How bad is DC charging ?

[YeGolf]

I have 61 mi daily commute.
In most cases I need to charge my car (eGolf 2017) every second day.

Of course more convenient will be charging on DC charger. But how really bad is it.
Did somebody here been charging car mostly on DC?

I read some articles about charging Nissan Leaf on DC and AC chargers. And battery that was charged with DC lost about 2-3% more capacity after 63000 miles. For me it's seems not so bad.

Also what will be better for buttery daily charging on DC and keep the battery charged in (25%-75%) or every second day with AC and (15%-95%).

 

[f1geek]

To pamper your battery, if you keep it charged in the range of 30% to 70% SOC, you will get the longest possible lifespan. The benefit you get from keeping the SOC in this range outweighs any increased cycling related degradation if you need to charge once a day vs every two days. You can look at Battery University or peer reviewed papers and you will find that keeping battery in the sweet spot SOC range dramatically decreases effect of cycling on rate of degradation. Avoid DC charging if you can so that excess heat is not generated in the pack. High temps are not good for the pack, especially if it has no active thermal management (e-Golf has no active thermal management). Additionally, if are going to charge every day, try to limit amperage to 13 amps (via e-Manager) so that battery stays cool during charging. Also, use delayed charging so that battery has time to cool prior to charging. If you read the 2018 Leaf user's manual, you will see all the precautions that Nissan recommends to extend the life of the battery - all of these precautions apply to the e-Golf, BUT VW was smart enough to let us choose max % SOC (Leaf does not offer this feature) which will be especially helpful during hot summer days.

 

[YeGolf]

To pamper your battery, if you keep it charged in the range of 30% to 70% SOC, you will get the longest possible lifespan. The benefit you get from keeping the SOC in this range outweighs any increased cycling related degradation if you need to charge once a day vs every two days. You can look at Battery University or peer reviewed papers and you will find that keeping battery in the sweet spot SOC range dramatically decreases effect of cycling on rate of degradation. Avoid DC charging if you can so that excess heat is not generated in the pack. High temps are not good for the pack, especially if it has no active thermal management (e-Golf has no active thermal management). Additionally, if are going to charge every day, try to limit amperage to 13 amps (via e-Manager) so that battery stays cool during charging. Also, use delayed charging so that battery has time to cool prior to charging. If you read the 2018 Leaf user's manual, you will see all the precautions that Nissan recommends to extend the life of the battery - all of these precautions apply to the e-Golf, BUT VW was smart enough to let us choose max % SOC (Leaf does not offer this feature) which will be especially helpful during hot summer days.

Thank you.
But from the other side if the battery will lose more than 30%, there is possibility to get new battery.

 

[f1geek]

From the data I've seen on the 24.2 kWh battery degradation, I suspect that the VW engineers did a good job designing the pack (with Panasonic, who knows Lithium Ion batteries in EVs, based on their depth of experience with Tesla and others) and if you treat the pack according to the e-Golf manual, you may see less than 30% degradation at the end 8 years. Then again, every car will be treated differently by different owners, and I'm guessing the local climate also has an impact of battery longevity, too. The manual instructs you to alternate a DC charge with AC charge, so if you decide to DC charge once a day with no AC, you will have ignored VWs directive. Also, if you DC charge "frequently and consecutively", you will be ignoring another VW directive. You probably should read the manual very carefully and strongly consider adhering to it if you expect to have warranty coverage, as per the wording the high voltage battery warranty booklet.

I own my 2017 e-Golf LE and would prefer to have a battery with minimal degradation at the end of 10 or 15 years. As I use it primarily for local commuting, I will attempt to pamper it as much as possible to lengthen its usable lifetime with a high state of health.

 

[YeGolf]

From the data I've seen on the 24.2 kWh battery degradation, I suspect that the VW engineers did a good job designing the pack (with Panasonic, who knows Lithium Ion batteries in EVs, based on their depth of experience with Tesla and others) and if you treat the pack according to the e-Golf manual, you may see less than 30% degradation at the end 8 years. Then again, every car will be treated differently by different owners, and I'm guessing the local climate also has an impact of battery longevity, too. The manual instructs you to alternate a DC charge with AC charge, so if you decide to DC charge once a day with no AC, you will have ignored VWs directive. Also, if you DC charge "frequently and consecutively", you will be ignoring another VW directive. You probably should read the manual very carefully and strongly consider adhering to it if you expect to have warranty coverage, as per the wording the high voltage battery warranty booklet.

I own my 2017 e-Golf LE and would prefer to have a battery with minimal degradation at the end of 10 or 15 years. As I use it primarily for local commuting, I will attempt to pamper it as much as possible to lengthen its usable lifetime with a high state of health.

Thanks. You are absolutely right. I will try to avoid DC chargers as much as possible, to keep the battery in good condition.

