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 Post subject: Re: DC fast charging the 2017 e-Golf twice, back to back
PostPosted: Thu May 03, 2018 11:48 am 
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Joined: Fri Jan 23, 2015 1:18 pm
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Good point about how long to AC charge following DCFC. If you read the manual, it doesn't say how long to AC charge, but just that a DCFC should be followed by AC and ANY length of time on AC would suffice. I agree with your suggestion - charge to 90% on DCFC (which is when you probably should stop anyway to let someone else use the station, and the taper is already dropped the charge rate to around 7 kW), then move to AC for 15 to 20 minutes, then head off to drive 100 miles for your next DCFC stop. I don't see a need to charge to full on AC, especially if don't charge to full routinely outside of your long range trip.

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 Post subject: Re: DC fast charging the 2017 e-Golf twice, back to back
PostPosted: Thu May 03, 2018 1:32 pm 
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Joined: Fri Nov 17, 2017 3:04 pm
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I believed discharging to 0% is not good at first. But this report says discharging to 0% and charge up to 70% results in the best life for the Samsung battery. Why?

https://pushevs.com/2018/04/27/battery- ... s-partial/


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 Post subject: Re: DC fast charging the 2017 e-Golf twice, back to back
PostPosted: Fri May 04, 2018 9:57 am 
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Joined: Wed Apr 04, 2018 12:12 am
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Location: Sunnyvale, CA (NoCa)
ichwoo wrote:
I believed discharging to 0% is not good at first. But this report says discharging to 0% and charge up to 70% results in the best life for the Samsung battery. Why?

https://pushevs.com/2018/04/27/battery- ... s-partial/


As I see it is 70% to 20% the best for battery.

And looks like charging up to 100% is more evil than discharge till 0%. That surprised me.

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 Post subject: Re: DC fast charging the 2017 e-Golf twice, back to back
PostPosted: Fri May 04, 2018 10:09 am 
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Joined: Fri Jan 23, 2015 1:18 pm
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Similar information:

https://electrek.co/2018/05/04/are-you- ... batteries/

Key takeaways: 1) Avoid high temps and 2) Charge to 80% SOC (article indicates 4.05V)

I have read that 3.9V is better than being above 4 V. But, I don't know (yet) what SOC on "fuel gauge" corresponds to 3.9V.

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 Post subject: Re: DC fast charging the 2017 e-Golf twice, back to back
PostPosted: Fri May 04, 2018 11:50 am 
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Joined: Fri Nov 17, 2017 3:04 pm
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YeGolf wrote:
As I see it is 70% to 20% the best for battery.


No. Don't look at the number of recharge cycles alone. Look at the amount of each recharge too. 0-70% gives the most cycles x power per charge.


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 Post subject: Re: DC fast charging the 2017 e-Golf twice, back to back
PostPosted: Sat May 05, 2018 3:03 pm 
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In numerous published reports, including some referenced in this thread, it is assumed that max voltage is 4.2 V and min voltage is 3.0 V. Using this scale, 70% SOC equals 3.84 V and 80% SOC equals 3.96V.

I just took some data from my 2017 e-Golf today, confirmed it has 31.8 kWh of usable battery energy, and the cells are approximately
(took data while charging from 40% to 60% SOC) 3.48 V at 0% SOC and 4.01V at 100% SOC. So, 80% SOC, as per the "fuel gauge" corresponds to a cell charge of 3.90V and 70% corresponds to 3.85V. Charging the e-Golf to 100% is not recommended as 4.01V is still too high.

Some other interesting data: the max voltage the car can take during DCFC is 369V.

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 Post subject: Re: DC fast charging the 2017 e-Golf twice, back to back
PostPosted: Mon Dec 10, 2018 2:19 pm 
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Joined: Thu Nov 16, 2017 4:53 pm
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Wanted to run this one by the regulars here. Looking in taking my 2017 on a 195 mile trip each way later this month. Haven’t done a ton of sustained freeway driving but when I have I’ve been getting 3.8-4.2 miles per kWh. So I figure I’m going to need to add 19-20 kWh each way and AC charge over night at my destination.

