Anyone else running LiFePO4 on a narrowboat? Curious about BMS behaviour at low temps

I've just finished swapping out the old AGM bank on my 57ft narrowboat for a 200Ah LiFePO4 setup — 4 x 50Ah cells in parallel, with a Daly 100A BMS. Charging comes from a 200W solar panel on the roof and a Victron Orion-Tr Smart 12/12-18 for alternator charging off the Beta 43. All seemed fine over summer but now it's getting colder I'm noticing the BMS is cutting out on charge occasionally, presumably because it's hitting the low-temperature protection threshold.

The battery bank lives in the engine bay which I thought would stay reasonably warm, but overnight it's clearly dropping below whatever the Daly is set to (I think around 5°C from the factory). I'm not keen on disabling the protection entirely — that feels like asking for trouble — but I also don't want to miss charging hours on grey winter days when the boat's just sitting on a mooring.

Has anyone added a thermostat-controlled heat mat or wrap to their cells to deal with this? I've seen a few setups using a small self-regulating heating pad wired to cut in below a set temp, but I'm not sure what to use as the power source for the heater overnight when solar isn't generating. Would a small trickle from the starter battery via a relay make sense, or is that just creating a new problem?

Also interested whether anyone's adjusted the low-temp cutoff on a Daly BMS — I've seen references to the PC software tool but I can't find clear instructions for the specific settings.

ColJames74 | Posts: 847

@BordersSolar nice upgrade! One thing worth knowing with the Daly specifically — the low temp cutoff kicks in around 0°C and will simply disconnect charging, which can catch you out on a cold morning when you're expecting the solar to be topping things up. The cells themselves are fine to discharge in the cold, just not to charge.

Worth considering a small self-regulating heat mat under the battery box if you're planning winter liveaboard use — draws very little and keeps things above that threshold. I've seen a few boaters get caught out moored up in January wondering why their panels aren't doing anything!

What inverter/charger are you running alongside the solar? That'll affect how your BMS behaves under load as much as anything.

@BordersSolar worth knowing that LiFePO4 chemistry becomes genuinely problematic below around 0°C — not just degraded performance, but actual lithium plating on the anode during charging, which is permanent damage. The Daly BMS should cut charging at low temps if you've set the parameters correctly, but I'd verify what threshold yours is configured to.

On a narrowboat you're likely mooring in ambient temps that'll drop below that threshold overnight in winter. Consider whether your battery compartment has any thermal mass from the boat's interior warmth, or whether it's an exposed bow/stern locker.

In my van conversion I use Fogstar Drift cells which have built-in self-heating, but that's obviously a different form factor. For a narrowboat install, some people run a small thermostatically-controlled heat mat underneath the bank — cheap insurance against a ruined cell.

LesCrane90 | Posts: 312

@BordersSolar great setup! Just to add to what @ColJames74 was getting at — LiFePO4 cells really don't like being charged below about 5°C, even if they'll happily discharge in the cold. The Daly BMS should cut charging at low temps but I'd double-check yours actually has the temperature sensor connected properly, as some arrive with it just tucked loose in the box rather than fitted to the cells. Worth taping it directly onto one of the middle cells with some thermal paste.

On a narrowboat you've also got the advantage that the engine bay stays fairly warm when you're cruising — might be worth thinking about where your bank is physically located. Mine's under the dinette and rarely drops below 8°C even in January. What's your installation spot like?

MuddySkipper | Posts: 43

@BordersSolar interesting setup — I've been looking at something similar for a garden office install (land-based, I know, but the BMS behaviour questions are the same).

One thing I haven't seen mentioned: have you confirmed whether your Daly BMS has low-temperature charge cutoff enabled? Some units ship with it disabled by default. Worth checking via the Daly app if you haven't already.

Also curious — what's your charging source doing when the BMS trips? Does the Daly communicate anything back to your charge controller, or does it just hard-disconnect and leave your panel voltage floating? That interaction seems like it could cause issues over a prolonged cold mooring.

Are you planning any insulation around the battery bank itself? Even wrapping the cells helps slow the temperature drop overnight.

ValleyNomad | Posts: 187

@BordersSolar nice one, that's a solid setup for a 57-footer. One thing worth flagging that I haven't seen mentioned yet — with a Daly BMS specifically, the low-temp charging cutoff protection is sometimes inconsistent or absent on cheaper units. Worth checking your exact model's spec sheet rather than assuming it's covered.

I'd strongly recommend picking up a cheap battery temperature monitor if you haven't already. Running through a cold snap on the cut last winter taught me that bilge temperatures can drop surprisingly fast overnight, especially if you're moored up and not running the stove. Even a basic alert giving you a heads-up before things get marginal is worth its weight. Some folks also wrap cells in a bit of insulation — nothing fancy, just keeps ambient temps more stable.

How are you finding charge times on 200W solar this time of year? Must be pretty limited.