Charging speed and degradation

[egolfEr]

I have a new 2019 eGolf SE with a juicebox pro 40. With this combination I am able to charge at the following speeds:

1. 6 Amps
2. 12 Amps
3. 16 Amps
4. 24 Amps
5. 32 Amps
6. 40 Amps

Upto what speeds do people feel it is safe to charge without degrading the battery?

 

[RonDawg]

It's known that the faster you charge, the more heat you generate, and heat kills Lithium batteries. However you have to balance that with your personal requirements, and of course the capacity of your electrical panel.

Your eGolf won't accept anything more than 7.2 kW which is 30 amps @ 240 volts, so 40 amps isn't necessary unless you have a Tesla that is also going to charge up. If it's sufficient for your needs, I'd even drop down to 24 amps. Basically, will it be sufficient to recharge my car to the desired battery level overnight, and/or within any off-peak rate time period?

I have a Clipper Creek LCS-25 which only supplies 20 amps. When I had a 2012 Leaf with its 16 amp on-board charger, it was overkill, but with my 30 amp eGolf it doesn't charge at the fastest L2 speed. But in reality, I plug in every day and charge to 80%, and the car stops charging about 60-90 minutes later. So I feel no need to upgrade to a faster unit (plus I am limited to a 30 amp circuit anyway, so 24 amps is the most I can go with).

I should say that for anything less than DCFC speeds, keeping the battery at/near full when it's hot outside will do more to degrade your battery.

 

[miimura]

AC charging of any kind won't do anything detrimental to the battery. The only concerns come up when you start talking about DC Fast Charge.

 

[f1geek]

High power AC charging at high ambient temps when the battery pack is already hot from a long trip can absolutely, permanently damage the battery. We don’t drive Teslas that have active liquid cooled battery packs. If you want the e-Golf pack to degrade less, charge as slowly as fits your needs.

 

[JoulesThief]

High power AC charging at high ambient temps when the battery pack is already hot from a long trip can absolutely, permanently damage the battery. We don’t drive Teslas that have active liquid cooled battery packs. If you want the e-Golf pack to degrade less, charge as slowly as fits your needs.

Define "High power AC charging". Also define high ambient temperatures. I don't think level 2 240V AC charging at 30 amps hurts anything. As long as I've been working with LiPo batteries, as long as it took over an hour to reach a full recharge of a LiPo battery pack, it was never considered high power. Since with a 2017 on e-Golf with the 35.6 kWh battery pack, it takes about 4 to 4.5 hours to charge with a 240V package, vs a 208 volt commercial transformer supplied public charger, which will take 5 to 5.5 hours, I don't understand what you're talking about.

Now if you mean High Power Direct Curret or DC charging, that's another matter. I wouldn't worry at all about the Charge Point DC100 EVSE DCFC units rated at up to 24 kWh, because most of them that I've used can barely show 21.5 kwh when charging and usually under 20kWh. So they are pretty non impactful, even with the 2015 and 2016 VW battery packs here in the USA.

It's the 55 kWh DC fast chargers that will get you charged to 80% in under 60 minutes that are problematic with the current versions of e-Golf battery packs.

 

[f1geek]

7.2 kW is high power charging when the temperatures are high and the pack is already hot. High ambient temperatures are temperature you find in the central valley of CA or New Mexico or Arizona, etc. routinely in summer (above 40 C). The e-Golf battery pack weighs hundreds of kilograms and can retain heat very well due to its large mass. Remember, joule heating is a function of the square of the current. Yes, DC charging delivers more current than AC charging, but if the pack is already at 40 C, charging fast (even AC charging) will raise the temperature more and do damage.


There is no such thing as a 240V package - all e-Golfs are able to charge at 240V in the USA. There is no such thing as a charging station rated at 24 kWh, 21.5 kWh, 20 kWh, or 55 kWh. kWh is energy. Charging stations are rated in kW. If you are looking how many kWh you put into the battery, as long as you push it in slowly when it's hot, then the damage will be reduced, thus it is imperative to charge more slowly when it's hot IF you want your pack to last with the least amount of degradation. I'm sure the battery pack will last for the warranty period and not have more than 30% degradation, but I want my pack to last twice the warranty period with less than 30% degradation. Unlike JT, I don't have money to burn on a new car when the pack is unusable, so I will treat the battery like it is fine crystal and handle with extreme care so that I am able to get 200,000 miles of use out of and still have minimal degradation.

