Battery "balancing" at an 80% charge

[Stanton]

Wow: lots of questions. I'll answer a few of the obvious ones:
1) yes, I did a "timer over-ride" charge (to an 80% timer)
2) no other over-lapping timers
3) I use a modified Nissan L2 EVSE (always have)
4) I've left it plugged-in before (and even longer--like 12 hours), but I only remember getting a couple of these "double complete" messages in the last 6 months or so. Note: I purposely avoid letting it sit @100% during the summer here (I've been seeing 5TB's lately)
5) no lost capacity bars yet (see sig)

I don't have any way to measure exact energy consumed from the wall (or a GID meter--waiting for a LeafScan), but I really think there's a correlation between: cooler weather, a couple of cell balancing events, and (occasionally) getting my 10 bars @80% charge back (instead of 9 bars). In fact, I'm really curious to see what happens with my next few 80% charges

 

[planet4ever]

Last Thursday night I plugged the car in for a charge to 80% as usual. I have an end-only timer set for 7AM, but it finished much earlier than that, at 4:54AM according to the "Charging Stopped" message. This was a bit out of the normal, but no great surprise to me, as my timer has always been way too conservative. My 7AM target is usually met some time between 5:30 and 6:15.

So, why am I posting here? Because I didn't use the car at all on Friday, and didn't even unplug it. And I got a second "Charging Stopped" message Saturday morning, more than 25 hours after the first one. I can't believe this was a balancing message. The real tip-off is that the message was sent at 6:01AM. Clearly something decided that the battery was below 80%, and the timer decided to give it a one-hour boost. It only took one minute to bring it back up to 80%.

The SOC could have dropped a bit just due to sitting for a day, or the capacity could have increased due to a temperature change. Since this isn't the first time I've left it plugged in for an extra day, and I've never seen this before, I suspect temperature. The car sits outside, and our autumn nights are getting a bit cooler. The newspaper isn't very accurate, but it did report 51°F here that night. (I know, still balmy!)

This doesn't prove anything, but does add a bit of credence to the suggestion that the second message is triggered by temperature change rather than balancing. Or it could be that some random fluctuation caused early termination of the charging Friday morning, and the car made up for it Saturday morning.

Incidentally, charging also stopped at 4:54 this morning! But we used the car today, so won't be able to repeat the test tonight.

I have 12 capacity bars, have never seen only 9 bars after charging to 80%, and have been seeing 5 temperature bars most evenings when plugging in, but occasionally 6. I've put 10,500 miles on the car in 18 months.

Ray

 

[ebill3]

I have my timer set to 80% - start at 1210 PM and end at 1210 PM. Frequently it will sit plugged in for a day or two, and I get a charge complete email every day at 1210. If I happen to be in the garage, the three lights are on steady.

First time it happened, I thought: "Wow, balancing!" A forum member suggested it might be the timer kicking in. Now I'm sure it just starts to charge, BMS says "charged", and it shuts down.

EDIT 10/30. After use yesterday, the car charged until about 7 PM. Did not use or unplug the car today, and right on schedule at 1210 received the 'charge complete, 10 of 12 bars' message.

 

[ebill3]

New happening for me today.

Car was plugged in for an 80% charge after very brief use from an 80% charge.
Charge stopped message three times this afternoon - 3:23, 3:24, and 3:26.
The period was not over a start/stop timer setting.

No power outages, blips, or anything out of the ordinary.

 

[DNAinaGoodWay]

I can assure everyone that the Leaf pack does balance throughout the charge, even when under 80%. A restart after 80% is rare though. The most accurate balance is going to come from a full charge.

Let me remind everyone, you do not need to worry about it, or have a special charge regimen. I advise a full charge at least once in a while, say once a month minimum, but if you don't need the range, only charge to 80%.

You'll get maximum charge (range) when you need it if you occasionally perform the top balance. Other than that, it doesn't have much impact on battery life/health, as the automatic systems keep it in-line.

-Phil

Thanks Phil, this is the info I was searching for.

Just one question, how long should it be left once it hits 100% for optimum balancing ?

 

[Ingineer]

Thanks Phil, this is the info I was searching for.

Just one question, how long should it be left once it hits 100% for optimum balancing ?

An hour is likely more than adequate. I always charge to 80%, and when I think I might need the range, I top off to 100% a few hours before my trip, leaving about 30-60 minutes if possible before leaving. That allows the top balance, and also the battery cools down a bit.

Avoid letting it sit for long periods after a 100% charge. Just try to schedule it like I do, before a trip.

-Phil