Will Regen Mode Kill the Battery Quicker?

[reeler]

When the Leaf is in regen mode, it pushes kinetic energy back into the battery. LIon batteries have a finite number of cycles that will degrade performance. It stands to reason that constantly drawing energy and putting it back into the battery will accelerate degradation of the battery. Should Normal-mode be chosen over Eco- or B- modes if you want longer battery life?

Discuss . . .

 

[abasile]

I don't see how the use of regen increases total battery cycles. Every kWh of energy put back into the pack via regen is a kWh that won't need to be added from the wall, via L1/L2/QC.

There is likely some additional wear on the battery from the higher power levels typical of regen as well as from the consequent pack heating, though not as much as from QC sessions which tend to sustain even higher power levels. On my long, almost-daily mountain descents, my LEAF sometimes gains a temperature bar from the regen.

Overall, I suspect that the use of regen is a minor factor in battery life compared to the influence of ambient temperature. Much of my LEAF's battery degradation to date probably comes from time spent parked in the heat down the mountain at relatively high SOCs (needed to climb the mountain later). While I can't say for sure, I will say that my LEAF's overall degradation isn't that bad for a two year old car with 32K miles.

 

[Den]

LIon batteries have a finite number of cycles

It means: Full cycles.

If you recharge 1 kWh out of 20 and then use it, it is not a full cycle - just 1/20 of it.

 

[Nubo]

The car restricts regen at higher SOC, or if too cold, etc... And when full regen is available, it tops out at about a 2C charge rate, which is well within the capability of the cells, and typically only lasts a brief time. I did manage to add a couple of bars while slowly descending a mountain but even that was not at full regen the whole time.

 

[edatoakrun]

When the Leaf is in regen mode, it pushes kinetic energy back into the battery. LIon batteries have a finite number of cycles that will degrade performance. It stands to reason that constantly drawing energy and putting it back into the battery will accelerate degradation of the battery. Should Normal-mode be chosen over Eco- or B- modes if you want longer battery life?

Discuss . . .

There is no evidence, IMO, that fast charging either through the DC port or by using regen significantly reduces battery life, other than the effect from each of increasing the battery pack temperature more than slower AC charging does.

Charging through regen will increase charge cycles on your battery just like grid charging, so it probably will reduce battery life proportionally.

I live in a mountainous area, and get close to 20% of my kWh from regen. So, I would expect my LEAF with ~16,000 miles has experienced proportionately more loss of capacity due to the increased battery charge cycling, than for a LEAF that has changed less by regen.

Use the Carwings "rate simulation" page if you want to look up your own regen charging.

For example, last October, CW reported I used ~122.6 kWh from the grid, and ~25.9 kWh from regen, for the month, and each "trip" (start/stop cycle) is individually accounted for in the logs above the total at the bottom of the screenshot below.

I need to add that I I believe my LEAF has some error in its kWh use reports, which shows up not only on CW, but also on my dash and nav screen. And the ~2.5 % under report error in miles driven as reported by CW, means that each CW m/kWh report is precisely mirrored in my dash m/kWh reports, which shows both errors, both in the miles and in (suspected) kWh use.

But the relative proportions of regen to grid kWh use seem to be correct, whether each nominal "kWh" contained 1,000 Wh last October, or somewhere in the ~1,050 to ~1,100 Wh range, which I now believe is more likely.

 

[Deleted member 3147]

LIon batteries have a finite number of cycles

It means: Full cycles.

If you recharge 1 kWh out of 20 and then use it, it is not a full cycle - just 1/20 of it.

Actually, less that that. AFAIK, in general, four 1/4 charge cycles is much less stressful than one full cycle.

 

[DeaneG]

Actually, less that that. AFAIK, in general, four 1/4 charge cycles is much less stressful than one full cycle.

Which is exactly why you want regen - by the time you get home, you'll have used the battery less deeply than if you just used friction braking.

 

[edatoakrun]

LIon batteries have a finite number of cycles

It means: Full cycles.

If you recharge 1 kWh out of 20 and then use it, it is not a full cycle - just 1/20 of it.

Actually, less that that. AFAIK, in general, four 1/4 charge cycles is much less stressful than one full cycle.

IMO:

If you charge from ~50% to ~75% and discharge the same amount four times, almost certainly less "stressful" than one "100%" charge and discharge, even when followed by an immediate recharge.

If you discharge from ~"100%" to ~75% and recharge the same amount four times, and have also left your battery at that "100%" SOC for extended periods of time, probably more "stressful" than one "100%" charge and full discharge, followed my an immediate recharge.

DeaneG

DoxyLover wrote:

Actually, less that that. AFAIK, in general, four 1/4 charge cycles is much less stressful than one full cycle.

Which is exactly why you want regen - by the time you get home, you'll have used the battery less deeply than if you just used friction braking.

In virtually all cases, yes.

You will also have saved grid kWh, and your brake pads from wear.