[Oeva-list] Last nights meeting.

[Graunke, Gary]

The presentation is on my website (you can't see it from the home page but can download it directly):  http://ev.whitecape.org/EV101.ppt  .

I don't know if the Tesla has user adjustable regenerative braking-only that it was turned up quite a bit. Except for the freeway offramp, I could use regen braking to do most of the work.

The AC/BLDC motors will last an extremely long time-perhaps 1 million miles (twice as long as some diesels). If they are overheating, regen may produce more heat. But a properly cooled motor will not suffer just because it is used as a generator.

On the other hand, on a DC motor, the brushes will wear out faster. They should be advanced in timing to be a motor and retarded to be a generator. Unless you move the brushes (that's asking for trouble), they usually end up top-dead-center as a compromise and thus wear out faster.

Each battery chemistry will have it's own parameters. For laptops connected to the wall, 40% SOC is optimal for longest battery life. If you are not connected, it may be well to go to 75% to give some self-discharge time. You don't want them to run all the way down (NiCD batteries can do this, but no others). This sounds reasonable-maybe erroring on the side of conservative.

I suspect that the 110V charge reduces the charge current to the point that the shunts can equalize them without burning up. Ideally, the 240V charger should also do this with appropriate feedback from the BMS, but this seems to be lacking. If you have let them sit for a while without charging, an equalization charge at 110 would be a good idea the first time. Then you can resume normal operation.

Your batteries are really good batteries-they set the electric record for the race to the top of Pike's Peak some years ago.

Gary



________________________________
From: oeva-list-bounces at oeva.org [mailto:oeva-list-bounces at oeva.org] On Behalf Of Ray Blackburn
Sent: Friday, March 13, 2009 12:41 PM
To: oeva-list at oeva.org
Subject: [Oeva-list] Last nights meeting.

That was a very interesting presentation from Gary Graunke at last nights meeting.  It helped me alot as I don't know much about EV's and how they work.

I have some questions.

I was wanting to recap some of the info.  Is there a website that might point out the basics in the slide presentation?

The Tesla you drove, did it have adjustable regen braking?  Is adjustable regen braking advisable on AC conversions?  Perhaps the Tesla regen braking is tied to how much brake is applied if it does not have an adjustment?

If you get 10% extended range out of regen braking does it take 10% off your engine life?  What takes place in the AC electric motor to make it go from producing power to the wheels to producing power to the pack during the regen braking process?  Sorry if you covered this and I missed it.  A few members needed to pay dues during your presentation.


Comments from the people who developed and built my car about lithium batteries.  Do they sound right?

If not using the car, the batteries should be stored at 75%.

The batteries have 1,500 cycles if discharched 100 miles.  2,500 cycles if discharched 50 miles on average.

Do not leave the batteries at the 40% level for more than a day..

When charging at 220  the Battery Management Screen should be charging cells with in  2 thousandths Volts.  If the cells are not charging within 2 thousandths and are 10 thousandths apart the car should be unplugged and charged with 110.

If the car is being stored and the power switches shut off the batteries can completely freeze and it will not harm them.  For use after freezing they recommend waiting while the battery warmers bring the batteries up to operating tempature.

The voltage on any cell should not go below 2.5 volts.

When the BMS screen reads 0 miles left for range I still have approx. 20% of the pack left.

The part of the presentation about 33 KWh = 1 gal of gas was interesting as I calculate I am getting 100 miles to the gallon with my 35 KWh pack.  Also that regen breaking does take more life off the engine.  I went to Mr Kraunke's website http://ev.whitecape.org/ and saw how he deshelled those Dewalt batteries and preped them for use in the Insight EV, that was pretty neat.  Thanks again Mr Kraunke.
Ray Blackburn OEVA Treasurer.

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