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BMS in LG CHEM ESS modules
#11
(12-07-2019, 03:49 AM)w0ss Wrote: no success on the BMS but figured out the connector and pinout. Balance is not the greatest on these if you trust the ISDT BG-8S

Connector is the "MFG : TE Connectivity AMP Connectors / 1318853-2" which cost $5 quantity 1

You only show a 20mV delta in balance... I would say that is pretty good / very acceptable.

I also checked my ISDT BG-8S against my Fluke meter and the values all appear to match up quite well.
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#12
20mv at 3.85V though. Isn't that when the cells have a flatter discharge curve?
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#13
(12-09-2019, 09:18 PM)w0ss Wrote: 20mv at 3.85V though. Isn't that when the cells have a flatter discharge curve?

Refresh my memory… are these Li-Ion or LiFePO4?  It’s LiFePO4 that has a flat discharge curve.
 
Either way, 20mV delta is pretty good, but yes, looking at the delta at 50% SoC isn’t really the best representation of balance.  Have you looked at the balance at the top or bottom ends of SoC?
 
The best thing you can do is test with a RC balance charger.  Fully charge and top balance, then discharge to get capacity and observe the mV delta at the bottom.
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#14
These are li-ion. That is true I am most used to Lifepo4 and li-ion isn't that bad. I will be balance charging them over the next week or two. Still getting everything setup.
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#15
I feel I can pretty reliably figure out SoC based on voltage when it comes to Li-Ion, it’s certainly not a flat curve, especially when compared to LiFePO4.

Still, you are right, your comments regarding balance won’t be answered until you charge/balance, and discharge. Usually balance ugliness does really show itself until you get to the bottom of the SoC, assuming it is top balance.
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