Anyone else using a leisure battery as a UPS for their router/NAS during power cuts?

Had a proper frustrating outage last week — about 4 hours, middle of the afternoon, and I work from home so it completely killed my day. I've got a decent solar setup already (2x 200W panels, 200Ah AGM bank, Victron MPPT) but it's all wired up for the shed/workshop, not the house. Got me thinking about putting together a small dedicated backup for the critical stuff indoors — mainly the router, the NAS, and maybe a lamp or two.

I'm looking at something pretty modest. Router pulls about 12W, NAS is around 35W when it's ticking over, so we're talking maybe 50W continuous at most. My thinking was a single 100Ah leisure battery, a small inverter (pure sine, obviously — the NAS won't thank me for anything less), and a basic solar trickle charger to keep it topped up between outages. Total budget around £200-£250 if I'm careful.

The bit I'm unsure about is the changeover side of things. I don't want to be fumbling around plugging things in when the lights go out — ideally it'd switch over automatically or at least within a few seconds. Has anyone wired in a proper automatic transfer switch (ATS) on a small setup like this? Wondering if something like the Victron Phoenix inverter with a built-in transfer switch is worth the extra cost, or if there's a cheaper way to do it without sacrificing reliability.

PikeRuss | 847 posts

@GaryLewis87 Snap — working from home makes you realise pretty sharpish how dependent you are on the router staying alive!

I've been running a 100Ah AGM leisure battery dedicated purely to networking kit for about two years now. Router, NAS, and a small 8-port switch. Total draw is only around 25W, so I get absolutely ages out of it during an outage — honestly more than I'd ever need.

One thing worth doing is grabbing a proper battery monitor (I use a Victron BMV-712) so you're not guessing state of charge. Also make sure your inverter or DC-DC setup is properly fused close to the battery — leisure batteries can dump serious current if something goes wrong.

With your existing solar setup you're already halfway there. What inverter are you currently running?

GlenPalmer93 | 234 posts

@GaryLewis87 Similar setup here and went down this exact rabbit hole last year. One thing worth considering alongside the leisure battery is a proper DC-DC converter rather than running an inverter — your router and most NAS units run on 12V or 19V anyway, so you're wasting energy converting to 240V and back down again. I picked up a decent adjustable buck converter for about a fiver and wired it straight from the battery. Massively more efficient and no inverter noise either.

Also worth grabbing a small battery monitor so you can actually see what load you're drawing — surprised how little a router and NAS actually pull when you measure it properly. Mine's under 25W combined, so even a modest 100Ah battery gives you days of runtime realistically.

SussexWanderer | 1,203 posts

@GaryLewis87 I've been running almost exactly this setup for about two years now — 100Ah AGM leisure battery dedicated purely to keeping my router, NAS, and a small switch alive. Works an absolute treat.

Few things worth knowing: a decent pure sine wave inverter is worth the extra pennies over modified sine, especially for the NAS — some units get a bit unhappy otherwise. Also look at your actual consumption first; my router and NAS together only pull about 25W, so that 100Ah battery lasts considerably longer than you'd expect.

One tip @GlenPalmer93 might back me up on — a proper battery monitor like a Victron BMV is genuinely useful so you're not guessing at state of charge. Saved me from a nasty surprise once.

What inverter are you currently considering? That's often where people underspend and regret it.

Turbo | 2,341 posts

The piece nobody mentions until it bites them: automatic transfer switching. Your router and NAS need to stay alive through the mains failure, not come back up after. A basic relay-based ATS can drop out for 20-30ms during switchover — enough to reboot most routers.

I run a Victron MultiPlus specifically because the transfer time is under 20ms; it's essentially seamless for connected devices. Overkill for some budgets, granted, but worth investigating before you commit to anything simpler.

Also worth checking your NAS documentation — some units have capacitors onboard that handle brief interruptions, others don't. Synology units I've used have been fairly forgiving; QNAP less so in my experience.

@SussexWanderer what ATS solution are you running with your setup? Curious whether you've had any reboot events during switchover.