80% or 100% Re: Charging the battery

[keithr]

This is all based on the assumption that 100% is 100%.

No, it's based on the car's indicated 100% and 0%. If the battery management system didn't prevent the user from using the top and bottom ~5% then there would be a lot more failing battery packs!

it also means that you can have regen available even when the car indicates 100% charge.

No it doesn't, because the BMS won't let you charge to more than 100% indicated charge. So at an indicated 100% SOC there will be no regen available. That's another reason why I like single pedal driving, because the response to backing off the accelerator pedal is always the same - if less regen is available then it uses the brakes to give the same consistent level of retardation. Hence on page 575 of the Owner's Manual (in the Maximum Charge Setting section) it states:

"If the charge station is located up on a hill, you do not need to fully charge the vehicle at the station. This is because additional electrical energy can be stored in the High Voltage battery as the motor acts an electric generator while going down a hill", i.e if you do charge to 100% then you won't be able to take advantage of regenerative braking when driving away downhill.

The Nissan LEAF (once again) did it better in that it's console display would show how much regen was available, and it clearly was none at 100% SOC and gradually increased as the SOC went down. Full regen wasn't avalable until around 80% SOC, if I recall correctly. (It would also show less than max regen available during cold weather - charging too fast when the battery is cold can also damage the battery, and max regen in the LEAF was 30kW.)

[Reuben80]

This is all based on the assumption that 100% is 100%.

No, it's based on the car's indicated 100% and 0%. If the battery management system didn't prevent the user from using the top and bottom ~5% then there would be a lot more failing battery packs!

it also means that you can have regen available even when the car indicates 100% charge.

No it doesn't, because the BMS won't let you charge to more than 100% indicated charge. So at an indicated 100% SOC there will be no regen available. That's another reason why I like single pedal driving, because the response to backing off the accelerator pedal is always the same - if less regen is available then it uses the brakes to give the same consistent level of retardation. Hence on page 575 of the Owner's Manual (in the Maximum Charge Setting section) it states:

"If the charge station is located up on a hill, you do not need to fully charge the vehicle at the station. This is because additional electrical energy can be stored in the High Voltage battery as the motor acts an electric generator while going down a hill", i.e if you do charge to 100% then you won't be able to take advantage of regenerative braking when driving away downhill.

The Nissan LEAF (once again) did it better in that it's console display would show how much regen was available, and it clearly was none at 100% SOC and gradually increased as the SOC went down. Full regen wasn't avalable until around 80% SOC, if I recall correctly. (It would also show less than max regen available during cold weather - charging too fast when the battery is cold can also damage the battery, and max regen in the LEAF was 30kW.)

If there was no regen in the leaf at 80% it shows you how much important it is the keep the charge under 80% as the BMS will be refusing to charge it more. I don't really think that it was 80% though as I see it it is too low. It would be good to try this experiment on the e and see till what percentage it will not regen to the full potential.

[rickwookie]

This is all based on the assumption that 100% is 100%.

No, it's based on the car's indicated 100% and 0%. If the battery management system didn't prevent the user from using the top and bottom ~5% then there would be a lot more failing battery packs!

No, because in this case it's not just the top and bottom 5%. Honda are reserving a total of 20%, suggesting that when the car indicates to the user that it is 100% charged, it may well still be 10-15% bellow fully charged wrt the total battery capacity.

it also means that you can have regen available even when the car indicates 100% charge.

No it doesn't, because the BMS won't let you charge to more than 100% indicated charge. So at an indicated 100% SOC there will be no regen available. That's another reason why I like single pedal driving, because the response to backing off the accelerator pedal is always the same - if less regen is available then it uses the brakes to give the same consistent level of retardation. Hence on page 575 of the Owner's Manual (in the Maximum Charge Setting section) it states:

"If the charge station is located up on a hill, you do not need to fully charge the vehicle at the station. This is because additional electrical energy can be stored in the High Voltage battery as the motor acts an electric generator while going down a hill", i.e if you do charge to 100% then you won't be able to take advantage of regenerative braking when driving away downhill.

Yes, the bit in quotes there is from the manual - the second part is pure hypothesis on your part.

[rickwookie]

It would be good to try this experiment on the e and see till what percentage it will not regen to the full potential.

Indeed. Has anyone on here experienced the e refusing to regen, or indicating that is is not able to regen fully and any particular SoC?

Ab little OT but in my limited (so far) experience, the e's regen is weak as piss anyway - e.g. coming off a motorway on an uphill slip-road and using the left paddle to set regen at four chevrons (or whatever the setting is) and the car hardly feels like its pushing back on the motor particularly hard. I still had to use plenty of left peddle.

[SwissChris]

Well are you using one pedal driving? However it does not matter anyway, as the Honda e is pretty intelligent. Even if you press the break pedal, the battery gets recharged. Only if you press hard enough, the physical brakes come into play. You can see it on the left part of the center display (recharge in green).

