# High battery voltage and controller longevity



## Tesseract (Sep 27, 2008)

Well, it's generally true that the closer you run anything to its limits the shorter its lifespan will be. More specifically, switching losses go up with voltage (and current and frequency) so the controller will run hotter at a higher voltage, all else being equal.

Thus, the maximum current is reduced by 100A if the battery pack voltage is above 310V in the Soliton1 and Soliton Jr controllers. If you don't intend to run your Soliton Jr above 500A then this won't affect you, otherwise you might want to reduce the number of series cells to 90 or less.


----------



## sheik480 (May 8, 2012)

Tesseract said:


> Well, it's generally true that the closer you run anything to its limits the shorter its lifespan will be. More specifically, switching losses go up with voltage (and current and frequency) so the controller will run hotter at a higher voltage, all else being equal.
> 
> Thus, the maximum current is reduced by 100A if the battery pack voltage is above 310V in the Soliton1 and Soliton Jr controllers. If you don't intend to run your Soliton Jr above 500A then this won't affect you, otherwise you might want to reduce the number of series cells to 90 or less.


This is exactly what I would not have expected. I imagine it wouldn't be a _problem_ with sufficient cooling, but it's good to know that not only amps make heat. I should have figured that stress goes up with power, however that power rises.


----------



## sheik480 (May 8, 2012)

If you feel so inclined, could you roughly estimate how much hotter it would run compared to a 60s system?


----------



## subcooledheatpump (Mar 5, 2012)

You might also be interested to know, the elevation of the controller also affects it's lifetime, especially with respect to high voltages. 

numerous studies have concluded that electronics are exposed to more cosmic radiation at high altitudes, and that high voltage electronics are affected the most. So it may be an important factor if you are running in high elevations. 

When switching, the switching electronics inevitably switch some parasitic inductance. Switching off inductance creates a high voltage spike. Controllers have built in diodes (or the body diode of a MOSFET) which serve to shunt the reverse voltage spike. However, the higher the bus voltage is (or bus current), the more the diodes lose in terms of conduction losses, since they are not perfect conductors. So, more turn off voltage means more turn off current in the diode, thus more losses. So losses estimate..... P=I2R... though only in respect to the switching frequency and pulse width since the current is being switched.. higher frequencies means more losses.


----------



## sheik480 (May 8, 2012)

subcooledheatpump said:


> You might also be interested to know, the elevation of the controller also affects it's lifetime, especially with respect to high voltages.
> 
> numerous studies have concluded that electronics are exposed to more cosmic radiation at high altitudes, and that high voltage electronics are affected the most. So it may be an important factor if you are running in high elevations.
> 
> When switching, the switching electronics inevitably switch some parasitic inductance. Switching off inductance creates a high voltage spike. Controllers have built in diodes (or the body diode of a MOSFET) which serve to shunt the reverse voltage spike. However, the higher the bus voltage is (or bus current), the more the diodes lose in terms of conduction losses, since they are not perfect conductors. So, more turn off voltage means more turn off current in the diode, thus more losses. So losses estimate..... P=I2R... though only in respect to the switching frequency and pulse width since the current is being switched.. higher frequencies means more losses.


The connection with high altitude is quite interesting. I spend almost all of my time below 1500 feet, so that would not be a problem, but I imagine it is a good factor to remember.


----------



## jeremyjs (Sep 22, 2010)

subcooledheatpump said:


> You might also be interested to know, the elevation of the controller also affects it's lifetime, especially with respect to high voltages.
> 
> numerous studies have concluded that electronics are exposed to more cosmic radiation at high altitudes, and that high voltage electronics are affected the most. So it may be an important factor if you are running in high elevations.



interesting. I wonder if it's noticeable? I mean to the average electronics user. If being at 5000 feet reduces the average piece of electronics lifespan by 1% no one but a statistician will notice, but if it's 10% it starts to make a noticeable difference.


----------



## Ziggythewiz (May 16, 2010)

I would think the biggest effect of high altitude would be reduced cooling due to thinner air. The main effect of cosmic radiation is typically bit flips in system memory which can cause system instability and BSODs.