 

[Kosta]

From the data I've seen on the 24.2 kWh battery degradation, I suspect that the VW engineers did a good job designing the pack (with Panasonic, who knows Lithium Ion batteries in EVs, based on their depth of experience with Tesla and others) and if you treat the pack according to the e-Golf manual, you may see less than 30% degradation at the end 8 years. Then again, every car will be treated differently by different owners, and I'm guessing the local climate also has an impact of battery longevity, too. The manual instructs you to alternate a DC charge with AC charge, so if you decide to DC charge once a day with no AC, you will have ignored VWs directive. Also, if you DC charge "frequently and consecutively", you will be ignoring another VW directive. You probably should read the manual very carefully and strongly consider adhering to it if you expect to have warranty coverage, as per the wording the high voltage battery warranty booklet.

I own my 2017 e-Golf LE and would prefer to have a battery with minimal degradation at the end of 10 or 15 years. As I use it primarily for local commuting, I will attempt to pamper it as much as possible to lengthen its usable lifetime with a high state of health.

Thanks. You are absolutely right. I will try to avoid DC chargers as much as possible, to keep the battery in good condition.

I heard the heat generated by DC charge is the enemy - time to dissipate the heat is essential - that was why back to back charges ( under ? 4 hrs ) in between charging is not enough time for the battery to cool down unless your in Norway ;-)

 

[f1geek]

It's not the heat, per se, but the high temperatures caused by internal battery resistance, that are damaging to the pack. For cars with TMS (thermal management system), the heat is removed QUICKLY and thus the battery temp remains within a controlled range. Even in Norway, repeated DC fast sessions can lead to very high battery temperatures in a battery pack with no TMS- just watch Bjorn Nyland on YouTube beat up a 2018 Leaf battery pack in winter in Norway and you'll see that even freezing temperatures don't allow the battery pack to cool quickly enough to keep the temperatures in check. While the edges of the pack may be cool, the interior remains very hot and is slow to cool through passive heat transfer. VW apparently designed the pack and car in such a way that the heat is conducted away from the cells and into the car's frame (and then the air), but still there is no comparison between the rate of heat loss by passive (conduction and radiation) means vs by active (direct contact fluid mediated heat transfer) means.

If you are driving at an average speed to 60 mpH, then back to back charges would occur within 2 hours in a 2017 e-Golf, so there is very little time for the heat to dissipate, though based on my experience, the e-Golf 24.2 kWh pack does not heat up as fast as the Leaf. I'll have to run a test to see how the 35.8 kWh pack performs.

 

[YeGolf]

But what if I'll charge ... lets say for a 25 min from 30% and up to 80%.
Does it heart the battery as will ? I thing there won't be much heat during this short period of time.

Yesterday I was charging on J1772 almost 7kwh - and after 4 hours I touched the battery body and it was cold.

 

[2016golfse]

My thoughts, and they're purely speculative, nothing more:

1) DC charging is worse for the 2017's and than 2015/2016. You can't increase energy storage by 50% in the same physical space without compromising heat dissipation.
2) Battery longevity (assuming Level 1 and 2 charging) is easier to maintain for 2017 versus 2015/2016 since the increased energy storage reduces the depth of discharge and it's easier to maintain a state of charge between 50-80%.
3) I have a bit better confidence in the Panasonic batteries in the 2015/2016 than the Samsung batteries in the 2017's, because (a) passive cooling with Panasonic batteries has been around since the 2012 Prius Plug In, (b) more long term experience with Panasonic's chemistry, albeit in Tesla's active cooling application, and (c) I'm not aware of any other Samsung equipped EV with passive cooling.

 

[f1geek]

Touching the pack outside only measures the external pack shell temperature, which will be at the ambient temperature. You need to get an OBD reader like OBDEleven and get a reading from temperature sensors deep within the pack.

Yes, charging from 30% to 80% using DCFC, say at 43 kW, will significantly heat up the battery pack, as compared to using AC at 7.2 kW or less.

Good point about Panasonic vs Samsung SDI. We'll have to how the 2017 pack fares. I plan to only charge the pack to 80% in the winter and 70% in the summer, so I hope to extend its life. On the rare 100 mile or greater trips I take, I will then charge to 100% immediately prior to leaving so the pack spends very little time at high voltage.

 

[JoulesThief]

. On the rare 100 mile or greater trips I take, I will then charge to 100% immediately prior to leaving so the pack spends very little time at high voltage.

/\ This... is good battery management.

 

[YeGolf]

Yesterday I fully charged battery at 12:30am
In the morning at 8 am I recognized that almost 1 bar (1/16) is gone. How is it possible ?

Another thing.
If I charge up to 100% right before using it. If should be ok for the battery?

 

[f1geek]

The "loss" in SOC could be due to temperature. What was the ambient temperature at 12:30 am and 8 am? I have noticed I get more range once the battery pack warms up to around 20 to 30 C. Was it warmer at 8 am than it was at 12:30am? Otherwise, I don't think it's a big deal and probably not indicative of any problems.

Yes, for battery longevity, charge up to 100% immediately before using. If you know you need 100% at 8am, I would suggest using the charge timer to have the battery hit 100% at 7:30 am to 7:45 am so that the battery spends the least amount of time at full charge.

