[RE-wrenches] Fuse sizing in battery circuits

[Troy Harvey]

I've got a question about battery string fusing. Typically we size the wire from the batteries to the inverter based on continuous rating procedures (max power/efficiency)*125%. 

However a 6kW inverter, can peak at 12kW for 5-10 seconds, doubling the source current. That is no big deal for the wire, because it is a short time frame... little heat will be generated. However, in fusing the sub-strings, you need to account for that peak surge current so you don't blow fuses all the time. But if you put a 500-1000 amp fuse on a 4/0 wire, above the max surge draw of the inverter, the wire will be under-protected for its ampacity rating. Any thoughts on the catch-22?


thanks,

Troy Harvey
---------------------
Principal Engineer
Heliocentric
801-453-9434
taharvey at heliocentric.org

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