Anyone know if a Victron MPPT 100/30 will cope with a 400W panel on a 12V system?

So I'm mid-way through my van build and I've hit a bit of a wall with the solar sizing. Currently running a single 200W panel into a Victron SmartSolar 75/15 but I'm upgrading to a 400W panel (looking at a Renogy 400W monocrystalline) and I'm not sure the 75/15 will cut it anymore.

I've been looking at the Victron MPPT 100/30 as the obvious next step up, but I'm struggling to get my head around whether it'll actually cope with a 400W panel on a 12V system.

From what I understand, the 30A charge current is the limiting factor — at 12V that's theoretically 360W maximum output to the battery. So even if the panel is rated 400W, the controller would just cap it at 30A, right? Does that mean I'd be losing a meaningful chunk of potential charge, or is the real-world difference negligible given UK weather conditions anyway?

My setup:

• 12V system
• 200Ah Fogstar Drift LiFePO4 battery
• Loads are mostly lighting, a compressor fridge, and phone/laptop charging

The panel specs show a Voc of around 48V and Isc of roughly 9.8A, so the 100V input limit on the controller should be fine on that front.

Is the 100/30 the right call here, or would I be better off stepping up to the 100/50 from the off? Don't really want to overspend if the 30A unit does the job in practice.

Anyone running a similar setup who can share real-world figures?

@RayPowell your 75/15 is basically a hamster on a wheel trying to pull a lorry right now, so yes — upgrade time.

The 100/30 will handle a 400W panel on 12V no bother, but do your maths first. That's roughly 33A at peak into a 12V battery, so you

@RayPowell worth double-checking your panel's Voc before committing to the 100/30 — on a cold morning that open-circuit voltage can spike higher than the spec sheet suggests, and the 100V input limit on that controller is the hard ceiling you really don't want to hit.

What's the Voc on the 400W panel you're looking at? Some of the bigger mono panels are pushing 48-50V Voc which gives you comfortable headroom, but others are creeping higher.

Also on a 12V system the 100/30 gives you a theoretical max of around 360W usable charge power anyway — so your 400W panel is just over that. You won't lose much in practice but have you considered jumping to 24V instead? Might be worth it if you're planning further expansion down the line. What's your battery situation currently?

@RayPowell I went through exactly this when setting up my garden office — ended up with a 100/30 on a 12V system and it handles two 200W panels no problem. One thing worth knowing: on 12V the 100/30 is actually limited to around 360W usable input due to the 30A output cap (30A × 12V = 360W), so a single 400W panel puts you slightly over the theoretical max. In practice you'll rarely hit true peak output, but it's worth factoring in. If you think you might add another panel later, jumping to the 100/50 now could save you swapping controllers again down the line — I wish someone had told me that before I boxed everything in on my van conversion project.

@RayPowell just to add to what @DucatoLife is getting at — the 100/30 has a max input voltage of 100V, so you'll want to check your panel's Voc on the datasheet and then apply a temperature correction for cold UK mornings. Typically you multiply Voc by around 1.12 to 1.25 depending on how cold your location gets. Most single 400W panels sit well within that once you've done the maths, but it's worth confirming rather than assuming.

Also bear in mind the 30A output limit. On a 12V battery bank, you're realistically looking at roughly 360W maximum charge power, so a 400W panel will occasionally be clipped slightly at peak. Not a big deal in practice, especially in the UK where we're rarely seeing perfect conditions anyway!

Good shout from @DucatoLife and @Tom1981 on the voltage side — that's the critical bit to nail down first.

On the current side of things, worth noting that a 400W panel on 12V will be pushing significant charge current. The 100/30 is rated at 30A output, so depending on your panel's specs, you should be fine there — 400W ÷ 14.4V (absorption voltage) gives you roughly 27-28A, which sits just within the limit.

One thing nobody's mentioned yet — check your panel's Isc (short circuit current) too. The controller needs to handle that safely, not just the operating current. Most 400W panels sit around 10-12A Isc so you'll almost certainly be fine, but always worth confirming on your specific panel's datasheet before purchasing.