Tim Jodice
Posts: 45
Joined: Fri Oct 25, 2013 2:40 am
Location: Amherst, NH

Lower battery capacity without less range

Fri Nov 06, 2015 6:23 am

Still Quite happy with my car as i talked about in http://www.myfocuselectric.com/forum/vi ... 9&start=10. I have not measured capacity in awhile and with winter approaching I decided to do it this week. Every day I measured it it came up with 18.1Kwh available, last year it showed 19.5. That said I still get to work with the same margin driving and heating/cooling as I always have. It shows that to do everything it did before takes less power. That would make me think the battery is as capable as it has always been but what measures power consumption is out of calibration. What i have read here most show about 19Kwh available. Has anyone seen this? Does anyone know or have a theory what caused this?

NightHawk
Posts: 535
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Location: Southern CA

Re: Lower battery capacity without less range

Fri Nov 06, 2015 12:48 pm

How are you measuring battery capacity?
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Tim Jodice
Posts: 45
Joined: Fri Oct 25, 2013 2:40 am
Location: Amherst, NH

Re: Lower battery capacity without less range

Sat Nov 07, 2015 8:34 am

I reset the trip odometer and at the end of my commute I divide the kwh used by the percent of capacity used. Example 17kwh used divided by .94 equals about.18.1. The few times I run it down to 1-2% left it works out as I expected. That said it is showing me about a 7% loss of capacity and at the end of my commute that works out to be about 3/4 of a mile so a 10 degree drop in temperature could bring it down that much. Basically negligible. I am all ears!

WattsUp
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Location: SF Bay Area, CA

Re: Lower battery capacity without less range

Sat Nov 07, 2015 4:25 pm

Tim Jodice wrote:... it is showing me about a 7% loss of capacity and at the end of my commute that works out to be about 3/4 of a mile ... Basically negligible.
Not sure I understand what you're saying, 7% capacity represents way more than just 3/4 mile.

7% of 18-19 kWh (typical capacity) is about 1200 Wh.

At 250 Wh/mi (typical), that would represent about 5 miles.
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Tim Jodice
Posts: 45
Joined: Fri Oct 25, 2013 2:40 am
Location: Amherst, NH

Re: Lower battery capacity without less range

Sat Nov 07, 2015 8:01 pm

WattsUp wrote:
Tim Jodice wrote:... it is showing me about a 7% loss of capacity and at the end of my commute that works out to be about 3/4 of a mile ... Basically negligible.
Not sure I understand what you're saying, 7% capacity represents way more than just 3/4 mile.

7% of 18-19 kWh (typical capacity) is about 1200 Wh.

At 250 Wh/mi (typical), that would represent about 5 miles.
That's right when you are looking at a full charged battery. I am referring to when I am at the end of my commute. 7% of what is remaining is only 240 Wh. I see 240-250 Wh/mi doing 50/50 city/highway. my commute is 10/90 city/highway I am usually seeing 280-290 Wh/mi spring summer and fall, Winter is 320 wh/mi. Obviously I'm not doing a good job describing this. I know there are many ways to measure power the way I described is the only way I have ever done it. Maybe the way i am doing it is not accurate measuring available power from an absolute value but there is a difference in what it displayed without a reduction in range. It is showing less power available and it is showing that it takes less power to do the same thing. Lastly your estimate of 1200wh is spot on, it used to show about 19.5Kwh now it shows no more than 18.1-.2

WattsUp
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Location: SF Bay Area, CA

Re: Lower battery capacity without less range

Sat Nov 07, 2015 11:08 pm

Tim Jodice wrote:Lastly your estimate of 1200wh is spot on, it used to show about 19.5Kwh now it shows no more than 18.1-.2
Yeah, on a full charge (of 19.5 kWh) you used to be able to drive about 5 miles further than you can now (on 18-ish kWh).

You've apparently lost about 7% capacity, or roughly 5 miles of total range. Not a huge amount, but not exactly negligible.
2013 FFE, Platinum White, Delivered January 2013
2017 MS, Midnight Silver Metallic, Delivered February 2017
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GladeStorm
Posts: 67
Joined: Thu Nov 21, 2013 9:17 am
Location: TN

Re: Lower battery capacity without less range

Sun Nov 08, 2015 7:25 am

Although the trip meter accounts for regeneration, some tests that I did last year lead me to believe that there is an accumulative error introduced. ie the more you regenerate, the less well the trip meter correlates with the SOC. -Perhaps you are braking more efficiently these days,...
2013 Ice Storm FFE

Leo
Posts: 36
Joined: Fri Feb 08, 2013 11:36 pm

Re: Lower battery capacity without less range

Sun Nov 15, 2015 12:39 am

I am getting similar results. When the car was new i could drive back and forth to work and still be over 50%. Now i am at about 45% or less. At first i thought i could be using more power/ electricity but it is close to the same kw every time. So i am storing less electricity in the batteries. I'm at 33,000 miles 34 months old.

jmueller065
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Location: Southeastern MI
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Re: Lower battery capacity without less range

Sun Nov 15, 2015 4:23 am

I'm also at the 30k+ range on my car but it still charges to ~19.5kWh for ETE.

At the moment I'm using about 25% of the battery for my commute in (instead of 20%) but that is because its November instead of July.
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michael
Posts: 1113
Joined: Sun Sep 22, 2013 9:55 am
Location: Los Angeles, CA

Re: Lower battery capacity without less range

Sun Nov 15, 2015 9:30 am

I have found the ETE estimate right at full charge to be unreliable . In my experience is shows too high. I have more confidence in the trip meter. Do a long trip, running the battery down below 25% and add the remaining ETE to the trip meter. I find this gives a value significantly lower.

Alternatively, run the heater full blast with the windows open, see what the trip meter shows at exhaustion.
2013 FFE Returned after 3 years with 52,000 miles and battery down to 15.2 kWh
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2014 Volt 26,000 miles
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