HV Relay trip
 

Ok, I've had this Leaf pack in for a few years but in the last few charge cycles my HV relay has kicked off (AKA....Done it's job). Here's a photo of right after the HV relay kicked out.

My settings were recommended by Serigo back in 2020 (Man...I miss that guy!)

Now....it's obviously that first cell that is reaching the 4.08 max volt before the pack voltage is reaching the set limit of 57V. In fact...adding up the above numbers totals 56.895V. But we all know that the pack will "settle" to it's real charge once the charge cycle stops....and it was yapping (beeping) at me for several minutes before I took this pic.

So, "fishing" for opinions. Should I bump up the Max V Per cell? Or "drain" cell #1 to the limits of the other cells? Or I could set my BMS to it's "Dynamic" setting.

This is from the ZEVA instructions:

By default the BMS16 uses a dynamic balance threshold, where any cells more than 1mV (.001) above the average receive balancing. Or, as The threshold may also be set manually – if so it is best to set it to the average maximum charge voltage, so that only cells above average at the end of a charge receive balancing.My settings are as follows:

Max Charge Voltage: 57
BMS Max Volt per cell: 4.10
Balance V per cell: 4.07
BMS Min V per cell: 3.14
Full V: 56V

Thoughts on the matter?

https://i.imgur.com/gYWMn0Q.jpg

Re: HV Relay trip
 

Your pack is a bit more out of balance than I would like to see. I like to see all within 5-10mV at full charge. Other than that, I don't see a problem. I would think that your BMS should do a better job of balancing!

Re: HV Relay trip
 

Yeah….I’m thinking of setting the BMS to Dynamic balancing and that should do the trick.

Re: HV Relay trip
 

My Leaf pack consistently has cell voltages within 5mV when it's up at 4 volts per cell.

Re: HV Relay trip
 

I can't see the picture (picture hosting sites are blocked on my work computer) but you can drain the one cell if you have one that's high. I have an RC Battery pack charger/discharger and while it isn't meant for 100ah packs it does have built in charge and discharge circuits and will pull up to 5 amps continuous. It does eventually complain about 5 amps and stops due to heat but it will actually pull 4 amps for as long as I want it to... Which is good because it'll take it a while...

I can't measure millivolts with my DVM but my cells are all within 0.01v of each other when fully charged. I still manually check my cells about once every 6 months. I check it when the pack is nearly discharged and then again after charging. When almost discharged the biggest difference I saw was 0.02v. That was around 3.35vpc this last time and charged is 4.05vpc.

I probably should get a more accurate DVM and recheck them.

Re: HV Relay trip
 

The one cell that causes the HV relay trip is at 4.084 and the lowest is 4.056

Re: HV Relay trip
 

I changed the ZEVA to do "Dynamic Balancing"....which is pretty much balancing all the time based upon average cell voltages.

So, since the 10 days since my OP, here's the cell numbers at this point.

Still not where I want them to be....but ten days ago the largest variance was 4.084-4.056=.028. Today the spread is 4.062-4.049=.013. So, the "spread" is almost cut in half. Of course, letting the ZEVA BMS do the work takes a lot of time as those shunts aren't that large.

Once they are balanced properly I'll switch back to top balancing....and pay more attention to this in the future!!

https://i.imgur.com/RIaekzA.jpg

Re: HV Relay trip
 

And here's perhaps a more telling analysis of the data. I've enter the cell data on a spreadsheet and determined the average cell voltage for each point of time. Then did the average, then did the cell V vs the Delta (If I'm using the right term) and now three cells are right at the average.


https://i.imgur.com/x45byb9l.png

Re: HV Relay trip
 

Looks like the balancing is doing it's job - but slowly. Your settings are still nice and conservative for max cell voltages.

Re: HV Relay trip
 

Max voltage for a cell is set at 4.1, while the pack voltage is set at 57.0. It’s that #1 cell that hits the max 4.1 before the pack reaches 57V.

Mebby another week before it all works out.