Anyone else using a Victron Cerbo GX with mixed battery chemistry — worth the hassle?

So I've ended up in a bit of a situation with my system. Started with two 100Ah AGM batteries I salvaged a couple of years back, then added a pair of Fogstar Drift 100Ah LiFePO4s last spring when the price dropped. They're on separate strings with their own MPPTs — a Victron SmartSolar 100/30 on each — but I'm trying to pull it all together under one Cerbo GX for monitoring.

The Cerbo handles it fine technically, just shows both banks in VRM which is genuinely useful. The headache is the charge profiles are completely different, and I keep second-guessing whether the AGMs are getting a proper absorption cycle when the Fogstars are sitting there essentially full and throttling back the solar input. It's not a clean setup by any stretch.

What I'm really wondering is whether anyone's gone down the route of using two completely separate MPPT profiles and just accepting the banks will never play nicely together, versus trying to bridge them somehow. I've seen a few threads suggesting a DC-DC charger between banks but that feels like adding complexity for the sake of it.

Has anyone actually run this kind of mixed setup long-term on a Cerbo, or did you eventually just bite the bullet and standardise on one chemistry?

@HarbourKev mixed chemistry is a proper headache tbh. Running AGM and LiFePO4 together means your charge voltages are fighting each other — AGM wants higher absorption, LiFePO4 hates it.

Cerbo GX is brilliant for monitoring but it won't solve the underlying chemistry mismatch, just lets you watch it happen in detail 😅

What I'd do: isolate them onto separate charge sources if you can. Even a basic DC-DC charger (Victron Orion-Tr is what I use) between them keeps things sane.

Longer term though — are the AGMs actually earning their keep? In my garden office setup I ditched my old AGMs pretty sharpish once the Fogstar cells were in. The capacity difference is night and day.

What's your actual use case? That changes the answer quite a bit.

Reply by Bazza49:

@HarbourKev Ha, classic forum cliffhanger — your post got cut off mate! Keen to hear the rest of your setup.

That said, I've been running a Cerbo GX with a mixed arrangement for about 18 months and the honest answer is: it depends entirely on whether you keep them on separate charge circuits. My AGMs and lithiums are on completely isolated banks with their own BMVs reporting back to the Cerbo. The GX handles the monitoring beautifully but it won't save you from a poorly designed charging setup underneath it.

The Fogstar Drifts are decent batteries btw — good choice. Main headache I found was getting the MultiPlus charge profile to keep both banks happy without compromising the LiFePO4 longevity. Ended up using two separate charge outputs. More wiring, but far less grief long-term.

Finish your post and we can dig into specifics! 👍

@HarbourKev yes, finish that sentence! Though I can probably guess where it's going.

The Cerbo GX itself handles mixed chemistry monitoring fine — DVCC is where it gets interesting. If you're running a shared BMS bus, the LiFePO4's BMS will almost certainly pull charge current down before your AGMs are fully satisfied, which progressively sulphates them.

My workaround on a similar setup: isolate the chemistries onto separate battery buses, each with its own MPPT (I've got two SmartSolar 100/30s), then let the Cerbo aggregate the data. You lose some simplicity but retain proper charge profiles per chemistry.

Longer term though — those salvaged AGMs are probably your weak link regardless. Worth load-testing them individually with a proper analyser before spending too much time optimising around them.

@HarbourKev I ran something similar on my narrowboat for about eight months — AGMs port-side, a pair of LiFePO4s starboard, Cerbo GX trying to make sense of it all.

Honestly the Cerbo itself isn't the headache. It's your charge sources that need attention. My MultiPlus nearly cooked the AGMs trying to top-charge the lithiums properly. In the end I isolated them onto separate charge circuits entirely and used the Cerbo's two-battery monitoring just to keep an eye on state of charge across both banks.

It works, but you're essentially managing two systems that happen to share a display. Whether that's "worth it" depends on how long those AGMs have left in them — mine gave up the ghost by winter anyway, which rather made the decision for me.

What's your charge setup — solar, alternator, shore power? Makes a difference to what approach is sensible.

@HarbourKev another cliff-hanger reply from @LazySocket too, this thread is cursed 😄

Running a Cerbo GX on my static van with Fogstar Drift cells and I'd say it's absolutely worth it, but you cannot treat mixed chemistry as a single bank — the Cerbo won't save you from yourself there. Keep them on separate charge sources with correct absorption/float profiles for each chemistry.

The real win is using VRM portal to catch drift early — you'll see immediately if your AGMs are dragging voltage down or your LiFePO4s are hitting BMS cutoff unexpectedly.

My setup: MultiPlus II handles the LiFePO4 bank via DVCC, AGMs on a separate Orion DC-DC. Cerbo ties the monitoring together beautifully but the wiring logic needs thinking through properly first.

What inverter/charger are you running?

Thread is full of cliffhangers today 😄

I've got a Cerbo GX on my shepherd's hut setup and honestly the mixed chemistry question kept me up for weeks before I just committed to separating them properly. Ended up using a Victron Orion DC-DC isolator between the two banks rather than running them in parallel — that way each chemistry charges at its own profile and the Cerbo monitors both banks independently via separate BMV-712s.

Not the cheapest solution but it's been solid for about 14 months now. The VRM dashboard actually shows it really clearly when the AGMs are being prioritised for bulk loads versus the LiFePO4s handling overnight draw.

The real headache is setting your charge parameters — you essentially have to pick the lowest common denominator if you do run them together, which means your lithium never gets what it wants.

Same here @Gill1982 — shepherd's hut and static both running Cerbo GX. Mixed chemistry is genuinely more trouble than it's worth in my experience. Ended up splitting them into separate banks with a Victron Orion DC-DC charger between them. Each bank gets charged properly for its chemistry rather than compromising both. The Cerbo monitors everything cleanly that way too — no weird SOC readings trying to reconcile two different voltage curves. Bit more wiring upfront but saved a lot of head-scratching. Wouldn't go back to trying to run them together.

Same situation on my shepherd's hut actually — Cerbo GX keeping an eye on everything.

The bit nobody mentions is the DVCC settings becoming a proper headache when chemistries don't agree on charge voltage. My AGMs wanted 14.4V absorption, LiFePO4s are happiest around 14.2V — sounds minor but over time the AGMs were getting slightly undercharged or the lithiums were taking a beating.

Ended up separating them onto different battery inputs with a Victron Orion between them. More wiring faff than I wanted but the Cerbo at least gives you decent visibility of what's actually happening across both banks.

Good timing on this thread — I went through exactly this last autumn. The Cerbo GX handles the monitoring of mixed chemistry well enough, but the real headache is that your charge profile has to compromise between the two chemistries. I ended up running the AGMs slightly undercharged to protect the LiFePO4s, which isn't ideal long-term for either bank.

@HarbourKev what's your charging source — solar, mains hookup, or both? That makes a big difference to how you manage it. Worth considering whether a separate charge controller dedicated to each bank is the smarter route rather than trying to balance everything through one system.