Overkill Solar Review

Dynoman

Solar Enthusiast
Joined
Dec 17, 2020
Messages
129
Location
Michigan
No, per code the BMS cannot be your Overcurrent Protection for the inverter. Yes, the BMS will limit the current and can even open the circuit, but that is not the OCP that NEC is referring to. A BMS will not qualify as the OCP for the inverter. In some cases the BMS could fail too due to a high surge or short ckt of the battery bank. So no, you MUST have a fuse/CB between the battery bank and the inverter, per code, and for your own safety.
We are discussing a wire-fire in another thread, where the user didn't have a fuse and was relying on the breakers in the multiple battery packs to protect the main line. It didn't. The inverter failed and the BMS (or something) limited the current to a value that just kept re-igniting the wire insulation, but nothing tripped. Had there been a fuse/CB between the battery and the inverter, it would've protected those wires and prevented a fire. Luckily no one was injured.

Good point fuses or circuit breakers are always needed for circuit protection in any electrical circuit and they do trip or blow to limit current in a short circuit or over current condition. For Lifepo4 batteries a high arc flash (T-Fuse) is recommended in the positive cable run from the battery to the inverter. The OP was asking if the BMS would limiting current and the BMS will do that, but is not typically referred to as circuit protection. It is used for cell protection of the battery. Maybe I misunderstood his question.
 

Moltensurf

Solar Enthusiast
Joined
Oct 18, 2020
Messages
135
Good point fuses or circuit breakers are always needed for circuit protection in any electrical circuit and they do trip or blow to limit current in a short circuit or over current condition. For Lifepo4 batteries a high arc flash (T-Fuse) is recommended in the positive cable run from the battery to the inverter. The OP was asking if the BMS would limiting current and the BMS will do that, but is not typically referred to as circuit protection. It is used for cell protection of the battery. Maybe I misunderstood his question.
I believe it’s calling for a circuit breaker in line. I have one ordered up
 
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