----------



## sheik480 (May 8, 2012)

Ziggythewiz said:


> I would think the biggest effect of high altitude would be reduced cooling due to thinner air. The main effect of cosmic radiation is typically bit flips in system memory which can cause system instability and BSODs.


Whoops, there goes your throttle calibration.


----------



## Tesseract (Sep 27, 2008)

sheik480 said:


> If you feel so inclined, could you roughly estimate how much hotter it would run compared to a 60s system?


I can calculate the losses out exactly for a given operating point (input voltage, duty cycle, switching frequency, output current) but EV motor controllers aren't operated at a fixed operating point.

Assuming an output current of 400A and a switching frequency of 8kHz:

If you adjust the duty cycle so that the output power is the same then the losses are 3% higher at 300V vs. 200V.

If you keep duty cycle the same so that output power goes up with input voltage then the losses are 24% higher at 300V than at 200V.

Overall controller efficiency is at least 98% in all cases above as the total losses range from 550W to 700W while the output power ranges from 40kW to 60kW.


----------



## Batterypoweredtoad (Feb 5, 2008)

Tesseract said:


> Well, it's generally true that the closer you run anything to its limits the shorter its lifespan will be. More specifically, switching losses go up with voltage (and current and frequency) so the controller will run hotter at a higher voltage, all else being equal.
> 
> Thus, the maximum current is reduced by 100A if the battery pack voltage is above 310V in the Soliton1 and Soliton Jr controllers. If you don't intend to run your Soliton Jr above 500A then this won't affect you, otherwise you might want to reduce the number of series cells to 90 or less.


Is the peak current limit reduction due to high pack voltage a calculation based on pack voltage at any given moment or based on pack voltage at turn on?


----------



## Tesseract (Sep 27, 2008)

Batterypoweredtoad said:


> Is the peak current limit reduction due to high pack voltage a calculation based on pack voltage at any given moment or based on pack voltage at turn on?


Pack voltage is periodically sampled and max allowed motor current selected at each interval.


----------



## Batterypoweredtoad (Feb 5, 2008)

Is the pack voltage sample frequency frequent enough that the amount of sag you typically get during a high amp pull would be enough to bump the limit back up during that particular pull? Basically if you have a resting pack voltage of more than 310V are you always in the 100A reduction or just when it really doesn't matter. Sorry to bug you for specifics, but all my pack brainstorms have been over 310V resting and I am wondering if I should change that.


----------



## Tesseract (Sep 27, 2008)

Batterypoweredtoad said:


> Is the pack voltage sample frequency frequent enough that the amount of sag you typically get during a high amp pull would be enough to bump the limit back up during that particular pull? Basically if you have a resting pack voltage of more than 310V are you always in the 100A reduction or just when it really doesn't matter. Sorry to bug you for specifics, but all my pack brainstorms have been over 310V resting and I am wondering if I should change that.


Pack voltage is sampled at 1500Hz, IIRC. It's been 4 years since Qer and I set that and I have not had to tweak it since.

If throttle is at maximum and motor current limit is set to 1000A then output current will suddenly jump to 1000A as pack voltage falls below 310V.

I have to say I am puzzled by this repeated focus on this particular function in our controllers. Zilla uses a similar, though even more Draconian approach, limiting max allowed battery current in steps starting at, IIRC, 200V. It's the price you have to pay for the controller to work over so wide a voltage range.


----------



## Batterypoweredtoad (Feb 5, 2008)

I think it's because of our natural tendency to mourn losing what we never had or used. Even though most people rarely use it they still brag about 1000amps. If it were constant it is a 10-17% power cut so it isn't insignificant, but it sounds to me like it would only be a true power cut in very very few situations. You would have to build a 100s pack of very very stiff cells to not sag below 310 volts under any decent acceleration. BTW-What the Zilla does is a non factor in any of my considerations. You guys have caused most people to leave that world behind.


----------



## subcooledheatpump (Mar 5, 2012)

For those interested in the cosmic ray/altitude affects on controllers 

http://www2.iee.or.jp/ver2/honbu/14-magazine/log/2010/2010pdf-c/2010_06c_04.pdf

It doesn't really tell you about the altitude, but it does show how the switching devices (IGBTs) stand up to high voltage while they are being irradiated


----------



## Ziggythewiz (May 16, 2010)

Interesting, but I don't understand the link between the title and the results. It seems voltage is related to failure rate, but I don't see the connection to radiation.


