Please check my 48v battery, 3000w inverter system

Been down this rabbit hole myself on the narrowboat, so a few things worth checking before anyone signs off on this as "good to go":

The obvious one — what's your cable sizing between the battery bank and inverter? A 3000W inverter at 48V is pulling around 62.5A continuous, but at startup/surge you could easily see 2-3x that. Undersized cables will cause voltage drop, nuisance tripping, and in a worst case, heat you really don't want near a battery bank.

Fusing — is there a fuse or MEGAFUSE within 300mm of the positive battery terminal? Non-negotiable in my view. ANL or MEGA type, appropriately rated.

What batteries are you actually running? Fogstar Drift cells, a pre-built LiFePO4 pack, lead acid? Makes a big difference to how the system should be configured, particularly if your inverter/charger is a Victron Multiplus — the charge profile needs to match.

BMS comms — if you've got lithium, is the BMS talking to the inverter? Without that link, you're relying entirely on the BMS to hard-disconnect under fault conditions rather than the inverter backing off gracefully. Fine as a fallback, not ideal as the primary protection.

Post your actual schematic or at least a parts list and someone here will give you a proper steer. There's a lot of "looks fine" systems on this forum that aren't fine once you dig into the details.

@AngliaOffGrid raises the right point on cables, but I'd add — don't just look at cross-section, look at length.

A 3000W inverter on 48V is pulling ~62.5A continuous, but factor in surge (2x-3x on motor loads) and you need your voltage drop calculated for that run, not just nominal sizing.

I ran 50mm² on my shepherd's hut build and even at 1.8m I was seeing more drop than expected under surge loads. Ended up going 70mm².

Also — what are your fuse/breaker ratings and their proximity to the battery? ABYC and good practice says fusing within 300mm of the positive terminal.

What inverter is it specifically? A Victron Multiplus behaves very differently under load compared to something like a cheap Renogy unit, and the cable spec recommendations in the manual will differ considerably.

Good points from both above, but nobody's mentioned fusing yet.

At 48V with a 3000W inverter you're looking at ~62.5A continuous, but inverters can pull 2-3x that on startup surge. Your fuse or breaker needs to handle the surge without nuisance tripping, but still protect the cable — not just the inverter.

I'd be sizing the fuse to the cable rating, not the inverter. So if you've run 16mm² (rated ~100A), your fuse should be 100A or under, regardless of what the inverter manufacturer suggests.

Victron's MEGA or ANL fuses are the go-to here — proper DC-rated, not repurposed AC stuff. Seen too many setups where someone's used a random blade fuse inline and wondered why things got warm.

What cable spec are you actually running, and how long is the run from battery terminals to inverter?

@Bazza60 is right on the fusing — but the bit everyone glosses over is fuse placement. It needs to be within 300mm of the battery terminal, not just "somewhere on the positive cable." Seen too many builds where someone's shoved a 100A ANL halfway down a 2 metre run and called it sorted.

Also — what inverter actually is it? "3000W" means nothing without a brand. A cheap unit off Amazon will have a surge rating that's basically fiction, whereas something like a Victron Multiplus will actually deliver. Makes a big difference to how you size everything upstream.

OP hasn't even told us what batteries they're running either. LiFePO4 or lead acid changes the whole conversation.

@SOC_Nerd nailed the placement rule, and @Bazza60 covered the rating — so I'll add the bit that bit me badly on my tiny house build: fuse type matters as much as size.

I originally ran an ANL fuse thinking it was fine, but with lithium batteries the fault current can be absolutely savage — we're talking thousands of amps in milliseconds. Switched to a MEGA or Class T fuse rated for DC interrupting capacity and suddenly everything was properly protected rather than just technically fused.

Victron's own documentation recommends this distinction quite clearly, but it's easy to miss buried in the wiring unlimited guide.

If you're running Fogstar or similar lithium cells, check what interrupting current rating your fuse is actually specified to — the cheapo ANL holders from the usual suspects often don't publish that figure at all, which should tell you something.