[keithr]

If there was no regen in the leaf at 80% it shows you how much important it is the keep the charge under 80% as the BMS will be refusing to charge it more.

You misread what I wrote. I said full regen was available at 80% SOC (and lower), not that no regen was available at 80% SOC. Charging to 80% instead of 100% would potentially be more economical because you would always have full regen available, whereas less that full regen is available to start with if you charge to 100%. However, you would still get more range when charging to 100%, obviously. Hence the advice to only charge to 100% if you need the range, because it's better for economy to only charge to 80%, and if you need the range then charge to 100% just before you start the journey because that results in less degradation of the battery.

[Isow]

If there was no regen in the leaf at 80% it shows you how much important it is the keep the charge under 80% as the BMS will be refusing to charge it more.

You misread what I wrote. I said full regen was available at 80% SOC (and lower), not that no regen was available at 80% SOC. Charging to 80% instead of 100% would potentially be more economical because you would always have full regen available, whereas less that full regen is available to start with if you charge to 100%. However, you would still get more range when charging to 100%, obviously. Hence the advice to only charge to 100% if you need the range, because it's better for economy to only charge to 80%, and if you need the range then charge to 100% just before you start the journey because that results in less degradation of the battery.

I might be getting confused here, but I cannot understand why one can’t charge to 100% routinely.
If 100% on a Honda e is actually 80% why will the battery degrade if you charge to 100% ?
Surely that’s Honda’s way of protecting the life of the battery.

[keithr]

Honda are reserving a total of 20%

Nobody knows for sure because Honda has not told us. Some of us have worked out that around 12% is reserved, based on the data displayed by the car. That may or may not be split evenly at the top and bottom charge levels. So usable battery might be between 6 and 94% of actual battery capacity - it's a bit of a guess.

Yes, the bit in quotes there is from the manual - the second part is pure hypothesis on your part.

And, as stated, my experience of driving Nissan LEAFs, which not only display the level of regen that is available but also in normal drive mode (not single pedal mode) you could feel there was virtually no regen braking when the battery was near 100% SOC, compared with the higher strength regen at lower states of charge. In single pedal mode (e-pedal) you could also tell from the display that it was using brakes rather than regen at high battery charge. You could also see that now and again when slowing using regen down a steep hill that it would decide to stop using regen and use the brakes instead, which it would do now and again as a preventative measure to reduce the likelihood that the brake calipers would seize (as brakes are used less often and less strongly in an electric car).

If the BMS prevents the battery charger from exceeding 100% SOC (indicated 100%), then it is logical that it would also prevent regen from exceeding 100% too. The charge rate at near 100% SOC is also much reduced, and likewise regen levels would be at a reduced level too when near 100% SOC; it wouldn't allow you to pump 30kW (the maximum level of regen in a LEAF) into the battery pack when it's 100% charged.

[Isow]

Maybe we can convince Honda to create a button like i3 has.
A button that BMW advises to use only when really necessary, a button that gives you all battery capacity available.
For the e that would give you roughly up to 20% more, the 2 or 3 times a year when you go visit relatives far away or other fun stuff thats outside the e's normal range.

Well, “all” capacity would actually be 25% more, but I would rather Honda configured it so that we had 90% of the battery capacity usable which would give us 12.5% more range all the time (and still give reasonable battery protection. A 20% buffer that Honda has opted for is more than any other EV as far as I am aware, and seems ott. I don't think manufacturers should be allowed to advertise a car as having a 35.5 kWh battery and then employ such a conservative battery cap.

So, charging to 100% wouldn’t degrade the battery because it’s actually 75-80% ?
That’s simply the question.
Thanks

[keithr]

I might be getting confused here, but I cannot understand why one can’t charge to 100% routinely.

You can routinely charge to 100%. It's just less degrading on the battery to not leave the car sat at 100% for long periods.

If 100% on a Honda e is actually 80% why will the battery degrade if you charge to 100% ?
Surely that’s Honda’s way of protecting the life of the battery.

Yes, all manufacturers of electric vehicles program the battery managment systems to not allow you to charge to actual 100%, in order to make the battery last longer than it otherwise would. And they all advise not to leave the vehicle at 100% state of charge for long periods, as that will degrade the battery more quickly. The battery pack will last many years (the original Nissan LEAFs are coming up to 10 years old now, and most are still using their original battery packs), but the batteries degrade over time (more rapidly to start wilth, then it tails off), so that after many years the amount of charge it can hold (and therefore the vehicle's range) will have reduced. Not leaving your battery pack at 100% for long periods will help to reduce the level of degradation, but it might only make a small difference anyway, so you probably shouldn't worry about it too much, but it makes sense to take simple measures to reduce the degradation if you can. As I mentioned, leaving the car at low levels of charge is probably more damaging.