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#21
05-30-2012, 02:46 PM
 MN Driver Senior Member Join Date: Sep 2009 Posts: 823
Re: High battery voltage and controller longevity

Quote:
 Originally Posted by Tesseract 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.
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.

Last edited by MN Driver; 05-30-2012 at 02:49 PM.
#22
05-30-2012, 03:55 PM
 Tesseract Senior Member Join Date: Sep 2008 Location: Tampa, FL USA Posts: 2,642
Re: High battery voltage and controller longevity

Quote:
 Originally Posted by MN Driver ...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.
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Last edited by Tesseract; 05-30-2012 at 03:56 PM. Reason: oops
#23
05-30-2012, 04:01 PM
 jehan12413 Senior Member Join Date: Feb 2010 Posts: 126
Re: High battery voltage and controller longevity

Quote:
 Originally Posted by Ziggythewiz 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?
#24
05-30-2012, 09:52 PM
 ruckus Senior Member Join Date: Apr 2009 Posts: 638
Re: High battery voltage and controller longevity

Quote:
 Originally Posted by Tesseract 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..
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#25
05-31-2012, 05:54 AM
 Tesseract Senior Member Join Date: Sep 2008 Location: Tampa, FL USA Posts: 2,642
Re: High battery voltage and controller longevity

Quote:
 Originally Posted by ruckus 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.
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#26
05-31-2012, 01:34 PM
 MN Driver Senior Member Join Date: Sep 2009 Posts: 823
Re: High battery voltage and controller longevity

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.
#27
05-31-2012, 07:07 PM
 ruckus Senior Member Join Date: Apr 2009 Posts: 638
Re: High battery voltage and controller longevity

Quote:
 Originally Posted by Tesseract 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
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Last edited by ruckus; 05-31-2012 at 07:31 PM.
#28
05-31-2012, 07:45 PM
 somanywelps Senior Member Join Date: Jan 2012 Posts: 431
Re: High battery voltage and controller longevity

Quote:
 Originally Posted by ruckus 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.
#29
05-31-2012, 10:58 PM
 ruckus Senior Member Join Date: Apr 2009 Posts: 638
Re: High battery voltage and controller longevity

Quote:
 Originally Posted by somanywelps 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..
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#30
06-01-2012, 04:56 PM
 DavidDymaxion Senior Member Join Date: Dec 2008 Posts: 1,302
Re: High battery voltage and controller longevity

· Maximum Battery Current at 200V: 1900 Amps
· Maximum Battery Current at 300V: 1770 Amps
· Maximum Battery Current at 400V: 1600 Amps
Quote:
 Originally Posted by ruckus 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..
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