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Absorption, Float and Equalization settings to trigger BMS balance for Sol-Ark and DIY Lishen 272aH

Keith Moreau

New Member
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Nov 18, 2019
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67
Hello,

I just put together a 16s 48v bank using Lishen 272Ah cells, it's working well. I had to get a 'dumb' JBD 100A 48v BMS while I'm waiting for my 'smart' JBD 100A BMS from Overkill Solar.

I also have a Sol-Ark 12K (wonderful hybrid inverter). The Sol-Ark has several settings for various chemistries, but it's 'lithium' settings seems to rely on CANbus communication so they've advised to just go with the generic voltage settings, some of which apply to Lead Acid. The 'absorption' setting seems to be the 'bulk' charging setting. There is an 'equalization' setting which can be run periodically every number of days and for a certain period of time. There is also a 'float' setting. Here's a screenshot from the manual.

Screen Shot 2021-03-31 at 10.59.27 AM.png

I want the JBD BMS to do some balancing but I think it only balances when the cells are high at 3.6v. I'm not sure if it is just 1 cell or all the cells that need to be high. I've set my Sol-Ark absorption to 58v to at least get some of the cells to 3.6v to trigger the balancing but I've notice that once the voltage reaches that, it's only for a short period of time, and then it drops instantly down to the float voltage which I've set to 54.3v. Thus my BMS never has a chance to start balancing (I think...)

My thought is to set the Equalization parameter to the same or close to the absorption, and set the period to every day and time to a couple of hours. However, I know this will put the cells in a high charge state for too long, which I've heard is bad for the battery.

Any advice on a strategy to get my BMS to balance is greatly appreciated!

-Keith
 
What I would do:

Bulk/absorption = 58.4V max
Float = 54.4V
Equalization - disabled or 58.4V max
Equalization time = 0

BMS set to balance during charge only and to only balance above 3.4V and 30mV cell deviation.

Lower bulk/absorption from 58.4V until you no longer experience BMS cut-off.
Once per week, increase bulk/absorption by 0.1V. If BMS trips, go back down 0.1V and wait another week.

If your cells are healthy, they'll eventually balance. There's no value in rushing it with equalization charges, particularly if you're holding the cells at peak voltage unnecessarily.

I would not pursue your plan unless I had severe cell imbalance, i.e., substantial battery capacity loss > 20%.

If you can charge to 58V and not trip the BMS, your cells are likely sufficiently balanced.
 
My JBD BMS specs say it starts balancing when the cell gets to 3.6 so I can’t adjust this until I get a customizable BMS. I’ll set my absorption to 58.4 and see if it trips the BMS, thanks much for advice.
 
Again, if you can hit 58V (3.625V/cell) without tripping the BMS, you won the battery balance lottery.

If so, I would just give a thumbs up to the universe and direct my attention elsewhere.
 
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