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Does this Inverter/BMS setup require a pre-charge circuit?

GVSolar

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I am in the midst of configuring a new lifepo4 battery bank in my off-grid home.
The battery bank will consist of three TechDirect pre-assembled BYD units with an installed BMS - approx 3kwh/105ah per unit. The BMS is rated at 130a continuous but I would derate that to 65 amps per unit based on the attached specs and general caution. The three units will be connected in parallel.
My inverter is the Schneider Conext SW4024 - rated at 3000kw continuous /7000w surge. According to Schneider it has a 16 mF capacitance (as if I knew what that means). So here's my question:
Do I need a pre-charge circuit for my initial inverter inverter hookup - or does the parallel connection of these three BYD/BMS units compensate for the potentially high inrush current?
 

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  • BMS unit - open top.jpg
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  • TechDirect BYD Box Specs.jpg
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  • 8S LFP LifoPo4 BMS.pdf
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There's one thing missing to be able to answer the question: the ESR of the capacitor(s) in the inverter.

However, even if I can't give a number because of that, I can tell you 16 mF is pretty big so the ESR will be low and so the inrush current will be high, probably multiple times higher than what the BMS can handle.

So I highly recommend to have a precharge circuit ;)
 
Its great that we can work around this issue but I hope the product warranty covers this.
 
Do I need a pre-charge circuit for my initial inverter inverter hookup
If you mean by 'pre-charge circuit', a $1 30Ω resister, then, yes, these can be useful to avoid the sparks ... but not essential.
does the parallel connection of these three BYD/BMS units compensate for the potentially high inrush current?
The method of connection of your batteries will have no (negligible) effect on the inrush current.
 
And if you leave your inverter connected you will only need to use the $1 resistor once. Seems worth the trouble and expense!
 
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