# pros/cons of zilla LV versus HV w 144v?



## dtbaker (Jan 5, 2008)

I am wondering if there are any pros/cons to selecting either the HV or LV version of zilla for a 'typical' build with 120v-156v battery pack.

I know the HV version supports higher pack voltage, but that seems irrelevant for the 'average' build since you shouldn't run more than 160v thru the typical motor anyway, and lots of the average DC components are rated only up to 160v as well....

so, would using an HV unit at 144v (for instance) be any less efficient or have any problems compared to a LV unit?


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## rtz (Jul 3, 2013)

I'd say no since it appears to be just sizing the controller to the pack voltage. Also an issue of cost between the two models. But does limit future upgrade options. Different motor or bigger series pack?

I think all this harkens back more to the days of stringing together 12V Lead in series. It's kinda tough getting a "high voltage" pack of Li considering the cell voltage(3.2V?). Even using 40Ah cells. I wouldn't mind seeing a lower cost, smaller/lighter cell then the 40Ah being made available so stringing together ~100 cells wouldn't be the herculean task it is now. Or for higher voltage cells to be available.

I like these 12V cells; but I think there is some funny business going on with their power output compared to regular cells?

http://www.balqon.com/12v-40ahr-lithium-battery/ 

Just 12 of those for a 144V pack... Reminds me of the lead acid days when conversions were much more simpler. Just a few batteries needed.


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## dtbaker (Jan 5, 2008)

rtz said:


> I'd say no since it appears to be just sizing the controller to the pack voltage. Also an issue of cost between the two models.


IS there a cost difference between the LV and HV? I didn't see separate listing on the Manzanita site..... 

My question comes up simply because I am wondering if it matters which to get if pack voltage is something average like 120v, 144v, 156v. The cafe electric site indicates there is some difference in build schedule and availability, but I couldn't see any info on whether one or the other would be advisable if the pack was in the 'overlap' voltage.


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## rtz (Jul 3, 2013)

I see high/low voltage models of both the Z1k and Z2k and price differences:

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

If you will never need the higher voltage potential of the controller; it just comes down to cost and if you will ever use it or not.


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## dtbaker (Jan 5, 2008)

rtz said:


> I see high/low voltage models of both the Z1k and Z2k and price differences:
> 
> http://www.evsource.com/tls_zilla.php
> 
> If you will never need the higher voltage potential of the controller; it just comes down to cost and if you will ever use it or not.



hhhmmm, I was looking at the product page at manzanita. they don't show different pricing, but perhaps carry only the LV versions....
http://www.manzanitamicro.com/products?page=shop.browse&category_id=33

regardless, I am not seeing what the advantage is to going over 156v since the motors are rated to carry more than that anyway, and most of the other average components are only rated up to 160vDC.


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## Qer (May 7, 2008)

dtbaker said:


> regardless, I am not seeing what the advantage is to going over 156v since the motors are rated to carry more than that anyway, and most of the other average components are only rated up to 160vDC.


Lower battery current and more margin to when battery sag starts to affect top RPM.


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## dtbaker (Jan 5, 2008)

Qer said:


> Lower battery current and more margin to when battery sag starts to affect top RPM.



hhmmm, so if I set the controller to limit voltage the motor sees to some 'safe' value like 160v, but I have a battery pack much higher than that, is there a loss in efficiency as the controller clamps down on the voltage? i.e. how would this affect the actual range I would be able to get from the theoretical energy in the total pack?

I can see how this might be a nice way to use smaller capacity cells, build a high voltage pack, and the motor would see less sag with the lower battery current and the batteries would be happier with lower C demand.

But this starts looking like that extra performance gets expensive.... first with the higher cost controller, then limiting choices on chargers to the very high end.


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## dougingraham (Jul 26, 2011)

dtbaker said:


> hhmmm, so if I set the controller to limit voltage the motor sees to some 'safe' value like 160v, but I have a battery pack much higher than that, is there a loss in efficiency as the controller clamps down on the voltage? i.e. how would this affect the actual range I would be able to get from the theoretical energy in the total pack?


The only thing motor controllers can physically do is lower the output voltage. They limit and control the current and RPM by lowering the effective voltage the motor sees.

