Hi all I'm a newbie and am looking to fit a 2000w inverter in my motorhome. I have 2 x120amphour leisure batteries and need to know what size inline fuse to put in. The inverter is primarily used for charging ebike batteries.

Do you really need a 2000w invertors?

Because 2000w 230v AC device's pulling that sort of power will you around the 180-190 amp range when running from a 12v supply

Hi Slimboyfat46

Your 2000 Watt inverter will draw about 200 amps when fully loaded. If you don't fully load it, it will draw less current. It won't quite be pro-rata, as even with no load it still needs a certain current. If you never intend to use its full capabilities then a lower wattage unit will be a bit more efficient (and smaller/cheaper). The e-bike chargers I have seen have been roughly 100 Watts, so unless you are charging a whole fleet of them at once then 2000 Watts seems like overkill.


To answer your original question, the fuse needs to be rated high enough that it doesn't blow during normal operation, and doesn't drop more than a fraction of a volt when 200 amps is passing through it. This means choosing an automotive fuse, I'd suggest something like a 200 or 250 amp mega fuse.

The fuse needs to be at the battery end, so that the wiring is protected. You haven't mentioned wiring, but with that sort of current you will need a large cross section to avoid excessive voltage drop. Minimising the distance between battery and inverter is vital if you want to avoid the need for really thick, heavy and expensive cables.

I don'tt want to be rude but fitting 2000watt inverters in motorhomes always reminds me of that saying fools rush in where wise men fear to tread
The purpose of the fuse is to protect the wiring between the battery and inverter. Its a complex subject so impossible to give a definitive answer without seeing the wiring. But as a rough idea if you have a 200 amp fuse to use the full capacity of the inverter, you could use short well ventilated 35mm cable. Shorter thicker cable always better.
Better still forget about fitting inverters that size in motorhomes.

The smaller the inverter the better for efficiency and the health of the batteries. A typical E bike charger is specified at 110 to 230v at 2 amp max. Thats around 250 watts as a rough guide for the power requirement. I recommend a true sine wave inverter, the Victron range is reliable,
https://www.12voltplanet.co.uk/victron-phoenix-pure-sine-wave-inverter-12v-375w.html
or slightly more power,
https://www.12voltplanet.co.uk/vict...-wave-inverter-12v-500w-vedirect-enabled.html
Connect to the battery with a fuse as near the battery post as practical, use link (midi) fuses, short cable run 6mm2 cable with 50A fuse, longer run 10mm2 cable with 70A fuse.
Consider that the power taken from the leisure batteries has to be put back and the charging system in the van has to be capable of doing that. A 48v 15Ah battery will take more than 60 Ah out of your leisure batteries, around 25% of the capacity, assuming they are fully charged and actually have the rated capacity, ( which they wont). You will need to keep a close watch on the leisure battery state to ensure that they are over discharged

Mike