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What is a "Gid"?

Posted: Tue Feb 07, 2012 11:40 pm
by Ingineer
I don't have one of Gary's meters, but I'm reasonably sure that what Gary found on the CAN bus is not the SOC, it's watt-hours / 80. So if you multiply "Gids" * 80, you get the true capacity in watt hours, or you can multiply by .08 and get kWh.

I typically see a full charge stop at 94-95% true SOC. My last charge to "100%" was actually to 94.591% SOC, and 22240 watt-hours, which is 271 "Gids".

Just so you guys all know!

-Phil

Re: What is a "Gid"?

Posted: Wed Feb 08, 2012 12:06 am
by TonyWilliams
You got it !

Re: What is a "Gid"?

Posted: Wed Feb 08, 2012 12:08 am
by TomT
Why don't you guys compare notes... That way we all win!
Ingineer wrote:I don't have one of Gary's meters, but I'm reasonably sure that what Gary found on the CAN bus is not the SOC, it's watt-hours / 80.

Re: What is a "Gid"?

Posted: Wed Feb 08, 2012 12:36 am
by TonyWilliams
TomT wrote:Why don't you guys compare notes... That way we all win!
Ingineer wrote:I don't have one of Gary's meters, but I'm reasonably sure that what Gary found on the CAN bus is not the SOC, it's watt-hours / 80.


Ya, wouldn't that be awesome!

Phil, why do we not measure these 22.5kWh (281.25 Gid) when our typical dash miles/kWh divided by miles driven (when driven all the way from 281 Gid to 1 or 2 Gid)?

More typical is 18-21.5-ish kWh, depending largely on temperature. For example, I drive 100 miles, and average 4.8 miles/kWh, that infers 100/4.8=20.8kWh.

Also, for the sake of continuity, might I suggest that we simply consider SOC that we have access to. I recognize the battery has more, but I think of it as fuel sloshing around in the gas tank that the fuel pump can't access. Yes, there's a little more in there, but we've already burnt 100% of the usable and available energy.

Finally, a request. Can we please bump up the cell voltage from 4.1v to 4.2v ?

Re: What is a "Gid"?

Posted: Wed Feb 08, 2012 1:02 am
by Ingineer
I don't yet have an answer for that, but I trust the battery ECU's calculations of SOC and watt-hours much better than the crappy software in the combination meter. There's many possibilities for error. One obvious one is other systems using energy in the car.

-Phil

Re: What is a "Gid"?

Posted: Wed Feb 08, 2012 5:05 am
by TickTock
Ingineer wrote:I don't have one of Gary's meters, but I'm reasonably sure that what Gary found on the CAN bus is not the SOC, it's watt-hours / 80. So if you multiply "Gids" * 80, you get the true capacity in watt hours, or you can multiply by .08 and get kWh.

I typically see a full charge stop at 94-95% true SOC. My last charge to "100%" was actually to 94.591% SOC, and 22240 watt-hours, which is 271 "Gids".

Just so you guys all know!

-Phil


I can confirm that. I got 79.0 average kw/gid on one charge and 83.4 on another as measured going into the battery. Below is a plot of the energy per gid for two separate 100% charges. There is a lot of noise but the average value matches yours. Was the 22240 from the wall or into the battery?

Image

Re: What is a "Gid"?

Posted: Wed Feb 08, 2012 5:16 am
by Herm
a wh meter would give you consistent range estimates (all else being equal) and be linear, but apparently the GID meter is not linear.. IIRC

Re: What is a "Gid"?

Posted: Wed Feb 08, 2012 5:56 am
by TickTock
There is some non-linearity, true, but it's still a lot better than the 12 bars on the dash. The graph below shows the non-linearity better, I think. I plotted the energy into the battery versus time and gids vs time during the same 100% charge. You can see that the energy into the battery is a very linear constant rate (as expected), but the gids do vary a little - particularly at the low end. Note there are two separate Y axis (charge in kwh on right and gids on the left), so don't read anything into the separation at the end of the charge cycle.

Image

Re: What is a "Gid"?

Posted: Wed Feb 08, 2012 9:24 am
by TonyWilliams
Has anybody yet found the battery temperature raw data?

Re: What is a "Gid"?

Posted: Wed Feb 08, 2012 11:20 am
by chris1howell
I think the interesting question here for Ingineer is how did you know your SOC was 94.591%...?

My last charge to "100%" was actually to 94.591% SOC


I typically see a full charge stop at 94-95% true SOC