BMS SOC not resetting

[chrisandbev]

hi,

i have a 200ap Daly bms, i have drained the battery ( 400amp lithium ) on purpose down to check the amp hours with just the fridge set to electric on to see how long the battery would last.
the bms high voltage cut off i have set to 3.65, low voltage disconnect to 2.50.
the battery turned off when the bms showed 0% soc, although the other monitors and shunt both said the battery was at 12.1 v.
i have tried resetting the soc on the bms without any luck,
has anyone got any suggestions as to how the change the soc to its true reading.

 

[Raul]

The voltage can bounce back after removing the load. The voltage threshold is for cell level, not pack voltage. 2,5v lvd does not guarantee 10v pack, some cell can be higher. The bms will cut of on first cell reaching the set value.

 

[Raul]

What are you trying to do or achieve? You don’t reset at low soc, but at 100%. If your bms had dialed in 400ah as total capacity, and then started to count down while you discharged, till bms cut of. That could mean your pack is not true 400ah?

 

[chrisandbev]

What are you trying to do or achieve? You don’t reset at low soc, but at 100%. If your bms had dialed in 400ah as total capacity, and then started to count down while you discharged, till bms cut of. That could mean your pack is not true 400ah?

hi,
all of the 4 cells when the bms turned off were at 3.175 so not sure why the bms turned them off, the soc said 0%. I am or have started to charge them up to full and will try to reset the soc to 100% when full, then i will see if they will last for longer, the cells are wired up in pairs to make a total of 400 amh, i was just wanting to drain them to see what capacity the will deliver.

 

[Raul]

Ok understood. It could be the bms settings are done conservative to save the pack health. For a single test going down to 2,7vpc it’s ok, but for every day cycle you should keep above 3,1vpc, hence the bms settings. It’s not much left below that, maybe less than 5%. Most of the bulk is above that. Same for the 3,65vpc. Your pack should see that voltage only a handfull of times per year for top balancing corrections. Do you have access to the bms settings?

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[chrisandbev]

Ok understood. It could be the bms settings are done conservative to save the pack health. For a single test going down to 2,7vpc it’s ok, but for every day cycle you should keep above 3,1vpc, hence the bms settings. It’s not much left below that, maybe less than 5%. Most of the bulk is above that. Same for the 3,65vpc. Your pack should see that voltage only a handfull of times per year for top balancing corrections. Do you have access to the bms settings?

hi these are the settings