 

[YeGolf]

The "loss" in SOC could be due to temperature. What was the ambient temperature at 12:30 am and 8 am? I have noticed I get more range once the battery pack warms up to around 20 to 30 C. Was it warmer at 8 am than it was at 12:30am? Otherwise, I don't think it's a big deal and probably not indicative of any problems.

I was thinking about difference in temperature too.The temperature at 12:30am was about 10F higher than at 8 am.

Yes, for battery longevity, charge up to 100% immediately before using. If you know you need 100% at 8am, I would suggest using the charge timer to have the battery hit 100% at 7:30 am to 7:45 am so that the battery spends the least amount of time at full charge.

I wish I could do it. I live in apartment. But looks like if I will charge at night up to 90-100% the difference in temperature will lower the SoC.

 

[YeGolf]

So. If the only heat is damaging battery then 10-20 min charging on DC should be OK or not ?

Also I checked the charging speed, during the first time I was charging with DC and it shows
from the beginning - 14 min of charging === 39 kw
14 min - 19 min === 38 kw
19 min - 24 min === 35 kw
24 min - 29 min === 28 kw
29 min - 34 min === 20 kw
I think the speed start decreasing because of heat. Maybe the fist 20 min is not damaging the battery.

The second thing about AC charging. Is it batter to charge on 3.3 kw or 6.6 kw or higher. Or maybe even from 110 outlets. Or all these cases are the same for battery ?

 

[JoulesThief]

So. If the only heat is damaging battery then 10-20 min charging on DC should be OK or not ?

Also I checked the charging speed, during the first time I was charging with DC and it shows
from the beginning - 14 min of charging === 39 kw
14 min - 19 min === 38 kw
19 min - 24 min === 35 kw
24 min - 29 min === 28 kw
29 min - 34 min === 20 kw
I think the speed start decreasing because of heat. Maybe the fist 20 min is not damaging the battery.

The second thing about AC charging. Is it batter to charge on 3.3 kw or 6.6 kw or higher. Or maybe even from 110 outlets. Or all these cases are the same for battery ?

Read your owners manual.

VW recommends recharging at night at home, and to use DC fast charging "sparingly".

Any time you exceed a 1C charge rate on any lithium ion battery chemistry, you are doing damage to the battery, by recharging it too fast.
That basically means recharging to full capacity in an hour or mores worth of time is considered "acceptable". Charging to full capacity in less than an hour exceeds the charging rate of the battery, for the sake of convenience, and does long term damage internally to the battery. It's done only for time convenience, but like your smart phone battery, it shortens the life of the battery capacity, permanently. That means less range traveled between recharges.

Avoid fast charging, if you're interested in longevity of your battery and keeping it's range maximized for the life of the car battery. That's just the way it goes with an entry level electric car with a passively cooled battery. Compromise in engineering and cost cutting designs to meet a lower price point. You want to fast recharge, buy a BMW i3 or a Tesla.

 

[f1geek]

The manual says to avoid “frequent and consecutive” DCFC sessions. It also says to follow a DC session with an AC session. The charge rates you observed are normal and not due to high pack temperature. The charging speed is a function of pack SOC and pack temperature. As long as the pack temperature is not high, the car will charge at the maximum available speed (determined by the amps delivered by the DC charger and the pack voltage) until the SOC gets to about 85%, at which point the rate slows to protect the battery. All lithium ion battery charging systems work this way-watch your smartphone charge and you’ll see the same type of behavior.

For AC, a slower rate will generate less heat in the pack and keep it cooler. I charge at 3.1 kW since I have time to allow slow charging. I would recommend charging with 240V if you can as I believe the on board charger is more efficient at that voltage vs 120 V.

 

[JoulesThief]

So. If the only heat is damaging battery then 10-20 min charging on DC should be OK or not ?

Also I checked the charging speed, during the first time I was charging with DC and it shows
from the beginning - 14 min of charging === 39 kw
14 min - 19 min === 38 kw
19 min - 24 min === 35 kw
24 min - 29 min === 28 kw
29 min - 34 min === 20 kw
I think the speed start decreasing because of heat. Maybe the fist 20 min is not damaging the battery.

The second thing about AC charging. Is it batter to charge on 3.3 kw or 6.6 kw or higher. Or maybe even from 110 outlets. Or all these cases are the same for battery ?

The DC charging rate and taper rate is relative to several conditions. What was state of discharge how many Kw were still stored in the battery when you started charging. If the battery was discharged and cool due to city stop and go driving, versus driving 70 + mph on the freeway and immediately getting off the freeway to fast charge, which will lead to a slower fast charge rate. How hot was the battery, due to previous driving conditions when you started charging.
A cool battery that is just barely in the red on the fuel gauge will take 39 to 40 kWh for perhaps 30 or 35 minutes, before starting to taper off, taking on 20 to 22 kwh. But from there, things will slow down quite a bit in the next 15 to 20 minutes, on a 55 kWh capable DC FC. This is for a 35.8 kWh battery with about 32 useable kWh.