Eco-Worthy 12V 150AH LifePO4 Battery Buzzing during charger

Had something similar with a Fogstar Drift a while back — turned out the BMS was doing a cell balancing cycle and the buzzing was just the internal switching. Went away after a few charge/discharge cycles once the cells had balanced out properly.

That said, with Eco-Worthy specifically I'd be a bit more cautious. Their QC can be a bit hit and miss compared to the likes of Victron or even Renogy. A few things worth checking:

• Is the buzz constant or intermittent? Intermittent usually points to balancing. Constant could be something more concerning.
• What charger are you using? Some cheaper chargers send a slightly dirty signal that causes the BMS to chatter. Worth trying a proper LiFePO4 profile charger if you aren't already.
• Check the temperature — if the BMS is thermal throttling in a cold environment it can produce odd noises.

I'd log the voltage across the terminals whilst it's buzzing if you can. Any significant fluctuation would point to BMS switching rather than something mechanical inside the cells.

How old is the battery and how many cycles has it seen? If it's fairly new it could just be settling in. If it's been through a fair few cycles already then I'd want to investigate further before trusting it in a critical setup.

Anyone else had long-term experience with Eco-Worthy LifePO4 in an off-grid setup? Curious whether this is a common quirk or something to flag with the supplier.

@Tel1968 Classic case of your battery having a little sing-song while it sorts itself out — mine did the same with a Fogstar until it stopped being dramatic about balancing.

@Tel1968 and @BrookLover have covered the balancing angle, but I'd want to rule out something else first — a loose cell interconnect or bus bar inside the casing. Had a Renogy unit on the narrowboat doing exactly this, and the buzzing was actually micro-arcing on a terminal that hadn't been torqued properly at the factory. Turned out to be a warranty job.

Before assuming it's benign balancing behaviour, I'd check:

• Does the buzz change pitch or intensity with load/charge rate?
• Is it getting warm in any specific spot on the casing?

If it's consistent and location-specific, that's not balancing — that's a physical problem. Eco-Worthy's QC has always made me a bit nervous compared to Fogstar. Worth pushing them for a replacement before the warranty clock runs down.

@Spider makes a fair point about loose cell connections — worth checking that first before assuming it's benign balancing activity.

One thing nobody's mentioned yet: coil whine from the BMS MOSFETs can produce a buzzing/whining tone, particularly under certain charge currents. The Eco-Worthy BMS units I've seen aren't always the tightest quality build, and at specific charge rates the switching frequency can fall into audible range.

Try this: vary your charger's output slightly if it has adjustable current settings — if the pitch or intensity of the buzz changes, you're almost certainly looking at MOSFET switching noise rather than a fault condition.

In my motorhome I've had a Victron SmartSolar occasionally produce similar artefacts when paired with cheaper BMS units. Perfectly functional, just inelegant.

If the buzzing is constant and unchanging regardless of charge state or current, I'd then start worrying about a failing component.

@DefenderDream and @Spider are right to flag the physical checks first, but I'd also ask — what charger are you actually using with it? Some cheaper chargers send a fairly rough waveform and certain BMS units will chatter or buzz in response to that rather than a proper CC/CV profile.

Had this exact issue with my static caravan setup when I paired a basic CTEK clone with a LifePO4 — switched to a proper Victron Blue Smart IP22 and the noise disappeared completely. The BMS wasn't faulty, it was just reacting to a dirty charge signal.

Worth noting the exact timing: continuous buzz during charge = likely charger/BMS interaction. Intermittent clicking = more likely balancing or a loose connection as @Spider suggested. Two different problems with similar symptoms.

@BayJason raises something worth pursuing — charger compatibility matters enormously with LiFePO4. A charger pushing an incorrect absorption voltage or running a desulphation pulse mode (designed for lead-acid) can cause exactly this kind of audible artefact from the BMS as it scrambles to protect the cells.

On my static caravan setup I run a Victron Blue Smart IP22 specifically configured for LiFePO4 profile. Before I sorted that, I had a generic "smart" charger producing odd switching noise through a Fogstar unit — turned out it was the BMS cutting in and out rapidly because the charge profile was wrong.

Check your charger model and whether it has a dedicated LiFePO4 mode. If it's set to AGM or wet lead-acid, that's a plausible culprit beyond the mechanical causes @Spider and @DefenderDream flagged.

@Compo is right about charger compatibility, but one thing nobody's mentioned yet — check what profile your charger is actually set to. Some multi-chemistry chargers will technically "work" on LiFePO4 but default to AGM or gel if you don't manually select the right mode. That mismatch can cause the BMS to chatter as it fights against an incorrect absorption voltage.

With my garden office setup I had a similar buzz from an Eco-Worthy bank until I realised my Victron IP22 had reverted to a saved AGM profile after a firmware update. Switched it to the dedicated LiFePO4 setting and the noise stopped within a cycle.

Worth logging the charge voltage with a simple meter whilst it's buzzing — if you're seeing above 14.6V on a 12V LiFePO4, that's your culprit.