Projet de mixage Pylontech et Lifepo4

Has anyone here successfully mixed battery brands on a Victron/Cerbo GX setup?

I've got a couple of Pylontech US3000C units on my cabin system running ESS, and I'm seriously considering adding a custom LiFePO4 pack alongside them. The Pylontechs talk to the Cerbo natively via CAN bus, which is brilliant — but I'm wondering how the Cerbo handles a second battery with its own separate BMS that doesn't speak the same protocol.

From what I can tell, the Cerbo GX will only recognise one "managed battery" system at a time. So if I bolt on a Fogstar-celled DIY pack with, say, a JK BMS set to communicate via a different interface, does the Cerbo just ignore it entirely? Or does it throw errors and mess with the charge logic for the Pylontechs too?

A few specific questions I can't find clear answers to:

• Can you run a second battery purely in parallel at the DC busbar level, letting the Pylontechs handle all the BMS communication, with the second pack essentially "invisible" to the Cerbo?
• Is there a risk the Pylontech BMS gets confused by the extra capacity it doesn't know about?
• Has anyone used a Victron SmartShunt on the secondary pack as a workaround to at least monitor it separately?

I realise mixing managed and unmanaged batteries isn't ideal, but the economics of adding more Pylontech capacity right now are pretty grim. The DIY route looks tempting.

Would love to hear from anyone who's actually done this rather than just theory — boat or off-grid cabin setups especially relevant.

@Cerbo_Queen the thread title's in French but I'll answer in English 😄

Short answer: don't mix brands if you can help it. Pylontech have their own BMS with very specific charge/discharge curves. Lumping custom LiFePO4 cells alongside them without matching internal resistance and capacity is asking for trouble — one bank will always work harder than the other.

If you're dead set on expanding, just add another US3000C or step up to US5000. Pylontech stack nicely and the Cerbo picks them up automatically via CAN.

Custom cells can work in a separate bank with their own BMS (Daly or similar), connected as a second battery system — but that complicates your ESS config considerably.

Done it the wrong way once. Ended up with a very unhappy BMS and a wasted weekend.

@Cerbo_Queen backed up my whole house setup with a pair of Pylontechs for exactly this reason — mixing chemistries (even same chemistry, different brands) causes the BMS units to fight each other over charge thresholds. Your Cerbo will struggle to reconcile conflicting CAN bus comms from two different BMS protocols.

If you're dead set on expanding, just add another US3000C. Fogstar do decent pricing on Pylontech right now.

If budget's tight, sell the Pylontechs as a matched pair (they hold value well) and start fresh with whatever you want.

@Cerbo_Queen I'd echo the caution others have raised, but worth adding — even within same chemistry LiFePO4, mismatched capacity and internal resistance between brands can cause the BMS units to fall out of sync during charge/discharge cycles. The Cerbo GX handles multi-battery comms reasonably well via DVCC, but it's essentially trying to referee two systems with different opinions about SOC.

What's the specific brand you're looking at adding? Some third-party LiFePO4 units play nicely if you can force them onto the same CAN bus protocol, but honestly the path of least resistance is sticking with Pylontech and grabbing another US3000C or stepping up to a US5000. Second-hand US3000Cs have come down quite a bit lately if budget's the concern. 🙂

Same boat here (literally — narrowboat setup). Tried mixing a Fogstar Drift with an older unit once and the BMS communication was a nightmare. Cerbo couldn't balance them properly and one bank kept getting babied while the other worked too hard.

Pylontechs talk to Victron natively via CAN bus — that's a big part of why they work so well. Throw in a custom pack with different internal resistance and you're asking for grief, even if the voltage specs look identical on paper.

If you need more capacity, just add another US3000C. They stack cleanly and the Cerbo recognises them without fuss.