DC fast charging the 2017 e-Golf twice, back to back

[mfennell]

So the most you can put into that e-Golf battery is 91%.

Please provide a source for that.

Several people have estimated the early cars use ~22kwh of the ~24kwh pack which is about 91% (and where you got that number, I assume) but there is no way VW would go from true "zero" to 91%. That would be crazy and begging for bricked cars.

Get back to me when your battery on your 2017 is 3 years past the build date. By 18 months, my range was down to 121 miles. By 30 months it's down to 117 to 119.

While you may have a loss of range, you have no tools to accurately assess it. You're mistaking the guess-o-meter for a precision instrument.

That said, any degradation of my own battery at 30mos/17000 miles is outside my ability to measure. I almost never charge to 100% (maybe 10 times total) and I leave it in the middle when I'm not driving for a few days. I aim to arrive at work a bit below 75% and manipulate the charge throughout the year as necessary.

 

[msvphoto]

What scan tools show voltage of the battery?

I have not tried connecting my VCDS (VAG COM) since it is pre-CAN Buss, but maybe it would show some modules?

Otherwise I am buying yet another scan tool, and this would be for curiosity mostly since the e-Golf is outside the scope of my "fleet maintenance" which, thanks to getting the e-Golf, has recently been reduced to just three ICE cars (and I am on wrenching Injured Reserve thanks to an ankle that needs surgery).

Will Carista or OBD11 show battery voltage? Is the key to confirm 80% of 4.2v cell voltage, or???

For now maybe best I heed the advice and dial back max charge since thus far we have been charging to 100%. I warned the "user" of said car not to go too low before recharge and she is doing pretty good there. (I had the same battle over running ICE cars on fumes and every time I did a fuel pump job I would complain a little.)

 

[msvphoto]

Follow on question. If I set minimum charge to 20% and plug in below 20% with a charge departure timer set, does the car charge to 20% and stop until the departure timer takes over, or will it charge to the max charge setting?

I changed max charge to 80% from 100% in carnet. If I know I need the extra charge on a given day can I simply press the charge button in the charge port to resume after it automatically stops at 80%

We own (not a lease) the car and plan to keep it a while, trying to preserve the battery makes sense on a lot of levels.

 

[f1geek]

I use OBDEleven scan tool. It shows the pack voltage and also the voltage of each of the 88 individual "cells" (there are 264 37 Ah cells in the pack, but some are arranged in parallel groups of three or four cells, I beleive, so there are 88 "cells" in series per the scan tool). It also shows usable capacity in Wh, and shows pack temperature, current draw, etc. I have limited SOC vs voltage data and I need to get more information so I can get a sense of max and min voltages.

Yes, car will immediately charge to minimum charge level % and then go to sleep until required to wake up later to meet max charge % setting at programmed time.

 

[JoulesThief]

So the most you can put into that e-Golf battery is 91%.

Please provide a source for that.

Several people have estimated the early cars use ~22kwh of the ~24kwh pack which is about 91% (and where you got that number, I assume) but there is no way VW would go from true "zero" to 91%. That would be crazy and begging for bricked cars.

Get back to me when your battery on your 2017 is 3 years past the build date. By 18 months, my range was down to 121 miles. By 30 months it's down to 117 to 119.

While you may have a loss of range, you have no tools to accurately assess it. You're mistaking the guess-o-meter for a precision instrument.

That said, any degradation of my own battery at 30mos/17000 miles is outside my ability to measure. I almost never charge to 100% (maybe 10 times total) and I leave it in the middle when I'm not driving for a few days. I aim to arrive at work a bit below 75% and manipulate the charge throughout the year as necessary.

When you average 6.1 miles per kWh, run the car battery down to 6 miles left (Est 1 kW left) and you've traveled 111 mile on said charge, it's safe to think you might have 19 kWh capacity left on your battery. If you do this and just are at reserve, or about 2 kW left with 104 to 107 mile showed traveled and 12 to 9 or 10 miles left, several times during the summer, I think that the data indicates what's left for capacity in your battery, short of running it until the turtle dies.

