Anyone else using a small inverter/charger as a UPS for home networking kit?

After the third power cut this winter I finally got fed up and cobbled together a proper backup setup for my router, switch, and a couple of POE cameras. Running a Victron Phoenix 12/500 with a 100Ah AGM on a drip charge from a Victron Blue Smart 12/15 charger. Total draw on the network kit is around 45W, so I'm getting well over 12 hours of runtime without breaking sweat.

The bit I'm still not happy with is the switchover time. The Phoenix isn't a true UPS — there's a noticeable half-second or so gap when mains drops before the inverter kicks in. The router survives it fine but my Unifi Dream Machine reboots every single time, which is annoying. I've read about putting a small capacitor across the DC output but I'm not sure that's actually practical at this scale.

Has anyone found a clean solution for that switchover lag without jumping all the way up to a proper online double-conversion UPS? Ideally I want to keep it 12V DC based so it ties into my existing solar setup eventually. Wondering if something like the Victron MultiPlus even in its smallest form would be overkill for 45W of load.

RhysLee78 | 47 posts

@BKU_Electric snap! Done almost the exact same thing here after a nightmare outage last February knocked out my CCTV right when I needed it most. I went slightly different route though — using a Multiplus 12/500 rather than the Phoenix so I get the automatic transfer switching built in. Seamless changeover, networking kit doesn't even notice the grid has gone down.

One thing worth checking — what's your idle draw looking like? My router, switch and NVR together pull about 35W continuous, so the 100Ah battery gives me a solid two days of runtime which is plenty for most outages up here in Wales.

Have you set a proper absorption/float profile for your battery chemistry? Makes a big difference to longevity long-term.

Turbo12 | 203 posts

Great minds @BKU_Electric! I went down a similar route about 18 months ago but opted for a Victron MultiPlus Compact 12/800 instead — slightly overkill for just networking gear but means I can throw a NAS and a couple of desk lamps on there too without sweating the wattage.

One thing worth mentioning that caught me out initially: make sure your transfer time is actually fast enough for your router to stay up. Some cheaper units have a noticeable switchover delay and the router just reboots anyway, defeating the whole point! The Victron kit handles this brilliantly with its near-zero transfer time.

Also worth keeping an eye on your battery temperature over winter — I've got mine in an unheated garage and capacity drops noticeably when it gets properly cold. A temperature sensor on the charger makes a real difference.