06-15-2008, 09:46 PM
I think it's possible to improve the VOLT efficiency with a GPS and with a "Go back home" push button.
If the ride is more than 40 miles, then batteries need to be charged by the generator. If you want to go back home and improve your VOLT efficiency, then just push the "Go back home" button on the dash.
Then, the VOLT computer will know that you want to go back home. With the help of the GPS, the computer will verify the distance between the car location and your house, the traffic and the number of stop needed. With these informations, the computer will stop the gas engine exactly at the right time to get a 10% charge in the batteries when the car will arrive at home. Then the efficiency will be increased by 20% because usually, the generator keeps the SOC (state of charge) at 30% capacity.
I would like to get your opinion please.
06-15-2008, 10:22 PM
I've wondered why the GM team chose 30% to 80% SOC. Was this to improve battery life? The A123 web site seems to indicate that after 7000 cycles, 0-100% SOC each cycle, that the battery has degraded from 16kW to 13kW. This seems good enough for production. Maybe going 30%-80% improves battery life even more.
Or, maybe 30%-80% was chosen so that the battery doesn't go lower than 0% or higher than 100% SOC under extraordinary driving conditions. (i.e. climbing a mountain pass in Colorado, in which case the ICE may not be able to keep up with the power demands, or decending the auto road on Mt. Washington after plugging in at the top, in which case regen will put in about 15% SOC)
If 30%-80% was indeed chosen to handle these special situations, then maybe GPS could be used to calculate whether either situation is possible. All you would have to do is look at altitude. If you are near sea level, then it would be pretty safe to allow the battery to charge to near 100% SOC. You can't regen downhill under the ocean. Likewise, it should be possible (though not as easy) to say whether there are any mountains nearby to climb (with a car), and then let the battery maybe go lower before kicking in the generator.
My first instinct as an engineer was that using a GPS is too complicated - "Keep It Simple, Stupid". But if it means you could get 2x the range out of a given battery, or 1/2 the battery for the same range, then it seems worth a bit of complexity for the money saved! We're talking about the price of the 20 mile version, but the range of the 40 mile version.
Almost forgot - GO CELTICS
06-17-2008, 05:21 PM
I think personally that it would be better to go 30-95 and just use a dynamic braking system if you're regen braking down a hill and the batteries have reached 100%. The low end of 30% will still be needed for the long uphill accelerations as it's quite difficult to pull the heat out of the ambient air and turn it into work, but switching the motor generation to a heat sink is really easy. I suspect much of it has to do with battery life.
Question though: if you live, say, at the top of Mt. Washington, start off to work with an 80% SOC, will the car allow you to brake-generate the batteries up to 100%?
06-18-2008, 03:59 PM
If you live, say, at the top of Mt. Washington, start off to work with an 80% SOC, will the car allow you to brake-generate the batteries up to 100%?
I would assume that once the 80% SOC is reached, as you continue to coast downhill, the Volt's battery management software will probably stop the regenerative charging.
With the Volt, battery management is everything. Keeping the battery within the proper SOC will be crucial for maximum battery life.
This is just my opinion, not speaking from any experience.
06-19-2008, 03:56 PM
Ummm. I do agree with "Keep It Simple, Stupid." Just have the engine keep the SOC 30%-35% until it plug in. If the volt been driving more then 5 miles under 30%-35% SOC. The engine start to charge up to 80% SOC. I think the volt should have a setting for people who could not plug in it into 100% SOC with the engine.