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I was of the understanding that the battery should be charged to 100% on occasion such that the cells can be rebalanced. Does anyone know if the limitation to 90% charge still allows this balancing to take place?
 

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I was of the understanding that the battery should be charged to 100% on occasion such that the cells can be rebalanced. Does anyone know if the limitation to 90% charge still allows this balancing to take place?
It seems to balance at the end of the charge. The cell voltages that go over 4.100 while the battery is still having energy put into it drop back down to 4.100, this happens repeatedly.
 

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There's either active or passive balancing that occurs when my 2019 is unplugged and parked. I imagine this is passive balancing. I've been watching my high and low cells everytime I drive the Bolt, for the last two or so months now.
 

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There's either active or passive balancing that occurs when my 2019 is unplugged and parked. I imagine this is passive balancing. I've been watching my high and low cells everytime I drive the Bolt, for the last two or so months now.
So are you saying the voltages tend to level out after unplugging from a charge? I have never seen this happen on our 2017. The same cells are always high, and low. The amount of spread is about 0.020-0.025 volts at high SOC, and low SOC. It is least at the middle of the charge. As low as 0.010-0.012 volts. This makes sense because voltage rises most dramatically at the top, and falls off most dramatical at bottom. In the center, the voltage slope is close to flat, so even the same spread in SOC would show smaller voltage spread.
 

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So are you saying the voltages tend to level out after unplugging from a charge?
Indeed. I haven't watched it in action (I imagine it's a bit like watching grass grow), but I've observed this on several occasions. I'll have to post some screenshots tomorrow.
 
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There's either active or passive balancing that occurs when my 2019 is unplugged and parked. I imagine this is passive balancing. I've been watching my high and low cells everytime I drive the Bolt, for the last two or so months now.
That could be just the cells reaching some equilibrium on their own. Like all rechargeable batteries, there is some self discharge over time and the higher the SOC, the faster the self discharge. So the higher cells may just be discharging faster than the lower cells and closing the gap a bit. I've not observed any noticeable balancing with my 2019 when unplugged. I tend to get the same .2V variance no matter when I take the measurements, but I only charge to 80%.

Mike
 

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Thank you very much.

I have been monitoring our cells, using Torque Pro, since June of 2018. I have never seen cell voltages dropping after charging to hilltop 87-90% SOC. I have never seen any self-discharge from our pack. At full 100% SOC I never leave it at that level for more than an hour, but have never seen anything like a drop of 0.065 volts, from 4.165 volts average to 4.100 in that time.

What folks may be seeing is what is called "surface charge" Since the voltage goes up very steeply at the end of charge, there is really very little energy stored at that voltage. The loss of a few Wh from a 60 kWh pack, due to computer and sensor drain, may not show up as voltage loss at a slightly lower SOC.

Here is our Bolt, charged to ~50%, and left unplugged in our garage for two weeks. The total average cell voltage drop was 0.001 volt. This could easily be explained by battery conditioning during the two weeks..

Seattle leave.jpg Seattle back.jpg

It is interesting, although perhaps only random, that the highest cell in the pack dropped, while the lowest did not.
 
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