schematic worth a darn, but the design looks basic enough that Dad might be able to translate-he was an Electrician for awhile. The Rectactor design sounds like something I might actually understand(eventually...), less like a TV set and more like a Crystal Radio Kit...

...and if i'm wrong about the 'might actually understand' part, i'll be failing on a superlight, test-bed Junkmobile, so it's all good! 

Good luck on the Batpack-the way you describe it constantly switching on the strongest cells, it sounds like even Lithiums would stay in balance. Off to pester the EVDL awhile...


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## ga2500ev (Apr 20, 2008)

I found the Lee Hart article that has the 96V rectactor and more explanation:

http://www.repp.org/discussion/ev/200110/msg00839.html

ga2500ev


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## order99 (Sep 8, 2008)

Thanks again. And here's that 48V I was looking for:

http://img169.imageshack.us/img169/6408/pg6mn4.jpg

Oh wait, I forgot we can upload!


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## ga2500ev (Apr 20, 2008)

That's fundamentally a rectactor. It seems to have the charging circuit integrated in too. The only thing that seems to be missing is the slow resistor and its switch.

ga2500ev


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## Tesseract (Sep 27, 2008)

Technologic said:


> To assume that you would have made $50-100/hour designing such a controller is a bit silly, especially in today's marketplace. Granted in the end your R&D will be much cheaper than if a company just outsourced it, but that's namely because there's only 2 people involved, without a limited time frame.


So you think the going rate of $50-$100 per hour for contract electronic engineering design is "silly"? Hmmm... most of my clients think it's a bargain compared to hiring an engineer full time.




Technologic said:


> The problem I'm encountering seeing DC PWM controllers over $1000 is that AC motor controllers like 96v 300a Zapis etc...are the same price.


And you think that a DC motor controller should cost less than $1000 because some Italian company's AC forklift motor controller costs that much?




Technologic said:


> 3 phase AC design is a few orders of magnitude more complicated (from schematics I've seen), yet there are reliable controllers with regen out there for less than the lowest line Zillas.


And you think the Zapi controllers with regen (e.g. - the H3) are "reliable" even though a quick Google search turned up post after post from people saying their's went boom the first time they went into regen?




Technologic said:


> I think Kelly's prices are more on track, the problem is reliability I suppose with some older models being overrated.


And you think that Kelly's prices are better even though you admit that they, shall we say, "exaggerate" their advertised specs?




Technologic said:


> I actually think some of kelly's prices are too much... go figure. ...


Oops. Maybe not. So even the cheapest controllers on the planet are too expensive for you?




Technologic said:


> ... I think a $2000, 400v x 600amp 3 phase AC controller would be a better controller build option for sales volume. Such a controller would probably be leased out to a lot of major car companies to save R&D.


I have no doubt a 415.2kW* controller would sell like hotcakes if the price was a mere $2000. Since the IGBT modules alone would cost around $900 (based on our price for quantities of 100) this seems, well... I'll refrain from making a value judgement here, but I will say it is no surprise that so few companies want to deal with DIYers. 



* - (400 x 600 x 1.73)


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## Technologic (Jul 20, 2008)

Tesseract said:


> \
> 
> And you think that a DC motor controller should cost less than $1000 because some Italian company's AC forklift motor controller costs that much?


It's not as if they're the only company with similar offerings. Curtis makes several AC controllers the most expensive of which is only $1300



> And you think the Zapi controllers with regen (e.g. - the H3) are "reliable" even though a quick Google search turned up post after post from people saying their's went boom the first time they went into regen?


People break anything in a DIY setting. I'm sure someone somehow will figure out a way to break your controller eventually




> And you think that Kelly's prices are better even though you admit that they, shall we say, "exaggerate" their advertised specs?
> Oops. Maybe not. So even the cheapest controllers on the planet are too expensive for you?


My personal experiences with the chinese dictate extreme skepticism paying much for powered electronics. In a land were 52" LCD TVs were $400 2 years ago, I can't imagine there's much justification for $2000-3000 dollar OEM priced controllers.



> I have no doubt a 415.2kW* controller would sell like hotcakes if the price was a mere $2000. Since the IGBT modules alone would cost around $900 (based on our price for quantities of 100) this seems, well... I'll refrain from making a value judgement here, but I will say it is no surprise that so few companies want to deal with DIYers.


Are you not using a similar IGBT? or what? I thought that was your planned power rating scale.

At any rate for my purposes (and most on here) I think any 3 phase AC controller under $1000 if it could take 96vx200-300a would sell like hotcakes... and to every hybrid manufacturer. (20-30kw controller)

$50-100/hr is not what EE's are being paid right now with 4 year degrees. More like $25-30/hour. 
Granted I have no idea your educational background or anything. Staffing someone is always more expensive. If you are contracting your services you can always expect 2-3 times the average wage... even if you're designing adhesives.

I'm not begrudging you your earned wages... I'm merely telling you people like me, who have much experience (both good and bad) with the chinese, realize what we should be paying for things like this. I know that your average $600 kelly controller probably costs $50-150 on a boat. I'm not willing to settle for that kind of 6 times markup unless I can not locate their source myself.

It's very common for profits in china to be a set amount... for instance legally some areas can not make more than 15% profit on goods. 

I actually once located the speaker company in china that made all of JL audios frames, cones etc. as well as Sony's Pentagon subs... you'd be surprised how cheap a 12" one of those was (they had no issues cloning them and selling them).... think 3000% cheaper than MSRP. I will tell you now as well... there's no R&D in speakers (maybe 2-3 hours to design and CAD one which I can do) so the excuse they were recouping design costs is a big no.

