How to charge the WattCycle 16kWh 48V 314Ah Floor Standing Battery

Picked one of these up last month for the garden office and honestly it's been a treat — the built-in BMS is surprisingly sensible about not letting you do anything catastrophically stupid, which is more than I can say for myself at 11pm trying to wire things up by torchlight.

For charging, mine's running off a Victron MultiPlus-II 48/3000 and the sweet spot I've found is:

• Bulk/Absorption: 54.4V (matching the 3.4V/cell LFP target)
• Float: 53.6V — don't let anyone talk you into leaving it at full charge constantly, your cycle life will thank you
• Max charge current: I'm keeping it under 100A, though the unit can take more

The WattCycle app actually gives you the recommended parameters in the settings menu, which is refreshing compared to some batteries that arrive with a photocopied A4 sheet and a vague sense of dread.

If you're coming from a Fogstar or similar, the charge profile is essentially identical — standard LFP, nothing exotic.

One thing worth flagging: don't mix this with an MPPT set to AGM profile unless you enjoy warranty-voiding adventures and a very awkward phone call.

Anyone else running theirs with a different inverter-charger? Curious whether the Renogy RBC50 plays nicely with it or if there are quirks — my neighbour's eyeing one up and I'd rather he asks here than rings me at the weekend again. 🔋

Stick a Victron Multiplus on it and let the BMS argue with the charger like an old married couple until they sort themselves out — worked a treat on my static van setup.

Great shout @LazyRanger, I've got a similar setup running in my workshop. One thing worth mentioning that nobody's touched on yet — make sure you're setting your charge voltage to 54.4V (that's your 3.45V per cell for 16S LiFePO4) rather than letting any charger default to a generic lithium profile. The WattCycle's BMS will tolerate a bit of slop but you'll get better cycle life keeping it disciplined. Also worth checking the low-temp cutoff settings if you're heading into autumn — garden offices can get properly cold overnight and LiFePO4 really doesn't want to be charged below about 5°C. The BMS should handle it but I've seen them vary on how conservatively they're configured from the factory.

Following on from what @EwanScott was about to say (the suspense is killing me, finish your sentence mate) —

One thing I've been wondering with these floor-standing units: what's the recommended absorption voltage from the BMS comms? My shepherd's hut runs a Victron MPPT into a more modest setup, but I'm eyeing one of these for a cabin project and the 48V charging profile seems to vary wildly depending on who you ask.

Specifically:

• Does the BMS broadcast a fixed absorption voltage or does it negotiate dynamically?
• Is anyone using DVCC in Victron OS to let the battery take the wheel entirely?

The manual for these Chinese units tends to read like it's been translated via three languages and a fever dream, so real-world numbers from someone actually running one would save me considerable head-scratching.

Right, I'll chip in here as someone who spent 35 years wrestling with systems that absolutely did not want to cooperate with each other.

@Moorey40 is spot on about the Multiplus pairing, but make sure you've got your absorption voltage set correctly for LiFePO4 — a lot of folk leave it on the AGM preset and wonder why the BMS keeps kicking the charger off. Should be sitting around 54.4V for a 48V lithium pack, float somewhere around 53.6V or just disabled entirely really.

Also worth checking whether your WattCycle has the CAN bus port active — if it does, proper DVCC communication through a Cerbo GX will sort out a fair chunk of the charging arguments @Moorey40 mentioned. Lets everything talk properly rather than guessing at each other.