question

ruffmetalworks avatar image
ruffmetalworks asked

battery BMS in safe mode/ recovery

Two questions really. I have 3 new renogy 100ah smart lifpo batteries. They were connected in parallel, activated, then charged using my Victron multiplus for 24 hours. They ran out of power quickly. I isolated the batteries and found one at 84% SOC, one at 22% SOC and one at 0% SOC.

Q: Why would this happen?

Q2: Can the multiplus be configured to pull this battery out of safe mode, it looks like the BMS won't let it charge, it has been on the charger for 24 hours and still at 0%. Oh and the mulitimeter shows 2 volts.

battery charging
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

1 Answer
pwfarnell avatar image
pwfarnell answered ·

Often the battery BMS needs some cycles to learn the SOC in these drop in batteries and may not be correct. The voltage is more important measure of balance, but with lithium small voltage differences can be large SOC differences so connection in parallel needs a really good wiring set up with oversized balanced cables.

Q1. The divergence in SOC could be because of poor parallel wiring that did not have balanced wire lengths or the correct take offs, one of the crimps not made correctly or one of the terminals not bolted and torqued up correctly. It could be because you did not fully charge all the batteries to fully charged before putting them in parallel. It could be because of a deffective BMS in the one battery. Too little information to make an educated guess.

Q2. You will need to follow up with the Renogy instructions as this is a Victron forum. Some need a type of charger that will create a charge voltage of say 14.2V regardless of a battery being connected or not.

1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

pwfarnell avatar image pwfarnell commented ·
From what I have seen with budget drop in batteries in parallel is that the battery SOCs can often diverge 10-20% at times due to small differences in BMS performance and wiring imbalances.
0 Likes 0 ·