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

[manybees]

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.

Curious where I can find more information about AC recharging doing a "balance recharge" of the cells of the battery. Could you point me to further info? I have a 2018 e-Golf, and the owner's manual mentions absolutely nothing about "balance recharging."

 

[manybees]

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.

The 2018 e-Golf owner's manual states that "Frequent and consecutive high-voltage charging (DC fast charging) can permanently decrease the capacity of the high-voltage battery. Therefore, always alternate high-voltage charging (DC fast charging) and low-voltage charging (AC charging)."

This logic seems a bit confusing to me. What about infrequent, consecutive DCFC? Will that permanently decrease capacity? If only "frequent and consecutive" DCFC decreases capacity, why would the conclusion be to "always" alternate DCFC and AC charging?

 

[f1geek]

The manual is not clear, I believe, because VW doesn't really want to tell you what consecutive DCFC sessions are doing to the battery pack, that is, making it very hot. If you are suggesting that "infrequent" charging would look something like a DCFC session on Sunday and no charging during the week, followed by another DCFC session the following Sunday, then I believe that while there may be some degradation, the degradation will be less severe than if you drive 120 miles, DCFC, drive another 120 miles, DCFC, etc. VW wants you to always alternate AC charging because the heat buildup with AC charging is MUCH less than with DCFC charging due to a dramatically lower amperage (and thus power dissipated due to internal resistance, and thus heat generation) than a DCFC session. Since there is no temperature gauge, VW can't tell you to keep the temperature below "X". Also, VW has a warranty and doesn't want to pay for a battery pack under warranty if you've abused the car. The e-Golf has no active cooling system, so once the temperatures in the pack rises, the pack cools relatively slowly. High temperatures and high SOCs are what lead to battery degradation and the combination of the two lead to even more degradation.

The fact is, the battery capacity will permanently decrease regardless of what you do - there is calendar life decrease and use decrease. Of course, if the car sits mostly unused for a year at a mid-SOC (say, 50%), the loss in capacity will be much less than actively cycling the pack, either through AC charging or DC Fast Charging. But we all bought the car to drive it, I'm guessing, so that's probably an unlikely use case scenario.

 

[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.

The 2018 e-Golf owner's manual states that "Frequent and consecutive high-voltage charging (DC fast charging) can permanently decrease the capacity of the high-voltage battery. Therefore, always alternate high-voltage charging (DC fast charging) and low-voltage charging (AC charging)."

This logic seems a bit confusing to me. What about infrequent, consecutive DCFC? Will that permanently decrease capacity? If only "frequent and consecutive" DCFC decreases capacity, why would the conclusion be to "always" alternate DCFC and AC charging?

What VW is saying is don't think it's like a Tesla and you can quick charge all the time. But an occasional DCFC, even if if subsequent, is OK if done sparingly, hence the term "frequent AND consecutive."

If VW doesn't want you to DCFC, they wouldn't include a DCFC port. BTW you can "alternate" at most DCFCs as there's usually an L2 nearby, and it's considered EV etiquette to only DCFC to 80% and then L2 the rest of the way, since above 80% the charging speed drops dramatically.

 

[manybees]

The manual is not clear, I believe, because VW doesn't really want to tell you what consecutive DCFC sessions are doing to the battery pack, that is, making it very hot. If you are suggesting that "infrequent" charging would look something like a DCFC session on Sunday and no charging during the week, followed by another DCFC session the following Sunday, then I believe that while there may be some degradation, the degradation will be less severe than if you drive 120 miles, DCFC, drive another 120 miles, DCFC, etc. VW wants you to always alternate AC charging because the heat buildup with AC charging is MUCH less than with DCFC charging due to a dramatically lower amperage (and thus resistance, and thus heat generation) than a DCFC session. Since there is no temperature gauge, VW can't tell you to keep the temperature below "X". Also, VW has a warranty and doesn't want to pay for a battery pack under warranty if you've abused the car. The e-Golf has no active cooling system, so once the temperatures in the pack rises, the pack cools relatively slowly. High temperatures and high SOCs are what lead to battery degradation and the combination of the two lead to even more degradation.

