David's Thread on using YamBMS with a Deye inverter

Having run a Victron MultiPlus II with a DIY LiFePO4 pack for the past couple of years, I've been watching the Deye/YamBMS combination with considerable interest, particularly for a secondary setup I'm planning for my static caravan.

From what I can gather, YamBMS handles the CAN bus communication reasonably well once you've sorted the correct DIP switch settings on the Deye side — that seems to be where most people come unstuck. David, did you find the BMS was correctly reporting state of charge to the inverter, or were you seeing drift over time?

The bit that concerns me most for a backup/emergency application is how the system behaves during a comms dropout between the BMS and inverter. With Victron and their own ecosystem it's well documented, but I've struggled to find solid real-world data on Deye's fallback behaviour.

A few questions worth exploring in this thread:

• Which firmware version are you running on the Deye?
• Are you using the RS485 or CAN interface specifically?
• What cell configuration — 16S, 24S?

I'd also be curious whether anyone has tested this with Fogstar Drift cells specifically, as that's likely the route I'd take for the caravan build given the price point.

Keen to hear from others who've moved beyond the bench-testing stage and have this running in anger on a real installation. There's a reasonable amount of YouTube content floating about but precious little from UK installs with UK grid parameters properly configured.

@FormerTeacher61 really interesting thread — I've been eyeing up Deye inverters for a secondary setup myself, mainly because the price point is so much friendlier than adding another Victron to the mix.

Quick question though — how does YamBMS handle cell balancing communication with the Deye? With my current Victron/Fogstar setup the DVCC integration feels quite seamless, but I'm wondering whether the Deye interprets the BMS data as reliably, particularly around charge current limiting when cells start drifting?

Also, are you running this over RS485 or CAN bus? I've read conflicting things about which protocol gives you better visibility into the actual BMS state on the Deye side.

Would love to know if you've stress-tested it during a heavy EV charging session — that's really where I'd need it to hold its nerve. 🔋

@FormerTeacher61 the irony of spending months researching whether to trust a £800 Deye over your battle-tested Victron, only to end up buying both anyway, is not lost on me 🛶

@FormerTeacher61 ran a similar crossover evaluation last spring. The YamBMS/Deye integration isn't as plug-and-play as the marketing suggests — the CAN bus comms can be flakey depending on firmware versions, and Deye's documentation is frankly appalling compared to Victron's.

Key thing nobody mentions: the BMS charge/discharge limits don't always propagate correctly to the inverter under load transitions. Took me three weeks of logging with a Cerbo GX to even identify the issue.

For a secondary setup it's probably acceptable. For anything critical, the Victron ecosystem wins purely on support infrastructure and community knowledge. Victron's VRM portal alone is worth the premium.

What cell chemistry are you running in the DIY pack? JK BMS with Fogstar cells behaves quite differently to CATL-based builds under the same BMS configuration.

@SolarJunkie that matches what I found when setting up my garden office system. The CAN bus configuration with YamBMS needs more attention than the marketing suggests — particularly around the charge current limits not always being respected cleanly on the Deye side.

I'm still running Victron for my main setup and honestly wouldn't swap it. But for a lower-stakes secondary installation the Deye/YamBMS combo is workable once you've put the hours in.

One thing worth flagging: make sure your BMS firmware is current before you even start. I wasted a weekend chasing what turned out to be a known comms issue that was patched months prior.

@SolarJunkie @Louise1984 interesting points on the CAN bus headaches — had similar grief when I was sorting comms on my motorhome setup, though that was Victron kit rather than Deye.

One thing worth flagging for @FormerTeacher61: if this secondary setup is partly for emergency backup, the Deye's grid-tie focus can complicate things. Some models need a firmware tweak to behave properly in islanded/off-grid mode without the grid present. Worth confirming your exact Deye model supports seamless transfer switching before committing.

Has anyone tested the YamBMS SOC accuracy under heavy discharge loads? On my emergency backup rig I found BMS reported SOC can drift noticeably from real capacity during high-current draws — wondering if YamBMS handles that better than some of the cheaper options out there.