----------



## subcooledheatpump (Mar 5, 2012)

Basically, the higher the altitude the more exposed to cosmic radiation any piece of equipment is, thus the operating voltage must be lowered. I don't completely understand the connection myself, but I know that cosmc rays and high voltage both cause failures. So you'll have to give in somewhere to protect your equipment. IE if you want high voltage, you must lower your altitude. If you want high altitude, you must lower your voltage. I only posted because I thought it would be revelant to the intrest of the OP, that is operating at high voltages and how it affects the life of the machine. It's okay to operate at high voltages, as long as you aren't taking your EV to a mountain area


----------



## sheik480 (May 8, 2012)

My question has been answered excellently and beyond my expectations. Receiving a response straight from the source has been an honor and provided me with information that I greatly trust, especially considering it wasn't a sales pitch. I don't think I would allow amperage above 500 as, with the engine I would like to use, that would exceed the torque the original engine produced, and allows for driving characteristics similar to the pre-conversion vehicle. Not having to slip the clutch will be nice.


----------



## Batterypoweredtoad (Feb 5, 2008)

sheik480 said:


> My question has been answered excellently and beyond my expectations. Receiving a response straight from the source has been an honor and provided me with information that I greatly trust, especially considering it wasn't a sales pitch.


Hell it goes beyond just not being a sales pitch-Tess was on here the other day giving technical support for a Zilla owner.


----------



## MN Driver (Sep 29, 2009)

Tesseract said:


> I can calculate the losses out exactly for a given operating point (input voltage, duty cycle, switching frequency, output current) but EV motor controllers aren't operated at a fixed operating point.
> 
> Assuming an output current of 400A and a switching frequency of 8kHz:
> 
> ...


I know you probably don't want to dig into this too much, send me a PM if this is getting too application specific but I'm looking to run around 96 cells because I'm looking to get fairly close to 20kwh and the 90Ah and 100Ah cells are too large for a 20kwh capacity and to maintain voltage for peak performance with a Kostov 220v(nominal) motor which means I'm looking at 60Ah cells(hoping Sinopoly makes it to the US because their 60Ah B-size cell is light and relatively small).

I'm looking to be pulling 10kw with a very light and aerodynamic car while cruising most of the time. If I'm at 300v(rounding the number for easy math) pulling 10kw which is about 33.3 amps from the batteries, and the motor is cruising at Kostov's high RPM and around 150v(66.6 amps), I'm trying to get a decent guess on efficiency losses, mostly because I'm trying to build an extremely efficient car that is 1900 pounds pre-conversion weight with excellent aerodynamics. I went with Kostov because their efficiency with their higher voltage Kostov 9 looks great and my only other option would be to run a lower voltage system with 100Ah cells using an Impulse 9 as a compromise motor but it looks on paper like that is a lower efficiency option and I'd lose highway passing performance(and acceleration in general unless I upped to a Sol 1 but that would be overkill for the car and to 100Ah Chinese prismatic batteries), and put myself at a disadvantage to the stock transmission gearing of the car.

It sounds like the efficiency loss at cruising would be minimal but I'd still like to quantify it in my most common scenario. I've had people PM me from the 1st Gen Honda Insight forums telling me to AC50 but I'm seeing much higher losses through the Curtis AC controller itself than I would through both an interpoled series DC motor and controller together.


----------



## Tesseract (Sep 27, 2008)

MN Driver said:


> ...I'm looking to be pulling 10kw ...


You didn't give me a motor current, and efficiency depends primarily on that. If it's, say, 100A then efficiency will be right at 99%.

EDIT - ah, you did. Ok. 99.1% at the specified 66A/150V on the output.


----------



## jehan12413 (Feb 4, 2010)

Ziggythewiz said:


> I would think the biggest effect of high altitude would be reduced cooling due to thinner air. The main effect of cosmic radiation is typically bit flips in system memory which can cause system instability and BSODs.


