I have 2 160ah victron lithium batteries in parallel. Do both batteries need to be individually fuse or is one single fuse on the string okay? If so what size fuse per battery. For my loads i only need 300 amps.
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Lithium 160ah fuse size
The manual says 1 fuse per string so I'd suggest doing that to avoid warranty issues. I suspect you can use anything between 150A and 300A (with whatever margin stacked on top that you're comfortable with), however use the same fuse rating for both 160AH units.
Note that the fuses are primarily protecting the wiring downstream so shorts can't initiate a fire or other hazardous scenarios. Its not really intended to control the current needed for your loads.
Make sure:
1) your wiring downstream can handle the sum of the two fuse ratings continuously without overheating etc.
2) your fuses have high enough arc interrupting capacity. Even though the spec sheet says max discharge current is 320A, under a worst case short condition it can throw out substantially higher current (don't believe the smart 160AH has an integral cutout relay). If your fuse does not have a high enough AIC the risk is that a short will arc (jump) across the fuse and bypass it when you need it the most.
Personally I'd use a Class-T fuse (like the Busmann ones) which will have more than ample AIC for the units. Whether you want to use a cheaper ANL/CNL fuse depends on your risk tolerance and advice from Victron distributor. Certainly don't go cheaper than ANL/CNL fuses imo.
What batteries do you have exactly?
Did you read the manual? It should be in there...
Basic thinking: every parallel battery a fuse, and / or every series string a fuse. Remember the fuse is mainly to protect the wires attached to it, so for 150A per battery, use a 150A fuse and at least 50mm2 wiring (per battery)
