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 Post subject: Battery degradation 1.3 kw vs 3.3Kw vs 7.2
PostPosted: Tue Jun 11, 2019 1:05 pm 
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Joined: Tue Dec 15, 2015 10:41 pm
Posts: 93
I have been charging my 2016 eGolf over 110 V ( 1.3 Kw) for about 3 years now. Even with my 60 mile commute, it has been more than sufficient. I have seen almost no battery degradation, I can pretty easily still get 90 real world miles, without too much problem.

I now have 2019 eGolf(7.2Kw) and Juicebox Pro 40 ( 10kw capabable). Wondring if folks who have been charging at level 2 speeds have seen any degradation over the years?
Wondering if I should continue charging a 1.3Kw/3.3kw instead of the 7.2kw(capable)

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2016 eGolf | 2019 eGolf SE/DAP | Tesla Model S 90D | 6.5 Kw Solar | JuiceBox Pro 40 | Tesla Mobile Charger


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 Post subject: Re: Battery degradation 1.3 kw vs 3.3Kw vs 7.2
PostPosted: Tue Jun 11, 2019 1:15 pm 
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Joined: Wed Nov 09, 2016 8:28 am
Posts: 13
Location: San Jose, CA
I had my 2016 eGolf charged twice a day (at home and in the office) using level-2 charging to 100%. I have never used L1 charging, nor DC fast charge. After three years I have not seen any significant battery degradation. Since January this year I have a 2019 eGolf with the bigger battery and I am charging now only once a day. So far I have not noticed any degradation.

cheers,
Werner

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VW e-Golf 2016 SEL, JuiceBox Pro 40


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 Post subject: Re: Battery degradation 1.3 kw vs 3.3Kw vs 7.2
PostPosted: Tue Jun 11, 2019 1:37 pm 
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Joined: Mon Nov 02, 2015 2:32 pm
Posts: 640
Location: Santa Cruz, CA
My 2016 SE has no fast charger and L2 is limited to 3.6 kW max.

I spent the first year mostly trickle charging @ 120V, then got the ChargePoint home charger in 2017 at which point almost all charging was L2. I could not measure any degradation in that first year.

It's currently at 25,000 miles and I've calculated my battery capacity at just under 20 kWh now. It's tough to say if L1 vs L2 has mattered, but since folks with LE/SELs are reporting about the same capacity for e-Golfs at this age/mileage I would say that 3.6 vs. 7.2 kW charging does not impact capacity.

However, 1.2 vs 3.6 kW might...

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2016 e-Golf SE in Urano Grey leased 8/1/2016 for $1500 down + $50 x 24 months * Purchased 7/31/2018 * ChargePoint Home 32a (wired)
2018 BMW i3s REx in Mineral Gray purchased 6/12/2018 w/ Giga, Tech, Parking, CarPlay, Harmon Kardons, and of course Moonroof


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 Post subject: Re: Battery degradation 1.3 kw vs 3.3Kw vs 7.2
PostPosted: Tue Jun 11, 2019 3:22 pm 
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Joined: Fri Jan 23, 2015 1:18 pm
Posts: 416
Lithium ion battery cell degradation is primarily a function of temperature, time, and state of charge. You generally want to avoid high cell voltages (above 3.9 V) at high temperatures and want to avoid very low cell voltages at any temperature. As you increase the charge rate, the current going into each cell increases and thus the ohmic heating increases - P=I^2*R so the heat generated by resistance is proportional to the square of the current. Therefore, charging at 7.2 KW will heat the battery significantly more than charging at 1.2 kW.

But, the question is, does the additional joule heating at the higher charge rate matter? I think that depends on the starting temperature of the battery cells. If the ambient temp (and thus the cell temps, given enough time to equilibrate with the ambient environment) is high, then you may want to wait for the pack to cool before you heat it up with 7.2 kW (or 39 kW for that matter), but we don't have any data from VW about this, so who knows? I believe cell temperatures begin to become an issue for degradation around 35 to 40C, and even more so when you have high temps in combination with a high state of charge. In other words, try not to keep you battery above 80% state of charge when the ambient temps are near or above 100 F.

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Last edited by f1geek on Tue Jun 11, 2019 5:01 pm, edited 1 time in total.

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 Post subject: Re: Battery degradation 1.3 kw vs 3.3Kw vs 7.2
PostPosted: Tue Jun 11, 2019 3:40 pm 
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Joined: Tue Dec 15, 2015 10:41 pm
Posts: 93
Nice analysis.

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2016 eGolf | 2019 eGolf SE/DAP | Tesla Model S 90D | 6.5 Kw Solar | JuiceBox Pro 40 | Tesla Mobile Charger


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 Post subject: Re: Battery degradation 1.3 kw vs 3.3Kw vs 7.2
PostPosted: Tue Jun 11, 2019 5:06 pm 
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Joined: Mon Oct 05, 2015 2:01 pm
Posts: 2292
I think age will also eventually be a factor of cell charging degradation.

I don't believe letting the battery sit with the gauge at 100% full tank and the battery at whatever it actually is charged to, 4.05 V or a bit more, (90 -91%) is good for longevity either. Which is why timed charge being complete right before you leave to drive in the morning is probably a very good thing for the longevity of your battery.

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