My problem is that the route has a 110 mile gap between DC fast chargers other than a 22kw Chevy dealer that only allow customers.

On the way there I’ll need to hit an AC charger for just under an hour to get to the first DC charger (136 miles from home) then just 65 miles to my destination. The hard part is coming back. My plan is to hit the same DC charger and fill to 80% which will be about 10 kWh. Then drive the 110 miles to the next DC charger (with another hour stop at AC in between) where I’d take another 5-10 kw to make it home the last 20ish miles.

Given the vagueness of the “never use DCFC back to back”, curious what the collective thinks of this. Only taking at total of 15-16 kWH total in DC so it should be ok right?


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 Post subject: Re: DC fast charging the 2017 e-Golf twice, back to back
PostPosted: Mon Dec 10, 2018 6:18 pm 
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Joined: Mon Oct 05, 2015 2:01 pm
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tbier wrote:
Wanted to run this one by the regulars here. Looking in taking my 2017 on a 195 mile trip each way later this month. Haven’t done a ton of sustained freeway driving but when I have I’ve been getting 3.8-4.2 miles per kWh. So I figure I’m going to need to add 19-20 kWh each way and AC charge over night at my destination.

My problem is that the route has a 110 mile gap between DC fast chargers other than a 22kw Chevy dealer that only allow customers.

On the way there I’ll need to hit an AC charger for just under an hour to get to the first DC charger (136 miles from home) then just 65 miles to my destination. The hard part is coming back. My plan is to hit the same DC charger and fill to 80% which will be about 10 kWh. Then drive the 110 miles to the next DC charger (with another hour stop at AC in between) where I’d take another 5-10 kw to make it home the last 20ish miles.

Given the vagueness of the “never use DCFC back to back”, curious what the collective thinks of this. Only taking at total of 15-16 kWH total in DC so it should be ok right?


What the collective "think" is on the internet, doesn't matter, they don't warranty your VW e-Golf battery, VW does. Read your owners manual and do what it says. AC recharging balance recharges all the cells, which is very important to maximize the life of the traction battery. VW has you do this, for a very good reason.

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 Post subject: Re: DC fast charging the 2017 e-Golf twice, back to back
PostPosted: Mon Dec 10, 2018 10:09 pm 
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Joined: Fri Mar 27, 2015 4:13 pm
Posts: 1218
Location: Los Altos, CA
tbier wrote:
Wanted to run this one by the regulars here. Looking in taking my 2017 on a 195 mile trip each way later this month. Haven’t done a ton of sustained freeway driving but when I have I’ve been getting 3.8-4.2 miles per kWh. So I figure I’m going to need to add 19-20 kWh each way and AC charge over night at my destination.

My problem is that the route has a 110 mile gap between DC fast chargers other than a 22kw Chevy dealer that only allow customers.

On the way there I’ll need to hit an AC charger for just under an hour to get to the first DC charger (136 miles from home) then just 65 miles to my destination. The hard part is coming back. My plan is to hit the same DC charger and fill to 80% which will be about 10 kWh. Then drive the 110 miles to the next DC charger (with another hour stop at AC in between) where I’d take another 5-10 kw to make it home the last 20ish miles.

Given the vagueness of the “never use DCFC back to back”, curious what the collective thinks of this. Only taking at total of 15-16 kWH total in DC so it should be ok right?

You didn't say where you are and what you expect the outside temperature to be. Chances are, this time of year, it's not a problem at all. The main reason for avoiding back to back charges is heat accumulation. When it's cold outside the battery doesn't get as hot, so it's much less of a worry. Fast charging for one 200 mile trip is not a big deal, especially on a 2017/2018 e-Golf.

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 Post subject: Re: DC fast charging the 2017 e-Golf twice, back to back
PostPosted: Mon Dec 10, 2018 10:27 pm 
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Joined: Sat Jul 25, 2015 2:24 am
Posts: 756
Location: SoCal
Also keep in mind that one time likely isn't going to ruin your battery, as opposed to using DCFC as your primary charging source.

"Sparingly" is the key word here.

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