If you have a 170 volt battery and you draw 1000 amps this is 170kw out of the battery. If you have a 340 volt battery and draw 500 amps it is still 170kw out of the battery. With the motor controller set to limit the output voltage to 170 volts the motor is going to see the same current with either battery setup. There are very minor differences in efficiency but generally it favors the higher voltage setup rather than the other way around. Losses are the same on the motor side but since the currents are lower on the battery side the losses are much lower. Resistive losses are represented by the equation I^2 * R. In my car I see 0.000041 ohms per battery strap. With 50 straps this is about 0.002 ohms across my 51 cell battery. With a 100 cell battery it would be about twice this so to make it easy lets assume the 340 volt battery has 0.004 ohms of resistance in the straps and a 50 cell pack has half that. At 500 amps and 0.004 ohms the losses in the 340 volt battery loop would be 1000 watts of waste heat. At 1000 amps and 0.002 ohms in the 50 cell battery the waste heat would be 2000 watts. In this example the losses are twice as much in the lower voltage system but this calculation is just the battery strap losses. The voltage sag due to the strap resistance is going to be the same 2 volts in both packs but 2 volts in a 340 volt pack is 0.6% and in a 170 volt pack it would be 1.2% of pack voltage so there is a net gain there as well.

For overall efficiency it is almost always better to go with a higher voltage lower current setup. The above example is an extreme case and we operate at the max power settings only briefly if ever in a street car that is daily driven. The losses are still relative only not so extreme. If I was going to do my car over again today I would probably use 60AH cells instead of 100AH only more of them so I was operating at a higher pack voltage and then limit the battery current appropriately.

The high voltage Zilla is probably going to cost more and depending on exactly what they used for IGBTs could be slightly less efficient in your lower voltage application but probably not enough to worry about.


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## Qer (May 7, 2008)

The only real downside with higher pack voltage i can think of (assuming we're talking sane values here) is that most chargers used in DIY-conversions seems to be buck regulators. When the pack voltage goes up so pack voltage is higher than the line can provide that's no longer an option and thus the cost for the charger will jump.


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## dtbaker (Jan 5, 2008)

Qer said:


> The only real downside with higher pack voltage i can think of (assuming we're talking sane values here) is that most chargers used in DIY-conversions seems to be buck regulators. When the pack voltage goes up so pack voltage is higher than the line can provide that's no longer an option and thus the cost for the charger will jump.


yeah, that is a concern.... once you get over 160v nominal, the choices for chargers become very limited, and very expensive. I really believe that plain outlet 110vAC level 1 slow charge is just fine for the average sub-50 mile commuter. 

so, I am coming to the conclusion that the HV version might be worth the extra money for racing to obtain top performance knowing that it bumps up the cost of several components like charger, and dc-dc, wouldn't HURT anything to use at lower voltage but why pay extra for a feature you don't plan on using if you are building a sub-160v system?!

thanks for comments and insight!

Leaves me wondering why the zilla manuf team is clearly prioritizing building the HV version when they could sell more units to the 'average' DIYer going head-to-head with the Soliton 1 based on lowest price for a full-featured 1000amp controller.....

Next minor niggle is the industry move to HEPA over POT throttle input.... I have POT in my Swift, and yes it is touchey at first requiring gentle foot to start. The HEPA in my Miata is certainly easier to start off and smoother.... I guess that is enough to justify the slight extra expense of a HEPA system over POT throttle.


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## Qer (May 7, 2008)

dtbaker said:


> Leaves me wondering why the zilla manuf team is clearly prioritizing building the HV version when they could sell more units to the 'average' DIYer going head-to-head with the Soliton 1 based on lowest price for a full-featured 1000amp controller.....


On the other hand, if you're just doing daily errands etc with the car, why do you need 1kA?

Without the battery pack and pack voltage to back it up, the only benefit you will get from 1kA is the ability to burn rubber, blow motors and break transmissions. A controller able to dish out half of that (provided it's really capable of doing so for a reasonable time too and won't cut back annoyingly fast, ie not a cheap shoe box with crappy air cooling) will probably be more than OK for a daily commuter.