I really think VW runs charging levels to make the car idiot proof for owners and leasees, such that they aren't going to be eating warranty work on replacement batteries under warranty, with what they call "full" charging.

 

[Kieran973]

Sorry, f1geek, I just want to make sure I 100% understand you. How are you planning on managing your own charging during long, 250ish mile trips? You mentioned you'll do at least one a year. Mostly what I mean is:

1. What SoC would you charge to immediately before your departure?
2. What SoC would you charge to for your DCFC along the way?
3. What SoC would you charge to for your post-DCFC AC charge?

Some people recommend charging to 100% 15-30 minutes before you leave, that way you have maximum range but your battery also isn't sitting at 100% for that long. Is this OK in your book? Or is it the act of charging to 100% at all which is damaging?

Also, when doing that AC charge that comes after every DC charge, what's the minimum amount of time or the minimum amount of SoC required in order for this charge to count? Like could I DC charge to 80%, then AC charge for just 60 seconds or 1% more? Or does this follow-up AC charge need to be more substantial, and if so, how much? I believe JoulesThief suggested about 25-30 minutes.

 

[JoulesThief]

Sorry, f1geek, I just want to make sure I 100% understand you. How are you planning on managing your own charging during long, 250ish mile trips? You mentioned you'll do at least one a year. Mostly what I mean is:

1. What SoC would you charge to immediately before your departure?
2. What SoC would you charge to for your DCFC along the way?
3. What SoC would you charge to for your post-DCFC AC charge?

Some people recommend charging to 100% 15-30 minutes before you leave, that way you have maximum range but your battery also isn't sitting at 100% for that long. Is this OK in your book? Or is it the act of charging to 100% at all which is damaging?

Also, when doing that AC charge that comes after every DC charge, what's the minimum amount of time or the minimum amount of SoC required in order for this charge to count? Like could I DC charge to 80%, then AC charge for just 60 seconds or 1% more? Or does this follow-up AC charge need to be more substantial, and if so, how much? I believe JoulesThief suggested about 25-30 minutes.

It's OK to charge fully on AC, IF you plan to get in the vehicle again immediately or shortly after it completes, within an hour, and start using it so it's not sitting at the full charge capacity for too long, say within 30 min or an hour. For the AC charge to count as "every other", you should try to get a full charge, or close to a full recharge, into the battery.

 

[f1geek]

1. I'm going to set the charge timer to hit 100% about 30 minutes before I leave.
2. I plan to DCFC after 94 miles of highway travel (which will be around 20% SOC, I'm guessing). I want to hit 90% SOC before I leave.
3. I'll AC charge 50 miles later because I don't have many other options. I plan to hit 90% SOC before I leave. The last leg of my trip is 75 miles but the final 40 miles of that leg are 5000 feet up a mountain. At the top of the mountain, I'll trickle charge the car to 70% SOC in preparation for the regen down the mountain several days later.

The less time the pack spends at 100%, the better.

The AC charge should be to a level you need to get to your next destination, so if you need 80%, then go for 80%, but if you need 100% to stretch the distance, go for 100%. If you don't need to charge to 100%, then it makes no sense to charge to full - if you spend several hours filling the battery at L2, the battery won't overheat because even at 7.2 kW (0.23C) the pack temp shouldn't rise much - in fact, it may drop due to the endothermic nature of low C charging below 80% SOC.

FYI, at highway speeds, pack heat generation is relatively constant from 100% down to 20% SOC, but as the SOC drops below 20%, the rate of heat generation goes up quite subtantially, due to joule heating and the exothermic nature of the discharge process.

 

[Kieran973]

Got it, thanks for clarifying. And that all sounds like a good, well thought-out plan.

The reason I was asking about the length of the follow-up AC charge was actually to save time - I would like to AC charge for as few minutes as necessary before getting back on the road. Originally, when I started looking at the e-Golf seriously, I thought a 250 mile trip would be no problem: charge to 100% right before leaving, drive 100 miles, DCFC for 20-30 minutes to 80-90%, drive another 100 miles, DCFC a second time for 20-30 minutes to 80-90%, drive the last 50 miles, and then AC charge at the destination. But since this second charge apparently has to be an AC charge rather than DC, this throws a wrench in that plan, and potentially means a 2-3 hour AC charge in the middle of this trip. Since my wife and I have a baby on the way, this seems like a whole lot of not-fun.

