Does anyone know if a Victron SmartSolar 100/30 can handle two separate battery banks without a combiner?

I've got a fairly standard setup in my Transit — 200W of panels on the roof feeding into a Victron SmartSolar MPPT 100/30, with a single 100Ah lithium leisure battery. Works a treat. But I'm now thinking about adding a second 100Ah battery in a separate locker for a dedicated 12V compressor fridge circuit, and I want to keep the two banks isolated from each other rather than just paralleling them together.

From what I can gather, the MPPT only has one battery output, so you'd normally need some kind of DC-DC charger or a VSR/combiner relay to get charge into a second bank. But I've seen a few people online mention wiring straight off the MPPT load output instead — which on mine is rated at 30A continuous. I'm not sure if that's actually a viable charging path for a lithium or just asking for trouble.

Has anyone done something similar, or got a clean solution for keeping two banks separate but both charged from one MPPT? I'd rather not add a whole second solar controller if I can avoid it. Budget is tight and roof space is already pretty much maxed out with the two panels I've got.

Reply by VivaroSolar:

@WildMechanic the short answer is no — the 100/30 only has a single battery output, so it can't independently manage two separate banks. It'll just see whatever's connected to those terminals as one combined system.

If you're wanting to keep the banks genuinely separate (say, a starter battery and a leisure bank), you'd need either a battery-to-battery charger like a Victron Orion-Tr Smart running off the existing setup, or a second MPPT dedicated to the second bank.

What's the plan for the second bank — extra capacity or keeping it isolated for a specific purpose? That'll change which route makes most sense for your Transit build.

Reply by WhatsAFuse:

@WildMechanic to expand on what @VivaroSolar is getting at — your practical options are either a battery-to-battery charger (B2B) between the two banks, or a Victron Orion-Tr Smart if you want proper DC-DC isolation and charge profiles. The Orion handles lithium-to-lithium really well and integrates nicely into the VictronConnect ecosystem you're already using.

The other route is a simple busbar/combiner feeding both batteries from the MPPT output, but that only really works cleanly if both banks are identical chemistry, capacity, and state of charge. Mixing banks directly without isolation is asking for grief long-term.

What's the second bank for — extra capacity or a separate 12V circuit? That'll change which approach makes most sense.

What @WhatsAFuse and @VivaroSolar have covered is correct, but worth adding: if you go the combiner route, make sure any battery-to-battery charger you use (Victron Orion-Tr Smart is the obvious choice) is properly configured for your lithium chemistry on both banks. I made the mistake early on with my garden office setup of assuming a generic profile would do — it won't if the banks have differing capacities or state of charge. The MPPT charges bank one, the B2B handles isolation and correct charge profiling to bank two. Keeps everything clean and the 100/30 never needs to know there are two banks at all.

Reply by FETGeek:

@WildMechanic To expand on what @VivaroSolar is getting at — the 100/30 has one battery terminal pair, full stop. You cannot natively charge two isolated banks simultaneously without external help.

What you actually want is a DC-DC charger (Victron Orion-Tr Smart is the obvious choice) between your primary bank and the secondary one. Your MPPT charges bank one, the Orion handles bank two with proper charge profile control — both banks stay isolated, no balancing headaches.

Alternatively, a battery-to-battery charger like the Sterling Pro Batt Ultra works well if you're not already in the Victron ecosystem.

I ran a similar dual-bank arrangement in my garden office shed build — separate lithium and lead-acid banks on the same MPPT is genuinely asking for trouble without isolation, the charge curves are completely incompatible.

What chemistry is the second bank going to be?

Reply by VoltChloe:

Worth adding from a practical standpoint — I ran a similar question past Victron's own documentation when setting up my shepherd's hut battery bank, and the short answer is: one MPPT, one battery bank. The controller doesn't know about or manage multiple banks independently.

If you want true isolation between two banks (say, a starter battery and a leisure bank), a Battery-to-Battery charger like the Victron Orion-Tr Smart is often cleaner than a combiner in the long run. Gives you proper charge profiles for each bank rather than just passively splitting current.

@FETGeek's point about the single battery terminal is the key constraint here — work within that limitation rather than against it.

Good timing on this thread — I went through almost exactly this headache when I was setting up my garden office build last year.

The short answer is no, the 100/30 won't natively manage two separate banks. It sees one battery output, full stop.

What I ended up doing was running both banks in parallel through a Victron Cyrix-Li-Charge relay, which intelligently connects the secondary bank once the primary hits a certain voltage threshold. Keeps them logically separate for monitoring purposes but the MPPT only ever "sees" one bank.

@FETGeek is right about the terminal limitations — don't try to bodge two banks directly onto that output terminal. Learned that lesson the hard way with some scorched wire insulation before I knew better.

The Cyrix solution cost me around £60 from a UK marine supplier and it's been rock solid since.

From my narrowboat experience, I ended up with exactly this dilemma — domestic bank and a starter battery both wanting charge attention. What actually solved it cleanly was adding a Victron Battery Protect and a Cyrix-Li-Ct combiner relay, letting the MPPT focus on the domestic bank whilst the combiner handles starter top-up once voltage hits a threshold.

It's not glamorous, but it's rock solid. Fogstar lithiums on the domestic side have been brilliant with this arrangement over two winters.

@WattHelen's garden office build probably threw up similar compromises — there's rarely a tidy single-device solution when you're managing two chemistries or priorities simultaneously.

The SmartSolar only has a single battery output terminal, so no, it can't natively charge two isolated banks simultaneously. What you can do is connect the MPPT to your primary lithium bank and then use a DC-DC charger (Victron Orion-Tr Smart is the obvious choice) to handle the secondary bank properly. That way each bank gets correctly profiled charging rather than a compromised compromise voltage.

I use exactly this arrangement on my boat — MPPT to the house bank, Orion handling the starter. Works reliably and you get full BMS protection on both sides.