18s build with 2x ECityPower bms (6s and 12s) in series

Batteries, Chargers, and Battery Management Systems.
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altermontrealiste   1 W

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18s build with 2x ECityPower bms (6s and 12s) in series

Post by altermontrealiste » Jul 16 2018 7:01pm

Hi ; after putting this bms (https://bmsbattery.com/bmspcm/330-smart ... ent-20_40a) on a 12s battery from a chevy volt pack, I want to make a 18s setup so putting two in series. The bike has a 500w controller.

On the charge side, I have 3x meanwell hrp-300-24v in series (each charging 6s) and I can supply both bms independently (I know the bms cuts at >5A and comes back on, it's ok for me for now).

I'm more worried about the discharge side ; I read on different threads that flyback diodes are required at each discharge fet (viewtopic.php?f=14&t=90476&p=1319696&hi ... r#p1319696), also read that people create an and-gate by powering a relay coil from each bms and when both n/o contacts are made (viewtopic.php?f=14&t=48461&hilit=and+gate+relay), that turns on a contactor with a resistor in parallel for pre-charge.

Would that schematic be safe and functionnal?
series-bms.jpg
schematic v0.1
series-bms.jpg (170.23 KiB) Viewed 111 times
Also, about coil voltages, my 6s would be 24v, my 12s 48v, but for the contactor should I go for 60v or 72v? Are those (https://www.aliexpress.com/item/SAYOON- ... 98156.html) any good?

I dont intend (yet) to push it at more than 10A... is the contactor really necessary in this case or some 40A car relays can do the job?

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