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SOK 48V 100Ah PRO reports too high battery max. discharging current

WallK

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Apr 3, 2024
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Ukraine
I have SOK 48V 100Ah battery connected to MPPSolar inverter by RS485 (with Pylontech selected as protocol)

It's set up to bypass (to grid) if the battery can't provide enough power, but in my tests BMS turns off by OCP and then the inverter faults with too low bus voltage. Bypass never happens
I've queried inverter for BMS data it has and got in response:

576 -- Battery C.V. charging voltage (I presume in 0.1V)
576 -- Battery floating charging voltage (in 0.1V)
448 -- Battery cut-off voltage (in 0.1V)
0090 -- Battery max. charging current (in 1A)
6450 -- Battery max. discharging current (in 1A)
Some of those settings I can confirm in inverter's menu

So, if 0090 means 90A of max charging current (which is shown as total maximum charging current in inverter menu), that means that inverter thinks maximum discharge current could be 6450A
It's either data gets sent or received incorrectly and the interpreted wrong

I think this is the reason bypass mode never triggered

Could someone check what the battery actually sends?
Maybe @HighTechLab can shed some light on this

Thank you!
 
6450 should probably be interpreted as 65535-64500=103,5A. If the inverter is showing 6450A then it's parsing the response from the BMS incorrectly, or the BMS is sending an unexpected value.
 
6450 should probably be interpreted as 65535-64500=103,5A. If the inverter is showing 6450A then it's parsing the response from the BMS incorrectly, or the BMS is sending an unexpected value.
This number is what inverter interprets BMS data, it's reported by inverter. I did not sniff 485 to check real packets sent by BMS
My assumption is: if charging current is reported by inverter in straight 1A value format -- the discharge is the same
But I could be wrong and your 16bit difference idea looks like a reasonable setting for the battery
 

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