 

[JoulesThief]

7.2 kW is high power charging when the temperatures are high and the pack is already hot. High ambient temperatures are temperature you find in the central valley of CA or New Mexico or Arizona, etc. routinely in summer (above 40 C). The e-Golf battery pack weighs hundreds of kilograms and can retain heat very well due to its large mass. Remember, joule heating is a function of the square of the current. Yes, DC charging delivers more current than AC charging, but if the pack is already at 40 C, charging fast (even AC charging) will raise the temperature more and do damage.


There is no such thing as a 240V package - all e-Golfs are able to charge at 240V in the USA. There is no such thing as a charging station rated at 24 kWh, 21.5 kWh, 20 kWh, or 55 kWh. kWh is energy. Charging stations are rated in kW. If you are looking how many kWh you put into the battery, as long as you push it in slowly when it's hot, then the damage will be reduced, thus it is imperative to charge more slowly when it's hot IF you want your pack to last with the least amount of degradation. I'm sure the battery pack will last for the warranty period and not have more than 30% degradation, but I want my pack to last twice the warranty period with less than 30% degradation. Unlike JT, I don't have money to burn on a new car when the pack is unusable, so I will treat the battery like it is fine crystal and handle with extreme care so that I am able to get 200,000 miles of use out of and still have minimal degradation.

If this is your first VW, you'll find out that by 10 years, a lot of the car that's got plastic parts will start falling apart. Least of your worries will be the battery pack. You'll probably be looking to replace it with something that doesn't break or have failures. VW designs for 150k miles. They don't support car models over 10 years in age.

 

[Slaphappygamer]

Your eGolf won't accept anything more than 7.2 kW which is 30 amps @ 240 volts, so 40 amps isn't necessary unless you have a Tesla that is also going to charge up

Good tip. I have a 60amp fuse in my 220 circuit currently. Would the golf “ignore” the extra amperage? Or will the extra amperage be bad in the long run?

 

[Sparklebeard]

Your eGolf won't accept anything more than 7.2 kW which is 30 amps @ 240 volts, so 40 amps isn't necessary unless you have a Tesla that is also going to charge up

Good tip. I have a 60amp fuse in my 220 circuit currently. Would the golf “ignore” the extra amperage? Or will the extra amperage be bad in the long run?

Easiest way to think of it:

Voltage is the ‘pusher’ of the energy.
If your outlet is X Volts, the device plugged in must handle that voltage or it will damage the device.

Amps are the ‘capacity’ of the circuit.
The devices plugged into that circuit will ‘pull’ a certain number of amps. If your breaker is Y Amps, then that sum total of devices on that circuit must never be pulling more than Y amps* or they can damage the circuit (in reality this should trip the breaker before any damage can occur to the wiring in the house).

(* to be specific, they can’t continuously pull more 80% of Y Amps, i.e. a 30A breaker supports a 24A device. I believe this is to allow some headroom for brief spikes without tripping a breaker)

So if you have a 240 V circuit with a 60A breaker, you must ensure that the vehicle supports 240V (which it does), and that it will not exceed 0.80*60A=48A (e-Golf draws ~30A)

 

[wohlford]

I have a question that I think is in a similar vein..

I am looking to get a jukebox pro 32 for my 20126 golf...
What is the difference if I have 30A breaker (with 24a to the vehicle) vs. 40A breaker (with 32A to the vehicle)?

Is the time to charge that much quicker?

 

[f1geek]

If your e-Golf has an on-board charger that operates at 30 amps (I believe the 2016 base model has a 3.6 kW (15 amps) charger and optioned with the DCFC package has the 7.2 kW charger), then anything providing at least 30 amps is fine. The on-board charger determines the maximum AC amps the car will accept. You can connect the car to a 60 amp AC charging station, too, but the car will only accept the on board's charger maximum rated current.

Charging speed (power) = Volts x amps

240 V x 30 amps = 7.2 kW

240 V x 24 amps = 5.8 kW

240 V x 15 amps = 3.6 kW (If your car only accepts 15 amps, then this is the speed you will get with either charging station)

Assuming you need to charge ~70% of the pack (15 kWh):

15/7.2 = 2.1 hours
15/5.8 = 2.6 hours
15/3.6 = 4.2 hours