Will it hurt the BMS if the leads to the cells are NOT disconnected first?

[the_uglydog]

I have some Turli 200ah server rack batteries. I need to remove the busbars and BMS connections to top balance some of them. The BMS is in the front compartment and I can't reach the plugs so I have to remove the + and - connections to the BMS first, then the connections to the cells. The mfg. video shows unplugging the leads to the cells before disconnecting the power connections and the cell connections. The battery is shut off and disconnected from all of the others. Will it hurt the BMS if the plugs for the leads to the cells are NOT disconnected first? Suggestions will be greatly appreciated.

 

[Supervstech]

I don’t think so.
It should be fine.
Just be sure there is ZERO load on the battery when you disconnect the leads.
I think the sequence is to be sure and disconnec them

 

[RCinFLA]

Depends if BMS has an activation surge limiter. Some, like JK 16s active balance BMS has a separate MOSFET with series resistors that limits current when BMS powers up. Some unit progressively switch on the parallel MOSFET's so it starts out with higher series resistance.

Some units just trip their overcurrent shutdown when activated against the discharged inverter DC input capacitors.

You can try and pre-charge inverter caps first before connecting BMS battery side input.

 

[the_uglydog]

I have 6 of these in parallel on one inverter. This one I completely disconnected and have let it stand shut off for a day. When they are connected they pre-charge the inverter slowly, no big inrush of power. They all will turn on when the switch and breaker are on and there is power available. I was mostly concerned with disassembly since they showed removing the wire harnesses first, then the connections to the = - terminals. I'm going to balance 3 of them and put them all back online at the same time, just shutting off the system when the operating batteries are at the same voltage, adding these back in and turning it back on.

 

[featherlite]

This post recommends:

Turn off charging/discharging in the BMS settings.

Turn off balancing.

Turn off the on/off switch to the inverter



Pull the plugs for the balance leads out of the BMS.

Disconnect negative [balance lead]

Disconnect positive [balance lead].

Disconnect the rest of the balance leads.

Basic BMS question: When disconnect BMS from LIFEPO4 Cells, does it matter to remove Negtive connect first or Positive one?

Hi Everyone, I am building my very first battery pack from 4x280AH LIFEPO4 cells and Daly BMS so I want to make sure no obvious mistake occur. I will need to remove and reconnect the BMS to the cells several times for top balancing series / parallel and other purposed. My question is when...

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