Does 12 V water pump need a fuse

[RanVan]

I am hooking up a 12 V DC fresh water pump to my 24 volt LiFePO4 system (8 x 280 Ah Eve batteries) via a 24/12 V transformer. The pump can take at most 9.5 A. Should I put a 10 amp fuse between and batteries and the transformer or can I just go directly to the transformer?

 

[Supervstech]

Fuse… ALWAYS fuse loads.

 

[MisterSandals]

Should I put a 10 amp fuse between and batteries and the transformer

Yes. You might want 15a if you start blowing fuses needlessly.

 

[kenryan]

You say that the pump "can take at most 9.5 amps" but I think what you really mean is that the pump will draw a maximum 9.5 amps.

Size the wire from the pump to the power source for at least 9.5 amps. If the wire is long, you need to consider voltage drop, which might prompt you to use a larger wire size. Once the wire size is selected, insert a fuse close to the power source that is rated for less amperage than the wire.

The fuse is there to protect the wire, not to protect the pump.

 

[RanVan]

Thanks to all

 

[rmaddy]

Is your 24->12V DC converter just for the water pump? If so, it would be far more efficient to get a 24V pump and avoid the converter. If the converter is also used for other 12V items then it's fine.

 

[Pappion]

Definitely put a fuse on the transformer input power connection. I don't trust electronics, they tend to hard short failure. A 10A fuse is fine for this 24v connection, running at 5A-6A. You don't want your wires turning into a glowing cigarette lighter.
On the 12v side you may want to protect your transformer from a defective or stalled pump. To prevent nuisance blows fuse should be at least 30% higher than load current. So 15A would be OK, depending on transformer output.

 

[time2roll]

If the wire is less than 10" and well protected you might skip the fuse. Otherwise #12 wire and 15 amp fuse close to the power source is what I would use. Maybe larger wire if the run is long.