Remember, if you're having a pack voltage of 160 Volt your pack will have to deliver pretty much full motor current when you start to reach top RPM. Most cells won't like much more than 3C so to get 1kA out of a pack you need something like 350 Ah.

Now, considering most DIY builds tends to have cells on 100-160 Ah that means your top pack current will "only" be somewhere around 300-400 Amps which means that your 1kA will start to dial back already at 50 Volt or so. With a torque that requires 1kA I'd estimate that to around somewhere around 1000 RPM.

Of course, if you're converting a big VAN or Pick-up you might need the power from a 1kA controller, but then you'll need the batteries for it too...


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## tomofreno (Mar 3, 2009)

dtbaker said:


> I really believe that plain outlet 110vAC level 1 slow charge is just fine for the average sub-50 mile commuter.


I agree if all you use it for is commuting, but if it is your daily driver, and you like to sometimes go places in the evening, and/or drive out further distances on weekends to do things, a higher power charger will greatly increase your options. For example, last week I drove about 50 miles to go for a hike, then drove 12 miles to an EVSE at a town 45 miles from home, charged 1 1/3 hours at about 7kW while I ate dinner at a restaurant a block away, and drove home. Last year I couldn't have done that because there was no EVSE, and even if there had been my PFC30 would have taken twice as long to charge the car. Charging at 120VAC would be ridiculous. A while back, after returning from a 60 mile round trip I got a call inviting me to dinner in 2 hours. I charged at 70A DC (at 123V pack V), and had plenty time to make the 30 mile drive to dinner, and enough charge to return home. Opens up more options.



> Leaves me wondering why the zilla manuf team is clearly prioritizing building the HV version when they could sell more units to the 'average' DIYer going head-to-head with the Soliton 1 based on lowest price for a full-featured 1000amp controller.....


 Probably because that is what has the highest customer demand.



> Next minor niggle is the industry move to HEPA over POT throttle input.... I have POT in my Swift, and yes it is touchey at first requiring gentle foot to start. The HEPA in my Miata is certainly easier to start off and smoother.... I guess that is enough to justify the slight extra expense of a HEPA system over POT throttle.


 I replaced my Curtis PB6 with a Hall Effect throttle a bit over 3 years ago because after about 9 months of use the Curtis started "jumping" in hot weather from say 30A to 150A when I pressed the pedal causing the car to either not accelerate or to suddenly lurch. No problems with the Hall throttle.


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## dtbaker (Jan 5, 2008)

Qer said:


> On the other hand, if you're just doing daily errands etc with the car, why do you need 1kA?


I don't really, but its a lot more fun. If the zilla 1k is the same price as the soliton Jr, and has all same features, why not! Second, I am about to start a larger/heavier car, but at moderate voltage, so would like 1ka to get it moving with reasonable zip.




Qer said:


> A controller able to dish out half of that (provided it's really capable of doing so for a reasonable time too and won't cut back annoyingly fast, ie not a cheap shoe box with crappy air cooling) will probably be more than OK for a daily commuter.


well, that's it in a shoebox. ;0 Yes a Curtis is cheaper, but really not practical for 20 minutes at 75mph on a slight uphill pulling a steady 200amps in the summer. Both the zilla and soliton handle that with built in fluid cooling plate where it would require an add-on to Curtis that brings the price up to the same as zilla/solitonJr with less features and lower performance.



Qer said:


> Remember, if you're having a pack voltage of 160 Volt your pack will have to deliver pretty much full motor current when you start to reach top RPM. Most cells won't like much more than 3C so to get 1kA out of a pack you need something like 350 Ah.


well.... in typical urban/suburban driving I find the capacity of the controller rarely 'maxed out', and rarely at max rpm for more than a few seconds. but it is very nice to have on occasion for a few seconds to get up to speed from a stop. Yes, this may be a strain on 'small' cells like 100ah or 130ah.... say 10C for the 100ah, but only for a few seconds at a time, which the new CALBs say they can handle without damage.


