verdict: best practice charging % max for battery longevity

[eGopher]

Have 2015 SEL with 43K miles and was delay charging only to 90% up until car-net subscription expired.
Now immediate charging to 100% on a regular basis using level2 EVSE.
Never used DC fast charge.

Will this impact battery longevity?
How can we see current battery capacity without bringing car to dealership?

Any difference in charging strategy for 2015/2016 vs 2017+ ?

Anyone with a high mileage 2017 - What are you seeing?

 

[RonDawg]

You should avoid leaving the car at 100% charge for extended periods of time, especially in hot weather. Right before my CarNet expired, I had set it so that it always charged to 80%, and for the few times I would need 100% I would go out to the garage when charging was done and hit the timer override button.

 

[mfennell]

I went with delayed charging to 90%, assuming hitting the immediate charge button would cause it to charge to 100%. Not so. It does start immediately, then stops at 90%, then it will continue if I start it again.

I haven't charged to 100% in probably two years and thought there might be some pack balancing effect if I charged to 100.

 

[JoulesThief]

The less time the battery sits on a full charge, the better. Avoid DCFC as much as possible, to extend battery life. Your battery never really recharges to 100%, only a Tesla has that capability.

VW has designed the charger pack so that the most level of charge the battery can hold was 22.1 KWh out of a 24.2 kWh battery pack. That's about a 91% charge. VW did this so that the battery will get through the warranty.

The needle on the battery charge gauge has a red zone. Like anything else on a dashboard, that is a gauge, that has red on it, it means STOP! and fix the problem. In this case, the problem is your battery charge is too low, so don't drive the car with the needle in the red zone. Remember, RED means STOP! NOW! and fix the problem. That includes low battery charge, there's a lot of resistance in the battery when the state of charge is so low and you keep depleting it. Resistance creates heat, heat wrecks your battery, so don't go there.

 

[mfennell]

The less time the battery sits on a full charge, the better. Avoid DCFC as much as possible, to extend battery life. Your battery never really recharges to 100%, only a Tesla has that capability.

You repeat that as fact but I've never seen actual data to support it. Do you have a source?

 

[Sparklebeard]

I think it's fair to say that DCFC wears the battery more than AC charging.

I'm not sure what the comment about Teslas being the only EVs to charge to 100? They don't charge to true 100% either... like all EVs, Tesla restricts the very top portion of the battery to protect it.

 

[JoulesThief]

The less time the battery sits on a full charge, the better. Avoid DCFC as much as possible, to extend battery life. Your battery never really recharges to 100%, only a Tesla has that capability.

You repeat that as fact but I've never seen actual data to support it. Do you have a source?

There are 3 sentences there, which one are you looking for data on?

A Lipo battery stores best at 40 to 60% SOC. Anything above or below that shortens the life of the cells in the battery.

Any LiPo battery that is recharged at a less than 1C recharge rate, 1 C being recharged fully in an hour, and less than 1C being recharged at full in less than one hour, is sacrificing convenience and time for long term life of the battery cells.

You'll have to do a search on the Tesla, it has the ability to more fully recharge cells, if you change the settings, but they warn you of what happens to battery life, if you do so.

 

[Sparklebeard]

You'll have to do a search on the Tesla, it has the ability to more fully recharge cells, if you change the settings, but they warn you of what happens to battery life, if you do so.

It's no different to the e-Golf's ability to cap the charge level using the e-Manager/Car-Net, its just Tesla implements it in a nice, straightforward "maximum charge level" setting. 100% in that setting, though, is not 100% true state of charge, much like 100% on the e-Golf is not 100% true SOC.

I have my e-Golf set to only charge up to 70% unless I override it to charge to 90%. That's just what the Tesla does via a more user friendly UI. I did a lot of searching to try to find some additional "above 100%" setting but I don't see anyone saying that you can charge beyond the upper cap and into the top end buffer.

 

[JoulesThief]

You'll have to do a search on the Tesla, it has the ability to more fully recharge cells, if you change the settings, but they warn you of what happens to battery life, if you do so.

