Volkswagen e-Golf Forum

Battery degradation
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Author:  alexecar [ Fri Nov 17, 2017 2:33 pm ]
Post subject:  Battery degradation


I drive a 2016 e-Golf SE and have reached 23 months and 22k miles of my 36 month/36k mile lease. I do notice a degradation of battery, and my 60 mile round-trip commute is starting to get close if I drive the speed limit. I know that I can drive more conservatively, but I like to arrive quickly ;-)

After today's drive, the car showed the following statistics "Since charge":

Distance 60 mi
Time 1:06 h
Avg speed 54 mph
Avg consumption 3.6 mi/kWh
Remaining distance 6 mi

Temperature here today is 46-60 F

Calculating the total battery capacity based on this: 66 mi / 3.6 mi/kWh = 18.3 kWh
Percentage from original capacity: 18.3 / 24.2 = 75.8%

I understand that the e-Golf has a 70% capacity battery warranty, so I still have 5.8% to go lower.

Here are my questions:
- Is there a more accurate way to get the current battery capacity, what does VW use to check for warranty claims? I have a OBD2 tool for VW cars, if this is necessary.
- Any other experiences with battery warranty claims, any reasons why VW would deny them even if you are down to under 70% ?


Author:  f1geek [ Fri Nov 17, 2017 3:07 pm ]
Post subject:  Re: Battery degradation

The correct calculation is, assuming you have 6% left, 66/3.6/0.94=19.5 kWh estimated usable capacity. Of course, a few % difference in SOC (State of Charge) can make a difference in the calculation. Also, VW warrants NET capacity. Assuming the net capacity when new is 90%, then the starting net capacity is 21.8 kWh. Therefore, you are at 19.5/21.8=89%, not 76%. You're going to have to wait a bit longer for the degradation to hit 70% of net capacity (~15.3 kWh).

I wish there were a more accurate way to get current net capacity. I've called VW about this and they say only a dealer will provide warranty net capacity data and if you haven't reached 70% or lower, then you will probably be charged for this information. If you are able to get it via OBD, could you please post this method to the forum?

I don't have any experience with VW warranty claims, but based on the their company culture (diesel emissions cheating), I'm guessing it will be like pulling teeth to get a replacement battery free of charge. Also, if you read the warranty, VW only promises to replace the defective battery with one that has no less than 70% net capacity, so it seems to me e-Golf owners are screwed and the best range you'll be able to get with a "new" battery is 55 miles (with no charge remaining) the way you are currently driving.

The only thing you can realistically do right now is to either slow down, use less energy in the car (turn off A/C or heat) or drive in ECO mode. ECO+ will limit top speed, so you probably won't enjoy that mode.

Best of luck!

Author:  miimura [ Fri Nov 17, 2017 6:35 pm ]
Post subject:  Re: Battery degradation

^^^ This. I could not have said it better.

Author:  JoulesThief [ Sat Nov 18, 2017 12:13 am ]
Post subject:  Re: Battery degradation

Averaging 54 mph means you're hauling ass to get that kind of average, including time at stop signs, stop lights, and offramps, and general street non freeway traffic. You're probably never driving the speed limit anywhere to achieve that kind of average, at least in California. You have to be driving on side streets and residential streets somewhere.

Get out of B or D3 or D2 or D1 mode, if you are using them coast a bit more, and see if your range per recharge increases.

Author:  alexecar [ Mon Nov 20, 2017 9:17 am ]
Post subject:  Re: Battery degradation

Thanks for all responses. Too bad there is no straight way to get battery capacity.
My commute is 29 out of 30 miles freeway, with just 2 traffic lights and one stop sign. I can get 54mph average easily without going much over 65, at least at 6am and earlier ;-)

Author:  JohnCegolf [ Mon Nov 20, 2017 9:56 am ]
Post subject:  Re: Battery degradation

My question is: Will the computer adjust your projected miles on a full charge based on your driving habits?
Meaning if you started to drive conservative, will the projected miles on a full charge begin to increase?
I've noticed since I started driving on the highway my miles have dropped from 92 to 60 in a matter of two weeks. I can't see another reason.

Author:  f1geek [ Mon Nov 20, 2017 10:57 am ]
Post subject:  Re: Battery degradation

Yes, the e-Golf's GOM (Guess-O-Meter) provides a guess of the range based on your recent driving habits. If I drive on the highway, the GOM displays a much lower range estimate than if I drive around town at low speeds. When I drove down a mountain, the range estimate was ridiculously high for a few hours before the computer recalculated based on driving on a flat road. I believe most EVs provide a range estimate this way.

Author:  Spektre [ Wed Jul 10, 2019 11:54 am ]
Post subject:  Re: Battery degradation

Yes, old thread here, I know, but I liked the title. I'm aware of the other threads including Estimating Battery Degradation and Have you experienced battery degradation?

Many thanks to f1geek and others for explaining how to calculate degradation. I'm going to get religious about it, but I've been lazy calculating my degradation until now. My first calculation is from yesterday:

38 miles driven @ 3.9mi/kWh, 38% remaining when I got home (from CarNet) = 15.7kWh est.

I'll keep gathering data, but it looks like I'll hit the warranty point sometime this year - I'm currently at 51,749 miles.

This should be fun...

Author:  f1geek [ Wed Jul 10, 2019 1:04 pm ]
Post subject:  Re: Battery degradation

Thanks for the update. You will probably get a more accurate estimate of usable capacity if you drain the capacity closer to 10% (or less, if you dare). Also,there is the assumption that you charged to 100% prior to starting your trip - you may want to check the CarNet SoC at full charge, because when I charged my car to "full" on the analog gauge, the OBDII data said 96% SoC (did not check CarNet for a value).

Author:  Sparklebeard [ Wed Jul 10, 2019 6:40 pm ]
Post subject:  Re: Battery degradation

Do you have OBD11? Based on another thread on here I did some digging and I'm currently trying to figure out the Wh figures listed on module 19.

There's some speculation that the SOH_Q and SOH_P figures somehow tie into battery degradation. I did some math here based on my cars, extrapolating out from the figures I saw listed in OBD11.

The math here seems to work out to suggest that the cars leave the factory with about 90% of the battery available for use when 'fully charged' on the battery gauge. The "Energy storage unit SOC" strongly seems to be listing the vehicles current state of charge in Wh, and this was supported not just through the math working but also observing the figure drop 300Wh (in 100Wh increments) over some period of time with the car running and me monitoring figures in OBD11.

The HV battery charge state figure matches the figure shown in CarNet, so this must be the "user facing" SOC, not the absolute cell SOC.

(12/18 build plate)
2852 mi
Energy storage unit SOC: 15475 Wh
HV battery Charge State: 49.0
SOH_Q: 97%
SOH_P: 97%

[Calculated usable capacity today]: 31581 Wh (15475/49*100)
[Calculated usable capacity at factory]: 32558 Wh (31581/97*100)

(08/16 build plate)
26,154 mi
Energy storage unit SOC: 15000 Wh
HV battery Charge State: 80.0
SOH_Q: 87%
SOH_P: 87%

[Calculated usable capacity today]: 18750 Wh
[Calculated usable capacity at factory]: 21551 Wh

Anyone else with OBD11 or VCDS please feel free to add your figures to this, it would be great if we did find a way to diagnose battery health without relying on the trip computer.

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