JoulesThief's suggestion is an interesting one: immediately after that first 90% DCFC, switch to a 20-30 minute AC charge at the same charging station, then get back on the road. That way, the next time you stop to charge, it can be a DC charge again.

In general, it seems to me that if charging to 100% is bad for the battery, then a "healthy" charge (whether DC or AC) is always a partial charge. So then the amount of this partial charge (whether measured in minutes or SoC gained) seems kind of arbitrary - as long as it's partial and not 100%, it's "healthy." So this had me wondering: to save time, could your partial AC charge be 60 seconds? Could it be 20 seconds? What's the minimum amount of time or SoC gained necessary for this partial AC charge to count as "alternating" between DC and AC charges? JoulesThief suggests that for this AC charge to count as "alternating", it has to be a full charge, or almost full charge. But then this seems to mean that a 100% AC charge is not just tolerable as long as you drive off 30 minutes later, but actually the ideal, "healthy" SoC for an AC charge....

 

[JoulesThief]

Got it, thanks for clarifying. And that all sounds like a good, well thought-out plan.

The reason I was asking about the length of the follow-up AC charge was actually to save time - I would like to AC charge for as few minutes as necessary before getting back on the road. Originally, when I started looking at the e-Golf seriously, I thought a 250 mile trip would be no problem: charge to 100% right before leaving, drive 100 miles, DCFC for 20-30 minutes to 80-90%, drive another 100 miles, DCFC a second time for 20-30 minutes to 80-90%, drive the last 50 miles, and then AC charge at the destination. But since this second charge apparently has to be an AC charge rather than DC, this throws a wrench in that plan, and potentially means a 2-3 hour AC charge in the middle of this trip. Since my wife and I have a baby on the way, this seems like a whole lot of not-fun.

JoulesThief's suggestion is an interesting one: immediately after that first 90% DCFC, switch to a 20-30 minute AC charge at the same charging station, then get back on the road. That way, the next time you stop to charge, it can be a DC charge again.

In general, it seems to me that if charging to 100% is bad for the battery, then a "healthy" charge (whether DC or AC) is always a partial charge. So then the amount of this partial charge (whether measured in minutes or SoC gained) seems kind of arbitrary - as long as it's partial and not 100%, it's "healthy." So this had me wondering: to save time, could your partial AC charge be 60 seconds? Could it be 20 seconds? What's the minimum amount of time or SoC gained necessary for this partial AC charge to count as "alternating" between DC and AC charges? JoulesThief suggests that for this AC charge to count as "alternating", it has to be a full charge, or almost full charge. But then this seems to mean that a 100% AC charge is not just tolerable as long as you drive off 30 minutes later, but actually the ideal, "healthy" SoC for an AC charge....

I would suggest this, from a logical, legal POV standpoint. Your AC charging TIME should EQUAL or EXCEED your DC charge time on that back to back charge. That way you have given both charging means EQUAL or more consideraton. If time is so precious, take the gas car. The Electric car should be used in such a manner that recharging it is never an inconvenience or waste of your time, or preventing you from multitasking for more efficiency. If charging time with a baby on board is a problem, find another means of transportation, if battery warranty is so important to you. You are beating a dead horse here.
i
Charging to 100% is not bad.... if you get on the road again shortly and use the top charge quickly. STORING at 100% for overnight or more than a few hours is what is NOT as good for the traction battery. Reread what f1geek wrote a few times over, until it sinks in and you comprehend what he's getting at.

 

[f1geek]

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.

 

[ichwoo]

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-charging-full-versus-partial/

 

[YeGolf]

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-charging-full-versus-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.

 

[f1geek]

Similar information:

https://electrek.co/2018/05/04/are-you-killing-your-lithium-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.

 

[ichwoo]

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.

 

[f1geek]

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.

 

[tbier]

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?

 

[JoulesThief]

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.

 

[miimura]

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.

 

[RonDawg]

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.