Battery Protect and anchor winch

Been thinking about this one for a while actually, as I've got a similar dilemma coming up with my van conversion build.

I'm running a 100Ah Fogstar Drift LiFePO4 and I want to add a small electric winch for recovering the van when I get myself into bother off-road. The winch pulls serious current in short bursts — we're talking potentially 100A+ — and I'm wondering how best to protect the battery without the BMS just cutting out at the worst possible moment.

A few questions for the group:

• Has anyone used a Victron Battery Protect in this kind of high-draw scenario? I know they're rated for continuous loads but I've read they can struggle with inductive loads like winch motors
• Would a low voltage disconnect relay be a better shout, wired directly off the BMS low-voltage signal?
• Is there a risk the BMS itself just trips the whole system before any external protection device even gets a chance to act?

The Fogstar BMS seems pretty capable but I don't fully understand how it interacts with sudden high-draw devices. In theory the Battery Protect should cut the load before the cells drop too low, but winch spikes are so brief and violent I'm not sure the voltage sag during a pull would even trigger it in time to matter — it'd recover the moment the load stops.

Anyone running winches or similarly aggressive loads off lithium in a van or off-grid setup? What protection method actually works reliably in practice rather than just on paper?

@StuKnight the issue with running a winch through a Battery Protect is the inrush current — those things spike massively on startup and the BP will likely trip or get damaged.

What I did on my van build was run the winch on a separate direct circuit from the battery with its own ANL fuse, completely bypassing the BP. The BP then handles all your leisure loads as normal.

Worth checking the Fogstar Drift's continuous discharge rating too — the Drift handles it fine but you want to make sure your cabling is sized for those peak winch amps rather than just the fuse rating.

A Victron Smart BatteryProtect is great kit but it's simply not designed for motor loads. Keep it for your 12v distribution and run the winch direct with appropriate protection.

@RayPowell is spot on about the inrush, and worth adding that Victron's own documentation actually explicitly states the Battery Protect shouldn't be used on inductive loads — winches, motors, compressors etc fall into that category. The back-EMF when the motor stops can damage the unit too, not just the startup spike.

What I'd suggest @StuKnight is keeping the winch on a completely separate circuit direct from the battery with its own fusing, and let the BMS on the Fogstar handle the protection side. The Drift's built-in BMS is reasonably capable for that sort of thing. Your Battery Protect can then do its job properly looking after your leisure loads without being hammered by the winch.

What sort of winch are you looking at? Rated pull will give us a better idea of the current draw you're dealing with.

@StuKnight I've got a Victron Battery Protect on my static van setup and learned the hard way — high-inrush loads like winches, compressor fridges, and inverters really shouldn't go through them. The BP uses a MOSFET switch that simply can't handle those spikes.

What I'd do is run the winch directly from the battery via a proper rated fuse and a heavy-duty relay or contactor, then trigger that relay through a separate low-current circuit. Keeps your Battery Protect doing what it's actually designed for — protecting against over-discharge on your leisure loads.

A 100Ah Fogstar Drift has a decent continuous discharge rate but check the peak spec before sizing your winch anyway — you want to make sure the BMS won't trip under load either.

@StuKnight worth looking at a proper DC contactor or solenoid relay rated for the winch load instead — bypass the Battery Protect entirely for that circuit. Run the winch direct from the battery with its own fuse, then let the Battery Protect handle everything else.

On my motorhome I've got a similar split setup — high-draw stuff like the compressor fridge starter surge goes round the BP, not through it. Keeps everything happy.

Fogstar Drift has decent continuous discharge anyway so the battery itself should handle a small anchor winch no bother — it's just about protecting the BP from seeing that inrush @RayPowell mentioned.

What size winch are you looking at? That'll determine what contactor rating you need.