My skepticism isn't stemming from you building a bad controller... I'm sure it will be quite good. People like me, and car manfacturers will never pay more than what I've stated here... a controller like this a car purchase manager would instantly say "ok that'll be $250" to power their civic EVs (at least this is what I've gathered from the prices Hyundai pays for parts). I'm willing to pay 4 times that price for lower volumes... I think that's fair. Granted I haven't researched IGBT prices from chinese makers themselves either. I can't imagine such a thing would be the EE's job as well.


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## Qer (May 7, 2008)

Technologic said:


> People break anything in a DIY setting. I'm sure someone somehow will figure out a way to break your controller eventually


Hm? I thought the Zilla was more or less unbreakable? I know of one Zilla actually dying, but that was also pretty severely tortured on the drag racing strip, and one that was DOA. Apart from that I don't know of anyone else. However, I haven't hang around in EV-forums for long so I could've missed it there were more problems with them so please correct me if I'm wrong.



Technologic said:


> Are you not using a similar IGBT? or what? I thought that was your planned power rating scale.


Brushed DC-controllers only need one single IGBT (unless you want more current, of course). 3-phase AC-controllers need six. That kinda jack up the price a bit...


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## Technologic (Jul 20, 2008)

Qer said:


> Hm? I thought the Zilla was more or less unbreakable? I know of one Zilla actually dying, but that was also pretty severely tortured on the drag racing strip, and one that was DOA. Apart from that I don't know of anyone else. However, I haven't hang around in EV-forums for long so I could've missed it there were more problems with them so please correct me if I'm wrong.


My car's plans will at peak HP output 18kw... I don't suspect I could burn a kelly if I tried either. One could say, people are merely abusing or not overrating their controller purchases enough.
I have no idea if Zillas have broken, for $4000 if they broke it's be a crime against humanity though.


> Brushed DC-controllers only need one single IGBT (unless you want more current, of course). 3-phase AC-controllers need six. That kinda jack up the price a bit...


I'm sure it does. Though IGBTs, and large IGBTs are not the only way to build things.


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## Qer (May 7, 2008)

Technologic said:


> My car's plans will at peak HP output 18kw... I don't suspect I could burn a kelly if I tried either. One could say, people are merely abusing or not overrating their controller purchases enough.


Ehm. Some of the controllers (no matter brand) has died at comparatively low power outputs. It's not the power, or the current, that kills them...



Technologic said:


> I have no idea if Zillas have broken, for $4000 if they broke it's be a crime against humanity though.


You're exaggerating. Before Otmar shut down the business I was planning to buy a Zilla Z1K-LV and back then it was $1975. Sure, it's definitely not cheap, but it's pretty far from the $4000 you claim.

Our controller will end up with a price in about the same range and since I've now seen the inside, so to speak, I fully understand why. Quality cost.



Technologic said:


> I'm sure it does. Though IGBTs, and large IGBTs are not the only way to build things.


MOSFET's don't come much cheaper.


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## Technologic (Jul 20, 2008)

Qer said:


> Ehm. Some of the controllers (no matter brand) has died at comparatively low power outputs. It's not the power, or the current, that kills them...
> 
> 
> MOSFET's don't come much cheaper.


Not sure what else could kill them outside of stray inductance or something (which in theory could be remedied with a few $2 parts).

Depends where are you sourcing the MOSFETs?

At any rate I think your price is fair enough considering. There is just a stark lack of AC controllers, and it's the only reason I'd be willing to pay much for a controller.


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## Qer (May 7, 2008)

Technologic said:


> Not sure what else could kill them outside of stray inductance or something (which in theory could be remedied with a few $2 parts).


Uhm. Right...

Tell you what. Since you know so much about the stuff, why don't you start manufacture controllers? If you can roll them out at the prices you claim, the market will be yours in a jiffy!


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## Technologic (Jul 20, 2008)

Qer said:


> Uhm. Right...
> 
> Tell you what. Since you know so much about the stuff, why don't you start manufacture controllers? If you can roll them out at the prices you claim, the market will be yours in a jiffy!


I'm not claiming anything about my personal abilities to design one.

if I had a schematic at all for a large format DC controller, I could probably figure out how much it'd cost though at it's cheapest.

I was explaining that as a customer and person who's had some experience dealing with chinese PCIs I don't think most companies or people in general will want to pay that kind of money for such a controller.

Sure you can sell at otmar's sales volume or a bit higher, but that's not what I reckon you want. 

*shrugs* and from a personal perspective I'd rather heat sink a Curtis to hell and back in an AC system to make sure it survives... DC just has so many inherent problems to me I'm unwilling to pay much for it (and it's never used in manufactured cars)


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## reg (Sep 12, 2009)

I'm just getting started with the concepts here. 

My application requires some initial slow speed control. I was thinking of switching in a low power controller to get started, then removing it once i've switched in more batteries. 

Switching contactors might work fine, but I've been looking into ideal diodes too. I see the following IC's (and relatives) might be worth looking into:

LTC4352 - Low Voltage Ideal Diode Controller with Monitoring
LTC4414 - 36V, Low Loss PowerPath Controller for Large PFETs
LTC2952 - Push Button PowerPath Controller with Supervisor

I'm not sure if I understand why the Batpack has to switch as fast as it does? I imagine I'll be charging all the batteries independantly anyways, so I was thinking I could switch the freshest batteries in whenever I wanted, even manually.


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