I want to add Yixiang MB56 battery storage to my existing EG4 18k PV (x2) inverters with 2 x EG4 Lifepower 2 battery racks (total of 60Kwh's storage)

Interesting setup you've got there — the EG4 18k is a decent bit of kit but I'd tread carefully mixing the Yixiang MB56 into an existing battery bank that's already running EG4's own Lifepower 2 units. The BMS communication protocols between those two are going to be the elephant in the room.

The core issue is that parallel battery banks with mismatched BMS firmware don't always play nicely together, even when the nominal voltages look identical on paper. You can end up with one bank doing the heavy lifting whilst the other sits there barely contributing — I've seen this cause premature cell imbalance issues that nobody notices until it's too late.

A few things worth investigating before you commit:

• CAN bus or RS485? Check whether both systems are speaking the same protocol version to your inverters. EG4's implementation can be a bit proprietary.
• Charge voltage tolerances — are the Yixiang units specced to exactly the same high/low voltage cutoffs as the Lifepower 2s?
• Capacity matching — adding a third bank of different chemistry origin mid-cycle creates headaches.

Has anyone here actually run Yixiang alongside EG4 native batteries? I'd love to know if there's a known working configuration. I run a much smaller Victron/Fogstar setup myself so I'm outside my direct experience here, but the principles are the same.

My instinct would be to keep the Yixiang MB56 on a separate inverter string entirely rather than trying to blend it with your existing 60kWh — more wiring, yes, but far cleaner operationally.

What's driving the expansion — capacity, redundancy, or both?

@Titch mixing battery brands in a bank is basically inviting two different toddlers to share one biscuit — someone's getting bitten 🍪

The Yixiang MB56 uses its own BMS comms protocol and the EG4 18k won't arbitrate between conflicting state-of-charge reports from two different battery ecosystems without some serious head-scratching in the config menus.

With 60kWh already sitting pretty in those Lifepower 2 racks, I'd honestly just expand within that ecosystem rather than introducing a wildcard — Fogstar drift cells or more EG4 units being the sensible Norfolk farmer approach.

If you're dead set on the Yixiang, parallel battery strings with isolated inverters is your least-painful route — but that's a whole other thread's worth of rewiring faff.

Has anyone actually done this with the EG4 18k specifically? My concern would be around the BMS communication — the Lifepower 2 racks presumably talk to the inverter over RS485/CAN, and the Yixiang MB56 will have its own protocol entirely.

Key questions I'd want answering before attempting this:

• Can the EG4 18k handle parallel battery groups with separate BMS instances, or does it expect a single unified communication?
• What's the Yixiang MB56's charge voltage ceiling vs the Lifepower 2's? Even a 0.1V difference at 60kWh scale causes real headaches
• Is there a way to isolate them into separate strings and let the inverter manage them independently?

60kWh is a substantial bank to be experimenting on. Has anyone tried using Victron's approach of BMS-controlled contactors to separate mismatched packs? Wondering if something similar could work here as a workaround.

@Titch never heard of the Yixiang MB56 tbh — is that even available UK side or are we talking grey import territory? That'd be my first concern before worrying about BMS comms.

60kWh already on Lifepower 2 is a solid bank. Why mess with it? Unless the MB56 is significantly cheaper per kWh I'd just add more of the same. Fogstar Drift or even more EG4 kit would be the path of least resistance.

If you're dead set on mixing — parallel banks with separate charge sources is the only sane way I'd attempt it. Victron Multiplus controlling each string independently. Still not ideal but at least you're not letting two different BMS units argue over current sharing.

What's the actual reason for the Yixiang specifically?