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## Semper Vivus (Apr 13, 2011)

dougingraham said:


> The only thing motor controllers can physically do is lower the output voltage. They limit and control the current and RPM by lowering the effective voltage the motor sees.
> 
> If you have a 170 volt battery and you draw 1000 amps this is 170kw out of the battery. If you have a 340 volt battery and draw 500 amps it is still 170kw out of the battery. With the motor controller set to limit the output voltage to 170 volts the motor is going to see the same current with either battery setup. There are very minor differences in efficiency but generally it favors the higher voltage setup rather than the other way around. Losses are the same on the motor side but since the currents are lower on the battery side the losses are much lower. Resistive losses are represented by the equation I^2 * R. In my car I see 0.000041 ohms per battery strap. With 50 straps this is about 0.002 ohms across my 51 cell battery. With a 100 cell battery it would be about twice this so to make it easy lets assume the 340 volt battery has 0.004 ohms of resistance in the straps and a 50 cell pack has half that. At 500 amps and 0.004 ohms the losses in the 340 volt battery loop would be 1000 watts of waste heat. At 1000 amps and 0.002 ohms in the 50 cell battery the waste heat would be 2000 watts. In this example the losses are twice as much in the lower voltage system but this calculation is just the battery strap losses. The voltage sag due to the strap resistance is going to be the same 2 volts in both packs but 2 volts in a 340 volt pack is 0.6% and in a 170 volt pack it would be 1.2% of pack voltage so there is a net gain there as well.
> 
> ...


Hello,
if you build a 50 cell pack instead of a 100, you will use cells with twice of Ah. In theory that bigger cells will have half the resistance. That would result in the same power loss (0.25 of the resistance and 2x the current compared to a higher voltage pack).
Kind regards
Tom


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## Qer (May 7, 2008)

dtbaker said:


> If the zilla 1k is the same price as the soliton Jr, and has all same features


I know I'll risk sounding like I'm trying a sales pitch here, but I simply have to correct this.

Peak current: Zilla - 1kA, Soliton Jr - 600A
Continuous current: Zilla - ~300A, Soliton Jr - ~450A
Max pack voltage: Zilla - 156V, Soliton Jr - 340V
Cooling: Zilla - water, Soliton Jr - air or water
Programming: Zilla - serial port, Soliton Jr - web interface
Idle RPM: Zilla - no, Soliton Jr - yes
Water resistant: Zilla - no, Soliton Jr - yes
Built in contactor: Zilla - no, Soliton Jr - yes
Capacitors: Zilla - ELKO, Soliton Jr - Metal film
Programmable in/out (for dashboard meters etc): Zilla - no, Soliton Jr - yes
Serial/parallel shifting: Zilla - yes, Soliton Jr - no

What is the preferred choice is of course up to you, but I object to the statement "has all same features". They do not.


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## EVfun (Mar 14, 2010)

Qer said:


> On the other hand, if you're just doing daily errands etc with the car, why do you need 1kA?
> 
> Without the battery pack and pack voltage to back it up, the only benefit you will get from 1kA is the ability to burn rubber, blow motors and break transmissions. A controller able to dish out half of that (provided it's really capable of doing so for a reasonable time too and won't cut back annoyingly fast, ie not a cheap shoe box with crappy air cooling) will probably be more than OK for a daily commuter.
> 
> Remember, if you're having a pack voltage of 160 Volt your pack will have to deliver pretty much full motor current when you start to reach top RPM. Most cells won't like much more than 3C so to get 1kA out of a pack you need something like 350 Ah.


The bottom line is that power is power. If you are going to run a low voltage pack and want... say... 100 horsepower than you simply have to move some amps. 45 cells at 2.8 vpc under max load is 126 volts. 100 horsepower is 74600 watts at 100% efficiency, so about 88000 watts input. At 126 volts that is 700 battery amps. If you cells are good for 5C then you need at least 140 amp hour cells. If you want a long range with a low voltage pack 180 amp hour cells seem to be a common choice. Many of the DC motors out there aren't comfortable much above that motor voltage anyway, though the ADC 9 inch and many of the larger motors can generally go somewhat above that. You don't want to push the voltage like the racers, that will lead to blown comms. 

