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 Post subject: Re: Battery Degradation
PostPosted: Thu Sep 19, 2013 1:42 pm 
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Joined: Sat Jun 01, 2013 3:35 pm
Posts: 61
Location: Irvine, CA
Link below to Tesla patent issued last month with the title "Electric Vehicle Battery Lifetime Optimization Operational Mode". Provides some interesting info.

http://www.faqs.org/patents/app/20130221916

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 Post subject: Re: Battery Degradation
PostPosted: Sat Apr 12, 2014 3:28 pm 
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Joined: Wed Nov 14, 2012 9:50 pm
Posts: 4115
Location: San Diego
Tesla powered Rav4 EV data:

In service November 2012. High utilization of over 2000 miles (3000km) per month. Never stored in a hot environment. The only time subject to over 100F / 38C degrees, the car was left on all day to run the battery temperature control (Rav4 EV only conditions the battery when on, while charging, or in the 15-20 minutes prior to scheduled departure of a timed preheat / precooling of the cabin).

Car is frequently cycled to low SOC%, as might be expected from high utilization. Never left parked for more than a few hours at high SOC%.

*******************

Full charge to turtle:

144.4 miles at 3.7 miles per kWh (270 watthours per mile) equals 39.0kWh

39.0 / 41.8kWh = 93.3% capacity

6.7% degradation at 20,000 miles, 9 months in service.

***************

Yesterday, drove with full charge to about 6 miles remaining:

18 months in service, 36,000 miles

94 miles driven miles plus 6 miles remaining at 2.7 miles per kWh (370 watthours per mile) equals 37.0kWh

37.0 / 41.8kWh = 88.5% capacity

11.5% degradation at 36,000 miles, 18 months in service.

****************

NOTE: these are single data point observations, and not exhaustive research.

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 Post subject: Re: Battery Degradation
PostPosted: Sat Apr 12, 2014 9:50 pm 
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Joined: Sun Mar 03, 2013 8:18 am
Posts: 208
Location: SoCal
In service date 3/4/2013, Inland Empire, 4 months a year highs over 90F, two weeks highs over 115F. Kept in garage that never exceeded 95F.

145.1 miles driven plus, 11 mile remaining at 3.8 m/kWh = 41.08 kWh.

41.08 / 41.8kWh = 98.3% capacity

1.7% degradation at 10,402 miles, 13 months in service.

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 Post subject: Re: Battery Degradation
PostPosted: Sat Apr 12, 2014 10:05 pm 
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Joined: Sun Mar 03, 2013 8:18 am
Posts: 208
Location: SoCal
EVBill wrote:
Link below to Tesla patent issued last month with the title "Electric Vehicle Battery Lifetime Optimization Operational Mode". Provides some interesting info.

http://www.faqs.org/patents/app/20130221916


This is standard practice, how can Tesla patent, something that has been around as long as rechargeable Lithium batteries have been around?

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 Post subject: Re: Battery Degradation
PostPosted: Sat Apr 19, 2014 2:34 pm 
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Joined: Tue Aug 27, 2013 3:21 pm
Posts: 139
On the Rav GOM where is 50% on the meter? Since in 80% charge when full all the bars are there....

is that above the half way mark?

or just below? Or just dead center? (then technically that's 40% right?)

I really need to get cracking this thing open... ughh.. holidays..

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 Post subject: Re: Battery Degradation
PostPosted: Sun Apr 20, 2014 6:05 am 
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Joined: Fri Apr 12, 2013 7:30 am
Posts: 134
Location: Gardena, CA
Hi Jason,

50% is 10/16 bars, so slightly above halfway.

Standard charge (80%) is 16/16 bars and extended charge is also 16/16 bars. Very silly and it would have been nice if they shown some other indication of it an extended 100% charge.


Here's a reference to Tony's posts about that.
viewtopic.php?p=251#p251

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 Post subject: Re: Battery Degradation
PostPosted: Sun Apr 20, 2014 6:08 pm 
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Joined: Tue Aug 27, 2013 3:21 pm
Posts: 139
Just out of curiosity, has anybody measured the pack voltage while charging to see how it correlates to the bar graphs? I just read Tony's link on the gauge and bars,etc but that just seems strange. So really, 50% is 1 to 2 bars above halfway and where I should be leaving the car sit (technically 40-50% so anywhere in between 6 to 8 bars)..

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2012 10kw Dual LQ cooled Brusa powered Leaf "Astro"
10kw Enphase System,SolarWorld Panels, QuickMountPV- ALL USA!! + 3kw SW panels string tie.
I fly drones and R/C..
2014 Rav4 "SuperRav" JdeMO.


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 Post subject: Re: Battery Degradation
PostPosted: Sun Apr 20, 2014 6:24 pm 
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Joined: Mon May 27, 2013 10:02 pm
Posts: 139
Location: San Francisco, CA
Each bar on the RAV4 EV represents 5% SOC. 10 bars is 50%.

Inexplicably, the RAV4 EV engineers did not put bars representing a charge above 80% SOC on the dashboard, so when you do an extended charge to 100% SOC, you will not see any change in the number of bars for quite some time, not until you hit 75% SOC. There are a number of idiosyncratic design decisions with the RAV, but that one is, IMO, certainly the weirdest of the bunch.

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 Post subject: Re: Battery Degradation
PostPosted: Sun Apr 20, 2014 6:37 pm 
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Joined: Tue Aug 27, 2013 3:21 pm
Posts: 139
10-4 on that. Because now of this, I won't be letting the vehicle sit at 4-6 bars like I have been for the last 3 months which is 40-50% on a Leaf (3.82-3.85v).. But a 18650 should be sitting nicely at 3.7v range for 50% storage for avg 2-3% loss per year.

What a wacky gauge... :roll:

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2012 10kw Dual LQ cooled Brusa powered Leaf "Astro"
10kw Enphase System,SolarWorld Panels, QuickMountPV- ALL USA!! + 3kw SW panels string tie.
I fly drones and R/C..
2014 Rav4 "SuperRav" JdeMO.


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 Post subject: Re: Battery Degradation
PostPosted: Mon Apr 21, 2014 1:38 am 
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Joined: Mon May 13, 2013 6:15 am
Posts: 345
Location: Volcano, CA
TonyWilliams wrote:
Just did a full charge to turtle yesterday:

144.4 miles at 3.7 miles per kWh equals 39.0kWh

39.0 / 41.8kWh = 93.3% capacity

6.7% degradation at 20,000 miles, 9 months in service.


So i think a source of error here is that you only have 2 significant digits in the "miles per kWH" number.
If it says 3.7 miles/kwh that means somewhere between 3.65 and 3.74 miles/kwh.
(going beyond 3 significant digits is useless because we only know the battery capacity to 3 sig figures)

Doing the calculation at both extremes:

144.4 * 3.749 miles/kWH = 38.52 kWH = 92.1% = 7.85% degredation
144.4 * 3.650 miles/kWH = 39.56 kWH = 94.6% = 5.35% degredation

So 6.7% +/- 1.3% degradatin is probably the best way to state that.

I'm at about 13K miles and 1 year of service and i think i'm starting to notice a bit of degradation myself, but i dont really have the opportunity to do long constant-speed tests to check it out. I may get to do that when i drive to Los Angeles where i'll be keeping really careful records.

I assume you're getting your mi/kwh number from the little screen that displays every time you turn the car off and you're driving at fairly low speeds to get 3.7mi/kwh?

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