Thanks for that clear and directly stated summary, @f1geek. Very helpful and useful information, indeed.

Do you think that the DCFC heat issue would be reduced during winter driving -- esp. with ambient temperatures at around freezing or below? Or is the battery slow to cool even in winter? Just wondering whether or not the risk of doing consecutive DCFC sessions back to back on a single trip might be lower due to low ambient temps.

 

[f1geek]

Yes, since high temps kill batteries, specifically above ~40 C, I believe using DCFC in winter temperatures is far less of a problem than in, say, Arizona in the summer. Additionally, since the rate of battery cooling is a function of the delta T between battery core temp and ambient temps, the battery pack will cool more quickly with a larger delta T thanks to cold ambient temps. I have seen anecdotal research that Nissan Leafs operated in the Northern latitudes, like Norway and Canada, have experienced far less degradation than those Leafs operated in the US Southwest - I believe this is directly related to ambient temperatures. Like the e-Golf, the Leaf doesn't have active battery cooling; unlike the e-Golf, which uses either Panasonic or Samsung SDI battery cells, Nissan designed their own cell chemistry, which I believe is inferior, especially with respect to high temperature tolerance, to the cells in the e-Golf. Yes, I believe back to back DCFC in winter temps will raise temperatures less than in the summer, partly since the pack starts at a lower temp and partly because it cools faster in between charging sessions. You can purchase a dongle/OBDII software to monitor battery temps if you are so inclined, but the software is a bit slow and klunky, in my experience.

 

[rd7575]

Consider that the pack is a huge mass for its cooling surface area. Even if it's extremely cold out, the cells in the center of the pack probably aren't going to cool completely, or even much at all, in the time between a DC fast charge and the quick discharge that'd happen on a road trip. (Two-ish hours)

 

[JoulesThief]

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.

Curious where I can find more information about AC recharging doing a "balance recharge" of the cells of the battery. Could you point me to further info? I have a 2018 e-Golf, and the owner's manual mentions absolutely nothing about "balance recharging."

Try Google, manybeers

https://batteryuniversity.com/learn/article/bu_803a_cell_mismatch_balancing

 

[Sparklebeard]

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.

I feel like you might be pulling that out of your donkey, mate. You also don't warranty the battery. The manual definitely warns of potential damage if you overuse DCFC but you keep saying the battery warranty is void if you to back to back DCFC, and you also imply that doing it back to back even once would void the battery warranty.

Link to the VW warranty document that actually explicitly spells that out. Warning that "Frequent consecutive fast charging can damage the battery" is a fundamentally different statement to "back to back fast charging without using an AC charge in between will void your warranty."

From the 2015 e-Golf manual:
"Frequent and consecutive high-voltage charging (including DC charging) can permanently de- crease the capacity of the high-voltage battery. Battery capacity will decrease if you frequently and consecutively charge your vehicle at a DC charging station. Therefore always alternate high-voltage charging (including DC charging) and low-voltage charging. For example, you can charge your vehicle overnight at an AC charging station or use an AC Wallbox if the vehicle was charged at a DC charging station during the day."

Does it clearly, strongly recommend alternating high voltage and low voltage charging? Absolutely! Does it mention warranty implications from taking an infrequent trip that requires back to back DCFC? It does not. Does it say to always AC charge between DC? Sure, and that's definitely the best practice, Still doesn't mean infrequently doing it will void the warranty.

But there's more! This is all it says in my 2016 manual:
"Frequently charging the vehicle with a high charging power, particularly with a direct current (DC charging), can lead to a permanent reduction of the charging capacity of the high-voltage battery. If possible, charge the vehicle with low charging power, like with a home-charging station or with the supplementary charging cable."

I don't believe there are any fundamental chemical or design differences between the 2015 and 2016 battery systems. The only difference is the much softer, but still clear recommendation to use AC charging as much as possible. They actually don't mention back to back DCFC at all in the 2016 manual. So if OP were to take your advice and

Read your owners manual and do what it says.

it might say something different to what you expect it to, and if it's anything like the manual for mine, it would be totally possible to make an infrequent trip like that one described while still following the directions of the manual. I also notice how you follow up "read the owners manual" with a claim about AC charging that is completely missing from the owners manual. While I'm confident the e-Golf does cell balancing, the manual says nothing about it and its definitely not given as the reason not to consecutively DCFC charge.

