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 Post subject: Re: Estimating Battery Degradation
PostPosted: Tue Nov 21, 2017 12:33 pm 
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Joined: Sat Oct 03, 2015 7:27 pm
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Location: NJ
Thanks for posting these updates. My daily charge is 80% - 90% in winter - and I don't drive a lot of miles (14k in 2 years) so I don't really see degradation.

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Still Plays With Cars - '15 e-golf, '04 V70R, '04 FFR, '01 360, '91 318is


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 Post subject: Re: Estimating Battery Degradation
PostPosted: Thu Nov 30, 2017 6:12 pm 
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Joined: Fri Jan 23, 2015 1:18 pm
Posts: 397
I found some interesting information:

https://avt.inl.gov/sites/default/files ... empBOT.pdf

According to this test lab, the battery has 75 Ah total capacity, and I found in the 2015 e-Golf battery warranty, VW says the initial net capacity is 64 Ah, so maybe I was wrong about the initial net capacity being 21.76 kWh (about 90% of gross). If we assume that the initial net capacity is 64/75=0.853 (85.3% of gross capacity), that equates to 20.65 kWh net usable battery capacity. If this is true, then if my car is currently at 18.4 kWh net capacity, then it has only lost 11% of its initial capacity. If I assume a linear rate of capacity loss, then it may still be at 70% net capacity in 8 years, but then again, it may not. There's also the possibility that the rate of degradation will either increase or decrease with time and not follow a linear relationship.

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 Post subject: Re: Estimating Battery Degradation
PostPosted: Thu Nov 30, 2017 10:57 pm 
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Joined: Fri Mar 27, 2015 4:13 pm
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Location: Los Altos, CA
I looked at the BEV tests that they did across several vehicles and was disappointed to find that they don't run the same tests on all the cars. For the e-Golf they focused on fast charge performance at different temperatures, but for other vehicles they focused on other aspects of the vehicle performance. It would have been nice to see the fast charge performance of other vehicles on the same tests that they ran on the e-Golf, especially vehicles with battery pack active thermal management.

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 Post subject: Re: Estimating Battery Degradation
PostPosted: Thu Dec 14, 2017 7:19 pm 
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Joined: Mon Oct 05, 2015 2:01 pm
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Ran my car down to 5 miles left on the Guess-O-Meter. Last full fillup showed 6 .0 miles per kwh. Recharged fully with e-motorwerks 40 Pro JuiceBox. JuiceNet log shows 20.56 KW used to recharge. Efficiency is about 91%, So I added 18.71 kW to the battery on that recharge. 5 miles left would indicate .83 usable kW still in the battery. About 19.54 kwh current useable battery capacity at 6.0 miles per Kwh = 117 miles of "range". Exactly what my guess o meter is currently showing on a full recharge. So, that's what my current usable battery capacity is after 14500 miles and 26 months of ownership. 19.54kWh. Car had about 21.3 kWh when brand new.

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 Post subject: Re: Estimating Battery Degradation
PostPosted: Wed Jan 03, 2018 1:18 pm 
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Joined: Fri Jan 23, 2015 1:18 pm
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Anybody find a way to use an OBD device, such as OBDEleven, to get a read on the battery health (capacity)?

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 Post subject: Re: Estimating Battery Degradation
PostPosted: Thu Jan 04, 2018 4:13 pm 
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Posts: 25
Another data point:

[*]23 months, 14,000 miles, estimated degradation 6-8% based on charging/range info.
[*]e-Golf is only being charged with L2. It typically is being recharged to 100%, and sometime reaches 5-10 miles range before being charged again (function of commuting).
[*]Regen is B or D3, if used.

Side note on regen impact: It would be interesting to understand if using max regen (B) really impairs the battery. Theoretically, this makes sense. But would VW not limit potential damage/aging to the battery by capping regen based on whatever appropriate metric (temperature, cycles, etc.)? One would think that VW would not be interested in a wave of claims regarding prematurely aging/failing batteries.

With the warranty at 70% for 100,000 miles/8 years, it is conceivable that some of e-Golfs will reach the 70% threshold before the distance/age. And would this be 70% of 24.2 kWh (=16.94 kWh)? Also interesting - would a dealer be able to update the battery management to open the discussed "reserve", by this ensuring a 70% plus capacity level?


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 Post subject: Re: Estimating Battery Degradation
PostPosted: Thu Jan 04, 2018 5:46 pm 
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I vaguely remember reading that max regen on the e-Golf is around 40 kW. While the high regen found in B mode will send more 40 kW spikes into the pack, I don't believe it would generate the same amount of heat from DCFC charging where 43 kW (at a 125 amp DCFC station) is sustained continuously for 20 to 30 minutes. Heat is what speeds up the pack degradation.

VW warrants the NET capacity. Based on a European e-Golf manual I got my hands on, it says the starting net capacity is 64 Amp hours. AT 323 V nominal pack voltage, that translates into 20.7 kWh starting net capacity. Therefore, 70% of 20.7 is 14.5 kWh. But I could be wrong about the correct starting net capacity.

I suspect that the "reserve" capacity is automatically activated by the battery management software once the health of the battery degrades to a certain level. Of course, once that happens, the battery health will then decline even faster than before.

Based on my net capacity measurements, my car has about 19 kWh of usable capacity (about 10% loss), after 24,000 miles and almost three years. I'm not sure the warranty will be triggered but since it's getting hotter in the SF Bay Area, I think the battery will be taking a beating over the next several summers, and the capacity may drop faster than it already has.

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 Post subject: Re: Estimating Battery Degradation
PostPosted: Sat Jan 06, 2018 4:36 pm 
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Joined: Fri Jan 23, 2015 1:18 pm
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I just got OBDEleven Pro. I found that at "Full" on the battery gauge, actual battery SOC is 97.2%, according to the car computer. Also, the battery voltage is 357 Volts (each of the 88 cells was at 4.06 V). If only there were a way to find out the total amp hours of the pack... Anyone know if this live data can be found somewhere?

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 Post subject: Re: Estimating Battery Degradation
PostPosted: Sat Jan 06, 2018 5:20 pm 
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f1geek wrote:
I just got OBDEleven Pro. I found that at "Full" on the battery gauge, actual battery SOC is 97.2%, according to the car computer. Also, the battery voltage is 357 Volts (each of the 88 cells was at 4.06 V). If only there were a way to find out the total amp hours of the pack... Anyone know if this live data can be found somewhere?
Full charge should be 4.20V per cell. 4.06 is a good compromise, and adds considerably to the lifetime of the battery.

I just try to recharge it at an hour or more in time, for the 2015 to 2016 24.3 kwh batteries, the Charge Point 100 DC level 2 chargers are just fine rated at 24 kWh. The highest I have seen a Charge Point DC 100+ charge my e-Golf is 21.2 kWh rate. The 2017 e-Golf can take probably 33 to 35 Kwh charge on board probably pretty comfortably.

Any Lithium Ion battery that stays cool should be fine with a recharge to 90% SOC in a 1 hour time limit window. Key is staying cool while recharging, and only a 90% SOC when finished.

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 Post subject: Re: Estimating Battery Degradation
PostPosted: Sun Jan 07, 2018 10:43 am 
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Joined: Fri Jan 23, 2015 1:18 pm
Posts: 397
According to the Idaho National Laboratory, the maximum voltage of the e-Golf battery pack is 4.10 volts, not 4.2 volts. The minimum voltage is 3.00 volts.

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