It's no different to the e-Golf's ability to cap the charge level using the e-Manager/Car-Net, its just Tesla implements it in a nice, straightforward "maximum charge level" setting. 100% in that setting, though, is not 100% true state of charge, much like 100% on the e-Golf is not 100% true SOC.

I have my e-Golf set to only charge up to 70% unless I override it to charge to 90%. That's just what the Tesla does via a more user friendly UI. I did a lot of searching to try to find some additional "above 100%" setting but I don't see anyone saying that you can charge beyond the upper cap and into the top end buffer.

If you limit each LiPo cell to a maximum of 4.05V per cell, you can extend the life of the battery pack, considerably. Figure out how that's done, and you're at a 90% SOC, as near as I can tell.

 

[mfennell]

Your battery never really recharges to 100%, only a Tesla has that capability.

You repeat that as fact but I've never seen actual data to support it. Do you have a source?

There are 3 sentences there, which one are you looking for data on?

Is there any evidence that the e-golf battery does not charge cells to 4.2v at 100%? I haven't seen it and I've been reading this form as long as you have.

I can't find a link now but Tesla owners have actually measured 4.2V at 100% in the S/X.

 

[f1geek]

I have some evidence:

Yesterday I charged the 2017 e-Golf to 100% immediately prior to a long trip. I plugged in OBDEleven and while car was at "100%" according to the analog gauge (I pressed the immediate charge button and let the car charge until full), OBDEleven said 96% SoC. The pack voltage was 360.8 V, which works out to 360.8/88 = 4.10 V per cell.

 

[mfennell]

I have some evidence:

Yesterday I charged the 2017 e-Golf to 100% immediately prior to a long trip. I plugged in OBDEleven and while car was at "100%" according to the analog gauge (I pressed the immediate charge button and let the car charge until full), OBDEleven said 96% SoC. The pack voltage was 360.8 V, which works out to 360.8/88 = 4.10 V per cell.

Awesome. Thanks! I've been wondering this for ages. So "90%" charging is comfortably in the mid-to-upper 80% range. Maybe not where you want it 24/7 but probably just right for timed charging.

 

[djk]

Is there a way to set 90% for the max charge WITHOUT programming a time-to-be-ready as well? If you select a charging regime which maxes at 90%, and then your CAR-NET subscription runs out, will it continue to use the last regime you set or charge as though none were set (i.e. charge to 100%)? If you DO have a regime set, will the 'immediate' charge button at the receptacle on the car ignore the regime?
Thanks-

 

[Sparklebeard]

Is there a way to set 90% for the max charge WITHOUT programming a time-to-be-ready as well? If you select a charging regime which maxes at 90%, and then your CAR-NET subscription runs out, will it continue to use the last regime you set or charge as though none were set (i.e. charge to 100%)? If you DO have a regime set, will the 'immediate' charge button at the receptacle on the car ignore the regime?
Thanks-

The only way is to have a timer set.

I do it by having a timer set to 90% at 3:30pm on Friday, with a minimum charge level set to 70%.

That means that any time I plug in at work it automatically charges to 70% and stops. On Friday afternoons it will then continue to 90% by 3:30pm. I could just set that timer to 70% also and the car would never charge above 70%, unless I hit the "Charge now" button, which always overrides the timer and charges immediately to 100%.

if you let Car-Net lapse, all your programmed timers will stay set forever and keep working the same way.

 

[RonDawg]

Is there a way to set 90% for the max charge WITHOUT programming a time-to-be-ready as well?

Yes. Set the "Minimum Charge Level" to 90%. It will always charge to 90% the moment you plug in.

If you select a charging regime which maxes at 90%, and then your CAR-NET subscription runs out, will it continue to use the last regime you set or charge as though none were set (i.e. charge to 100%)?

Yes.

If you DO have a regime set, will the 'immediate' charge button at the receptacle on the car ignore the regime?
Thanks-

Yes and no. My minimum charge level is at 80%. I find that if the car is less than 80%, even if I press the immediate charge button, the car will often stop at 80%. So I wait until it stops at 80% then go out to the car and hit the immediate charge button again. Fortunately to get to 100% takes only about an hour or so.