 

[JoulesThief]

Paragraph closes with:

" If possible, charge the vehicle with low charging power, like with a home-charging station or with the supplementary charging cable.".

The closing statement in a paragraph is what they most want to leave on your mind, to remember. You do what ever you want with your LiPo batteries. Anyone that's played with RC toys and LiPo batteries knows the drill. Quick charging generates heat, internally, in the center mass of batteries like in an e-Golf. That heat is damaging. Hence the "If Possible recommendation. It's pretty well known in LiPo chemistry batteries that exceeding a 1C charge rate is really hard on the life of LiPo chemistry batteries.

Read a whole bunch more on Battery University. Fast charging is a convenience, but it's damaging, for the convenience, the battery's life and reducing it's capacity.

My take away from the above in bold is this.... use your home charging station if at all possible. Not public charging facilities. It's that simple... recharge at home, not in public.

 

[Sparklebeard]

Paragraph closes with:

" If possible, charge the vehicle with low charging power, like with a home-charging station or with the supplementary charging cable.".

The closing statement in a paragraph is what they most want to leave on your mind, to remember. You do what ever you want with your LiPo batteries. Anyone that's played with RC toys and LiPo batteries knows the drill. Quick charging generates heat, internally, in the center mass of batteries like in an e-Golf. That heat is damaging. Hence the "If Possible recommendation. It's pretty well known in LiPo chemistry batteries that exceeding a 1C charge rate is really hard on the life of LiPo chemistry batteries.

Read a whole bunch more on Battery University. Fast charging is a convenience, but it's damaging, for the convenience, the battery's life and reducing it's capacity.

My take away from the above in bold is this.... use your home charging station if at all possible. Not public charging facilities. It's that simple... recharge at home, not in public.

I don’t disagree with any of that. None of that has anything to do with the warranty though.

(Edit: except the charging at home bit. I don't think they care what kind of AC charging so long as its compliant with the J1772 standard)

 

[ultim8gamr]

Reading this thread totally makes me wonder if my car is not performing correctly. 2016 egolf SE with FC option. For the first 20k miles I never had a need to fast charge. Lately (at 23k) I've been taking it on "longer" trips and have found that if I DCFC one day (and charge by L1 or L2 at my destination) it will not DCFC a day later on the way home. Let alone consecutively. It just acts unresponsive with both EVgo or Chargepoint DCFC if I haven't had at least 2 full cycles of AC charging in between if I want to DCFC again.
Anyone else have experience with the fast charge not able to communicate with vehicle? I thought it would default to slower speeds if conditions were not ideal for the battery but I get nothing.

 

[Sparklebeard]

Reading this thread totally makes me wonder if my car is not performing correctly. 2016 egolf SE with FC option. For the first 20k miles I never had a need to fast charge. Lately (at 23k) I've been taking it on "longer" trips and have found that if I DCFC one day (and charge by L1 or L2 at my destination) it will not DCFC a day later on the way home. Let alone consecutively. It just acts unresponsive with both EVgo or Chargepoint DCFC if I haven't had at least 2 full cycles of AC charging in between if I want to DCFC again.
Anyone else have experience with the fast charge not able to communicate with vehicle? I thought it would default to slower speeds if conditions were not ideal for the battery but I get nothing.

That seems unusual. You definitely can DCFC over and over without AC charging, putting aside concerns about what that might do for the battery). Is the 16 SE limited in some way compared with the SEL?

 

[theturtle32]

Just wanted to throw this out there... in researching this topic, I came across this article on VW's own newsroom site, touting the ability to use consecutive DC fast charging to complete a long distance trip in a 2016 e-Golf. That would suggest to me that occasional road-tripping involving consecutive DC fast charge sessions isn't something that is going to void the warranty.

Article Link:
https://newsroom.vw.com/vehicles/road-tripping-from-new-york-to-dc-on-just-electricity/

Brian

 

[f1geek]

Absolutely right. Also, the charging speed (and motor power) will decrease if the pack gets above a certain temperature as determined by the BMS.