If you limit yourself to a low voltage pack of up to 50 cells 600 amps will limit you to about 95 peak horsepower. If you open up to 1000 amps you can get up to 150 horsepower. 600 amps will limit you to 75 to 120 ft-lb of torque with most of the common motors used with low pack voltages (7 to 9 inch diameter 72 to 120 volt rated motors.) 1000 amps will allow you 120 to 200 ft-lb of peak torque. That probably isn't a something you should dump into a Geo Metro transaxle, but many others will take it.

I am running a very light EV so I don't need much power for fun. My pack is made of 39, 60 amp hour cells that I push for 5C (300 battery amps.) At that point they around 2.8 volts each. That's 109 volts and I wouldn't want to push a Prestolite MTC above 120 volts so I'm pretty close to the limit. I have around 36 horsepower to push around a 1200 lb. car (a 40 horsepower Bug only had 34 HP net installed and weighed 1700 lb.) I set the motor amps to 900, so I've got around 160 ft-lb of torque on demand. That is the fun, the barking tires in 2nd, or smartly leaving from a stop in 3rd. I'm running a Zilla Z1k-HV. The -HV is listed on the Manzanita Micro web site for $500 more than the -LV If you continue to where you select the options. I have my eye on going to 50 cells (if I do I'll have to limit motor voltage.)

I'd like to try a Soliton Jr. with air cooling. That case is a work of art! I may have to protect my DC>DC converter (an old Todd PC20-LV AC to DC converter) from the input ripple. I'm not sure how happy Lithium batteries are with the current ripple. Off-list I've been told that the hang time at 600 amps with air cooling is very limited (I'm running a simple thermo-syphon with the Zilla, no pump.) I'm not sure I'd be as happy with 600 peak motor amps having been spoiled with more.


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## dougingraham (Jul 26, 2011)

Semper Vivus said:


> Hello,
> if you build a 50 cell pack instead of a 100, you will use cells with twice of Ah. In theory that bigger cells will have half the resistance. That would result in the same power loss (0.25 of the resistance and 2x the current compared to a higher voltage pack).
> Kind regards
> Tom


The resistance I am referring to has nothing to do with the cells. It is the resistance of the cell interconnection straps. If you made your own straps you could double them up for the higher currents but people are generally not going to do this.

You are better off with 98 60AH cells instead of 59 100AH cells and limiting the battery current to 600 amps for the 60AH cells instead of 1000 amps for the 100AH cells With a motor like the Warp9 which can take up to 192 volts It will never see any battery sag with the high voltage 60AH cell setup but will see it every time you punch it with the 100AH cell combo.


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## Tesseract (Sep 27, 2008)

EVfun said:


> ...I'm not sure how happy Lithium batteries are with the current ripple.


Well, to be fair, no one is really sure about that, and I have actually searched IEEE Xplore for papers on this very subject. The closest I've found so far is a 2013 paper by Beh, Covic & Boys titled, "Effects of Pulse and DC Charging on Lithium Iron Phosphate (LiFePO4) Batteries". To summarize: they found no effect at all on cycle life using poorly filtered, rectified AC for charging (ie - with lots of 100/120Hz ripple).

That said, it is a bit of a stretch to assume that the woes our controllers inflict on the tiny electrolytic capacitors inside, e.g., a DC/DC converter which might be rated for all of 1-3App of ripple, will apply in a similar scale and fashion to the high Ah capacity LFP cells typically used in an EV battery pack. So unless your pack is comprised of a 1p stack of 18650 cells, reflected ripple from the controller doesn't seem to be an issue.



EVfun said:


> Off-list I've been told that the hang time at 600 amps with air cooling is very limited (I'm running a simple thermo-syphon with the Zilla, no pump.) I'm not sure I'd be as happy with 600 peak motor amps having been spoiled with more.


I suspect you would not be happy going from a 1000A controller to a 600A one. And yes, the amount of time you can get 600A from a Jr - especially if relying on just the built-in fans for cooling - is rather limited. The Jr is aimed at people with very modest performance goals *or* who are using a Kostov motor as they are wound for higher voltage/lower current. In fact, a Soliton Jr and Kostov 10" system running at ~250V will perform almost identically to a 150V system comprised of a 1000A controller and WarP-9 motor.

Finally, the Zilla is a good controller so if you already have one my opinion is that there would only be a very modest and limited benefit in "upgrading", so to speak, to a Soliton.


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