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Re: How often to "Cell Balance"? Weekly? Monthly? Depends?

Posted: Tue Jul 02, 2019 11:42 pm
by LeftieBiker
I thought it would bleed charge from the high cells with the shunt resistors.
I don't see why it would need to be plugged in to do that.

Re: How often to "Cell Balance"? Weekly? Monthly? Depends?

Posted: Wed Jul 03, 2019 5:35 am
by DaveinOlyWA
Reagle wrote:My car had a bad battery cell (actually a pack of 2 I think) replaced at 8k miles a few months ago, and it still can't seem to get its balance back. the new cells are a good 80mV above the rest.. Any suggestions? I've been contemplating deep discharge but it's a hassle. I suppose I can try leaving it plugged in after charging for a while if most balancing happens at the tail end. Currently it's charged on the timer and usually is ready 30 minutes or so before I leave, so it never actually sits for a long time plugged in

Question; How much of a reduction are you seeing in "full" charge range?

Do you need that full charge range?


If you answer is "not much" or "don't know" on the first and "No" on the 2nd, then don't worry about it. Eventually the pack will self balance. Balancing current is very low but will be on "all" the time.

The only real drawback is range at full will be hampered as the high cells will trigger BMS to shutdown early. There are a few things you can try but none would be good for the overall health of the pack so I would let it go.

Re: How often to "Cell Balance"? Weekly? Monthly? Depends?

Posted: Wed Jul 03, 2019 8:12 am
by Reagle
So far GOM range is unchanged after full charge, but Leafspy is reading lower SOC than the car reports. It used to be the other way around..
I can see this being a problem if these cells hit OV limit during charge before normal taper ends and that terminates charge early. But I suppose that should extend the life of the pack ;)
Scary part is even the Leaf tech at the dealership has no idea what cell imbalance means :(

Re: How often to "Cell Balance"? Weekly? Monthly? Depends?

Posted: Thu Jul 04, 2019 7:52 am
by DaveinOlyWA
Reagle wrote:So far GOM range is unchanged after full charge, but Leafspy is reading lower SOC than the car reports. It used to be the other way around..
I can see this being a problem if these cells hit OV limit during charge before normal taper ends and that terminates charge early. But I suppose that should extend the life of the pack ;)
Scary part is even the Leaf tech at the dealership has no idea what cell imbalance means :(
If you want LEAF Spy and the GOM to match, check it about 80% SOC ;)

Not to steal a weather analogy but if you don't like what you see in LEAF Spy, just wait a minute.

In both cases, neither the weather or LEAF Spy is to blame. LEAF Spy reports the true state of the pack so when fully charged, the GOM will say 100% which is the "usable" charge while LEAF Spy may say 97% which is the actual charge. Now if that is all there is, then no problem.

BUT....

Nissan, like ALL car manufacturers sees fit to build in a reserve and also feels we are not mature enough to know about that reserve so its hidden.

This means the LEAF Spy SOC starts out a few points below the GOM SOC but by the time the GOM starts blinking, LEAF Spy will be 10 points up.

Starting on the 40 kwh, Nissan added another low pack "alert" where the SOC meter goes from 2% to "_ _ _" which happens around 38-40 GIDs.

https://daveinolywa.blogspot.com/2019/0 ... at-my.html

Re: How often to "Cell Balance"? Weekly? Monthly? Depends?

Posted: Sun Jul 07, 2019 12:21 pm
by Tsiah
specialgreen wrote:
I don't know if the shunted energy is a trivial amount, or if shunting happens outside of charging (maybe it happens all the time).
The pack shunts cells any time there is an imbalance in the pack, not just during charging.