Did my battery pack balance?

[Stanton]

I had one of those "double charge complete" messages this morning, and now that I can measure the amount of power drawn by my EVSE (via a 220v Modlet), I downloaded the data. Here's what happened in the last day or so:

1) I charged to 100% Monday ending around 5pm (first charge message)
2) About 5am Tuesday, the EVSE drew around 4 Watts for about 2 minutes (second charge message)
Note: I have an 80% daily timer set for 6am.

So the question is: did the pack balance, or was the car checking to see if the timer request (for 80%) was executed? If so, why does it take a couple of minutes (at such a low power level) to verify that? BTW, it drew >17kW total (from the wall) to charge from LBW to 100% (at about 5 temp bars).

 

[davewill]

I'd guess that your timer went off and it was an hour off because if daylight savings issues. That doesn't mean your battery didn't "balance". In fact, I'm pretty sure it balances every time it's allowed to sit for a while at a high enough SOC. I'd expect that only when it's badly out of balance does the process lower the charge level enough to cause the car to charge some more. The "second charge" is a side effect of balancing, not the balancing process itself.

 

[planet4ever]

I'd guess that your timer went off and it was an hour off because if daylight savings issues.

In my experience the timer always signals an hour before the finish time. It makes sense that it shouldn't start charging right at the end time, just in case it might need a boost. An hour seems excessive, but note that the estimated charge times shown on the dash are typically in 1 hour increments, and never of finer granularity than half hour increments.

Ray

 

[Stanton]

Anyone else who knows details about pack balancing? How many Watts does it usually draw?
I know it wasn't a clock (DST) issue; I also know it doesn't balance EVERY time it charges to 100%.
While it does tend to FINISH charging an hour before the target time, it still doesn't make sense that it tried to START charging.

 

[tallgirl]

I just watched mine balance (my entire house electrical system is instrumented -- I watch my fridge defrost sometimes ...) and the charger will turn on and off several times, trying to figure out if its done.

For my batteries, once the bulk of the charge had completed, there were three periods when the charger turned on well below full power -- between 700 and 900 watts each time -- then ran for a few minutes, shut off, and went again. Each "cycle" lasted around 10 minutes.

My guess is that your timer kicked in and the charger checked to see if the battery was fully charged. A few watt-seconds later, it concluded it was and it turned back off. I just heard my end-of-charge message show up on my phone. Not that I can find my phone ...

 

[Stanton]

That's great data! Pretty much confirms that my pack did NOT balance. Now that I have a meter/monitor connected to my 240v feed, I'll know what to check for: something more than a few Watts and longer than a few minutes!

 

[KillaWhat]

Can you force a pack balance?

 

[ebill3]

This balance discussion keeps coming and going. My words to live by are:

http://www.mynissanleaf.com/viewtopic.php?f=31&t=10223&p=236664&hilit=balance#p236664

 

[Nubo]

I believe Nissan's recent sales numbers, judging by the influx of new members. It's all good!

 

[davewill]

That's great data! Pretty much confirms that my pack did NOT balance. Now that I have a meter/monitor connected to my 240v feed, I'll know what to check for: something more than a few Watts and longer than a few minutes!

Remember the pack will balance any time it's charged up and let sit a bit...and you won't necessarily see any "extra" charge cycles going on. The extra charging after a few hours is a reaction to the pack losing enough charge during the balancing cycle to cause the car to start charging again. If the pack is fairly balanced, and if you charge to 100% regularly, you may never see this. Doesn't mean your pack is out of balance...quite the contrary.

 

[Stoaty]

Remember the pack will balance any time it's charged up and let sit a bit...and you won't necessarily see any "extra" charge cycles going on. The extra charging after a few hours is a reaction to the pack losing enough charge during the balancing cycle to cause the car to start charging again. If the pack is fairly balanced, and if you charge to 100% regularly, you may never see this. Doesn't mean your pack is out of balance...quite the contrary.

Does the balancing only happen when the Leaf is plugged into the charging dock and immediate charge is selected (or in the period when timer is on), or does it happen if the car is not plugged in but turned on and not moving? Anyone know?