Anyone know if a Victron MPPT 100/30 will work with 24v panels on a 12v battery bank?

Been scratching my head over this one for a few days now and could do with some guidance from people who actually know their stuff.

I've got a pair of 200W panels wired in series giving me roughly 48V Voc sitting on the roof of the van, and I want to feed them into my 12V lithium bank (three Fogstar Drift 100Ah cells in parallel). The Victron MPPT 100/30 keeps coming up in my searches as the obvious choice, but I'm second-guessing myself on the voltage compatibility.

From what I can work out, the "100" in the model name refers to the maximum PV input voltage (100V), so my 48V Voc should sit comfortably within that window. And the "30" is the maximum charge current output — 30A into 12V giving a theoretical max of 360W, which lines up reasonably well with my 400W array. Am I reading that correctly?

What I'm less certain about is the minimum PV voltage relative to battery voltage. Victron's documentation mentions the PV voltage needs to exceed battery voltage by a certain margin before the controller will start working, and I've seen conflicting figures thrown around — somewhere between 5V and 17V above battery voltage depending on which forum you believe.

Has anyone actually run a similar setup — higher voltage panels feeding a 12V bank through this particular unit? Keen to know:

• Whether it starts up reliably in low-light conditions
• If there are any gotchas with the Bluetooth app configuration
• Whether the 30A output is genuinely achievable or whether I should be looking at the 100/50 instead

Any real-world experience would be massively appreciated.

Hey @WelshCamper, yes that'll work absolutely fine! The 100/30 is rated for up to 100V input, so your series pair sitting around 48V open circuit is well within spec. The MPPT controller handles the voltage step-down to charge your 12V bank - that's literally what it's designed for.

One thing worth double-checking though: your panels' open circuit voltage (Voc) will be higher than the nominal 48V, especially on cold mornings when panels run cooler. Dig out the spec sheet and check the Voc figure, then factor in your coldest likely temperatures. You want to make sure you're staying comfortably below that 100V ceiling.

Also worth noting - with 400W of panels into a 30A controller on 12V, you're pushing the limits a bit (30A × 12V = 360W), so you may occasionally clip some power on bright days.

@WelshCamper worth double-checking your Voc in cold conditions — panels can spike notably above their rated open-circuit voltage when temperatures drop, and in Wales that's not a trivial consideration. Take your panel's Voc spec and multiply by around 1.13 to get a worst-case cold weather figure. If that stays under 100V you're golden.

I ran a similar config on my garden office — 2x panels in series into a 12V bank via the 100/30 and it's been faultless for 18 months. The MPPT does all the heavy lifting converting that higher voltage down efficiently.

One thing @BoxerConvert may have already covered — make sure your battery charge profile is set correctly in VictronConnect. Easy to miss if you're new to Victron kit.

Good points from @BoxerConvert and @NeilJackson already. One thing worth adding: make sure you configure the 100/30 correctly in VictronConnect for a 12V battery bank — it can auto-detect, but I'd set it manually to avoid any ambiguity on first connect.

Also worth noting: at 12V with a 30A output ceiling, your actual usable power is capped at around 360W. With 400W of panels in series you're slightly over that, so you'll occasionally be curtailed at peak irradiance. Not a disaster — the controller simply clips the output — but factor that into your sizing expectations.

For a static setup I'd personally have gone 24V battery to make better use of those panels, but if 12V is already committed, the 100/30 will handle what you've described without issue.

Ran into exactly this setup on my boat last summer — 48V-ish input into a 100/30 feeding a 12V bank. Works a treat.

The one thing nobody's mentioned yet: keep an eye on your charge current at high input voltages. The 100/30 will throttle its output to protect itself from overheating, so on a blazing August afternoon you might not see the full 30A you're expecting. Doesn't mean anything's wrong — it's just the controller being sensible.

Also worth grabbing the VictronConnect app and logging a few days of data early on. You'll spot anything odd pretty quickly, and it's oddly satisfying watching the yield graphs when the sun finally decides to show up in Wales. 🌤️

@WelshCamper to add to what's already been said — the 100/30 is rated 100V input max, so your ~48V series string is well within spec. On 12V battery, you'll get up to 30A output, so your theoretical max from 400W is ~33A... you're right on the edge but panels rarely hit true peak simultaneously so you'll be fine in practice.

One thing nobody's mentioned: check your minimum battery voltage setting in VictronConnect. New installs sometimes have it slightly off and the MPPT can behave oddly on a partially discharged 12V bank.

Also worth enabling the panel voltage history after a few days — useful for spotting if you're ever clipping, though I'd be surprised given your array size.

Solid choice of controller for a garden office or similar — I use one myself feeding a 12V setup without any grief.