Connecting a DC waterpump to off-grid system

[Rob James]

Hi, I'm looking for some advice about connecting a 24V DC water pump to an off-grid cottage solar*system.*

My battery and inverter set up is:
- 24V 310 Ah LFP battery bank in 8S configuration
- 150A BMS- Samlex EVO 2224 Inverter/Charger

The inverter has a 12V output, which I plan to use to run the DC fan in an incineration toilet, but I also need to connect a 24V DC water pump.

The simplest way seems to be to connect it directly to the bank, on the inverter side of the BMS.* I could either wire it directly to the terminals on the inverter, or I could connect*to the main positive terminal on the battery, and to the negative wire on the BMS, which will connect directly to the negative terminal on the inverter.* *

This would not give me any fuse protection but it only draws 4.5 amps at peak so not sure that's a problem.

Any issues with wiring directly into the battery this way, so long as I'm not bypassing the BMS?

Thanks!

[Michael Raz]

Don't deal with LFP or a BMS so, with regards to this I can only suggest that it does not really matter which of your options you select for the connection (whichever is easier to wire)
BUT
I will strongly argue with your "This would not give me any fuse protection but it only draws 4.5 amps at peak so not sure that's a problem." statement. How much the pump draws will impact the fuse size but the protection is to prevent a short somewhere in the wires or pump so the pump draw has nothing to do with whether you need a fuse or not - YOU DO!!! Not expensive, easy to wire and will prevent your system (and house) going up in smoke. Depending on the type it can also act as a disconnect for the pump if needed.

[Rob James]

Thanks Michael, solid advice. I've taken a different approach and am going to wire a 120V AC pump into a circuit breaker panel.