 I have always wondered about the effect of radiation on electronics. Since I fly for a living I decided to measure it a while back and what I discovered was that at sea level background radiation averages 5-8 counts per min. At 35,000 feet it's 50-60 CPM but doesn't seem to increase significantly until above about 15,000 feet. Another thing I have noticed is that since I switched to smart phones I have had numerous problems. In fact I have gone through 2 iphones in the last 10 months (both started having issues during high sunspot activity). Coincidence?


----------



## ruckus (Apr 15, 2009)

Tesseract said:


> I have to say I am puzzled by this repeated focus on this particular function in our controllers. Zilla uses a similar, though even more Draconian approach, limiting max allowed battery current in steps starting at, IIRC, 200V. It's the price you have to pay for the controller to work over so wide a voltage range.


I think the interest is generated because this is one of those features not mentioned in the owners manual (at least not that I have read as a Zilla user).

It is easily explained as max watts is max watts. If you raise voltage the amperage must suffer. Heat is heat is heat.

Raising voltage is kind of a "free lunch", but as we all know, lunch is never free..


----------



## Tesseract (Sep 27, 2008)

ruckus said:


> I think the interest is generated because this is one of those features not mentioned in the owners manual (at least not that I have read as a Zilla user).....


There is a brief description of the maximum allowed battery current vs. battery voltage on p3 of the Zilla owner's manual.

Similarly, there is a brief mention of motor current being derated above 310V on p4 of the Soliton owner's manual. 

So, neither Otmar nor I have emphasized this much. I'll try to correct that in the next revision of the manual.


----------



## MN Driver (Sep 29, 2009)

I think he was saying that it wasn't in the Zilla manual based on your quote response on how the Zilla works.

I thought it was pretty clear in the Soliton manual.


----------



## ruckus (Apr 15, 2009)

Tesseract said:


> There is a brief description of the maximum allowed battery current vs. battery voltage on p3 of the Zilla owner's manual.
> 
> Similarly, there is a brief mention of motor current being derated above 310V on p4 of the Soliton owner's manual.
> 
> So, neither Otmar nor I have emphasized this much. I'll try to correct that in the next revision of the manual.


Perhaps my Zilla manual is "out of date", but there is no mention of current cutback relative to voltage level. I can copy it and scan it in if you want, but it just isn't there. On any page.

Again, I think the reason for interest is that controllers are rated by amps, with a listed range of workable voltage. A max wattage (kw) rating would help folks to understand that regardless of voltage, they will never get more than X.

Not really an issue since the new controllers are SO powerful


----------



## somanywelps (Jan 25, 2012)

ruckus said:


> Perhaps my Zilla manual is "out of date", but there is no mention of current cutback relative to voltage level. I can copy it and scan it in if you want, but it just isn't there. On any page.
> 
> Again, I think the reason for interest is that controllers are rated by amps, with a listed range of workable voltage. A max wattage (kw) rating would help folks to understand that regardless of voltage, they will never get more than X.
> 
> Not really an issue since the new controllers are SO powerful


The derating is on the product order page at MM.


----------



## ruckus (Apr 15, 2009)

somanywelps said:


> The derating is on the product order page at MM.


Ahh, that explains it. I have the manual for an ancient "by EV Components" Zilla.

Anybody remember them?

Didn't think so. History is so unkind..


----------



## DavidDymaxion (Dec 1, 2008)

· Maximum Battery Current at 200V: 1900 Amps
· Maximum Battery Current at 300V: 1770 Amps
· Maximum Battery Current at 400V: 1600 Amps


ruckus said:


> Ahh, that explains it. I have the manual for an ancient "by EV Components" Zilla.
> 
> Anybody remember them?
> 
> Didn't think so. History is so unkind..


----------



## EVfun (Mar 14, 2010)

ruckus said:


> Ahh, that explains it. I have the manual for an ancient "by EV Components" Zilla.
> 
> Anybody remember them?
> 
> Didn't think so. History is so unkind..


That is one rare, infamous, case. The Zilla inside is the same though. Both of my Zilla controllers have "by Cafe Electric" cases.


----------



## ruckus (Apr 15, 2009)

Yeah, I wonder how many went out with that stamp. Very few. We were extremely lucky to be at the top of the list..


----------

