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Old 11-09-2018, 06:31 PM   #1
DaveTM
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Default BMS High Voltage shutdown...Why?

My ZEVA BMS now shows a red header that states : BMS Status Stopped I was going to just post my data, but I thought it may be better to post pic's of the individual screens. The last pic was after I reset the BMS to clear the warning. I'm somewhat perplexed as I have my per-cell set to be 4.08....yet I'm only getting charging to each cell of 4.006-4.009. And when I take my upper charge of 57.0V and divide by 14, I get 4.071-V per cell.

So...why can't I get the pack charge up to 57.0-V?



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Old 11-09-2018, 10:01 PM   #2
NCPW
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Default Re: BMS High Voltage shutdown...Why?

Dave, you'll need to set you max bms setting to something higher than 4.08v if you're balancing at 4.07v.

I'd bump my max to 4.12v and you'll still be way under max voltage per cell the Leaf cells call for and have enough room for all your cell to balance around 4.07v.

On a side note, I think you're leaving a lot of amp hrs on the table by charging so low. I understand wanting to get the most life out of your pack but I think you're shorting yourself a lot of run time.

I have mine set to balance at 4.14v and max at 4.19v. Mine charges to 58.4v but after sitting a few hours ends up settling at 57.6v (4.11v/c).
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Old 11-09-2018, 10:10 PM   #3
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Default Re: BMS High Voltage shutdown...Why?

Thanks NCPW. I thought that's the scenario that I was looking at....but before I bumped up the charge....and the "spread" I just wanted someone else to confirm this.

Your input is greatly appreciated. Thanks very much!!

Dave
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Old 11-09-2018, 11:07 PM   #4
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Default Re: BMS High Voltage shutdown...Why?

The issue here is the most important setting that You left off, the "Balance voltage".

That value determines when the shunts start to by-pass cell current and regulate the cell voltage so that value cannot be lower than the average cell voltage at full charge or they will all be ON and generate a lot of undesirable heat.

Balance Voltage = (Charger Voltage) 57v / 14 cells = 4.08v

The "Max Voltage" needs to be set higher than the average cell voltage at max charge in order to allow the slower cells to reach full voltage, the higher cells will be shunt down after the charge is finished to the "Balance Voltage" setting.

I Would set Max Voltage = 4.15v
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Old 11-10-2018, 08:09 AM   #5
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Default Re: BMS High Voltage shutdown...Why?

Thanks Sergio. (And of course NCPW)

Sergio....not to be a PITA here, but 57v/14=4.071. I dunno if setting the Balance Voltage to 4.07 or 4.08 is a significant difference.

Just "doin the math" here shows NCPW "spread" to be 4.19-4.14=.05 and your suggestion of 4.15-4.08=.07.

BTW, (upon re-reading the instructions for the n-th time) it states for Full Voltage:Typically set value to just below your peak charge voltage. So, since my Max Charge Voltage is set at 57v, I should set the Full Voltage to 56V.

So, for these select settings, I will change\set them to be:

Pack V =57
Full V = 56
Max V = 4.15
Bal V = 4.08

Dave
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Old 11-10-2018, 08:31 AM   #6
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Default Re: BMS High Voltage shutdown...Why?

The balance voltage "cannot be lower" than average, so you always round up in this case 4.0714V => 4.08V

Ag4ever reported issues with the SOC resetting after a full charge even though he had his "Full Voltage" setting already higher than the "charge voltage". This could be a result of his SOC that is tracked by a CAN sensor interacting with a power down CAN bus during "sleep" mode, but he has not asked Zeva (I think) yet.

The only reason to make a bigger spread between "avg cell voltage" and "max cell voltage" in your case (no Regenerative current) is to allow a slight unbalanced pack to "Top Balance" after a full charge cycle.

The cells should all be near the "Balance Voltage" after the "balancing cycle" that follows the "charging cycle" finishes.
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Old 11-10-2018, 09:05 AM   #7
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Default Re: BMS High Voltage shutdown...Why?

Got it. Made the changes and plugged in for a charging test. My voltage should come close to 57V upon a full charge. I'll see how these settings work out.

Thanks again!

Dave
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Old 11-10-2018, 11:17 AM   #8
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Default Re: BMS High Voltage shutdown...Why?

My charger is just about finished using the new settings I put in. Right now the BMS shows the charger is just "topping off" the charge at ....I think it was 4amps or maybe even .4amps.

In any event, the pack charge is right now at 57.4, and a peek at the individual cell volts are at most 4.09 with some at 4.08X. I'll get another reading when I return home later this evening.

On the plus side, this settings input has been a learning curve for me. And another plus is with the current settings, my HV relay has not tripped!!
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Old 11-10-2018, 07:36 PM   #9
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Default Re: BMS High Voltage shutdown...Why?

After sitting for about 7 hours, the pack charge now sits at 56.8V.

FWIW
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Old 11-11-2018, 10:51 AM   #10
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Default Re: BMS High Voltage shutdown...Why?

That is already pretty close to your target voltage, but if all of the cells ended up pretty close in voltage, You can turn the "Balance Voltage" to 4.09V to see if the shunts finish their cycle at a slightly higher voltage.
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