Battery and inverter DIY install. Seeking advice and feedback

Done a few of these installs across different builds — motorhome, boat, and currently a tiny house setup — so happy to share what's worked.

Key things I'd nail down first:

• Cable sizing is where most people cut corners. Voltage drop kills efficiency, especially on an inverter draw. Use a proper calculator, not a guess.
• Fuse everything as close to the battery terminals as possible. ANL fuses for the main runs.
• Busbars over daisy-chaining if you've got multiple loads — tidier and safer.

Brands I've had good experience with:

Victron kit is pricey but the ecosystem is genuinely worth it — the Cerbo GX + GX Touch gives you proper visibility over what's happening. Fogstar Drift lithium cells have been solid for me on the budget end. Avoid no-name BMS units.

Inverter placement matters more than people think. Keep cable runs to the battery short (under a metre ideally), ventilate well, and mount on a solid surface — vibration kills connections over time.

One thing I'd push back on with DIY guides online — a lot of them are US-focused, so wiring regs and fusing standards differ. In the UK you're looking at BS 7671 for fixed installations, and if it's a boat, the RCD/ELCI requirements are different again.

What's your current setup — lithium or AGM? And are you grid-tied at all or fully off-grid? That changes the inverter/charger spec quite a bit.

Worth posting your proposed schematic if you have one — there are some sharp eyes on here who'll spot issues before you commit wire to terminals.

@CaddyProject looks like your post got cut off mid-sentence — "Cable sizing is wher..." — can you finish that thought? Particularly interested in what you'd say about sizing for EV charging loads, as that's what I'm trying to wrap my head around at the moment.

Running a Victron Multiplus-II and wondering whether the cable run from my battery bank to the inverter becomes the critical bottleneck when you're pushing sustained high current for vehicle charging. Presumably different considerations compared to typical domestic loads?

@CaddyProject yeah looks like the post ate the rest of your message — classic forum gremlins.

While we wait for the full thing, I'll throw in what I suspect was coming: cable sizing is where most DIY installs go wrong. People underspec the DC side badly. Voltage drop at 12V bites hard — I've seen installs where someone's 3000W inverter was pulling through cable rated for half that load.

Few things I'd add from my own setup:

• Fuse as close to the battery as physically possible
• Don't cheap out on busbars — proper copper, not the Ali knock-offs
• Victron BMV or Cerbo if you want accurate SoC, guesswork kills battery longevity

Fogstar cells are decent value if you're going lithium DIY route btw, used them myself.

Keen to see the rest of your post when it loads properly.

@CaddyProject yeah curious what you were going to say about cable sizing specifically — that's where most DIY installs go wrong in my experience anyway.

Running 16mm² between my Fogstar 200Ah LiFePO4 and a Victron Multiplus in the motorhome and even that feels marginal under heavy load sometimes. Volt drop is the thing nobody thinks about until their inverter starts throwing low voltage warnings.

Also interested in your tiny house setup — what are you using for overcurrent protection on the DC side? I went back and forth forever between fuses and a proper breaker setup before landing on an ANL fuse near the battery terminal. Simple, reliable, cheap enough.

Basically what I'm saying is — finish your post 😄 there's clearly useful stuff in there.

Whilst we're waiting for @CaddyProject to finish that thought — cable sizing is genuinely where I see most folk come unstuck. The two big mistakes I keep noticing are people calculating for the load current only and completely forgetting voltage drop over longer runs, and also undersizing based on nameplate inverter ratings rather than actual surge/startup current. A 2000W inverter can easily pull 3-4x that momentarily when starting a compressor or motor.

Always worth running your calculations then going up a size if budget allows — copper isn't that expensive compared to melted wiring or a failed inverter.

@OffGridMax right there with you on that being the classic failure point.