Anyone else had issues with JBD BMS dropping out at low temps this winter?

Been running a 200Ah lithium setup in my van (4x 50Ah EVE cells in series) with a JBD 100A BMS, and I've noticed it's been tripping out on cold mornings — we're talking anything below about 4°C here in Scotland. It'll disconnect the load entirely, which then kills my 12V fridge and woke me up at 3am the other night to a very warm curry situation. Not ideal.

I've had a look through the BMS settings via the Xiaoxiang app and I'm not entirely sure whether it's the low-temp discharge protection kicking in or something else. The threshold was set to 0°C when I first checked it, which should be fine for 4°C ambient, but I've got the temperature sensor gaffer-taped to the side of one of the middle cells so I'm wondering if that's giving a dodgy reading. Anyone know what the actual cell temperature tends to be versus ambient when the van's been sitting overnight with no charge going in?

Has anyone physically relocated their temp sensor or added a second one for more accurate readings? I've seen a few people mention putting it between two cells rather than on the outside, but I don't want to go poking around in there and void anything if there's a simpler fix first.

PaddyFox | 847 posts

@CallumHamilton83 Yes, classic JBD behaviour this — the low temperature charge protection kicks in around 5°C on most of their units by default. Worth connecting via the Xiaoxiang app (free on Android) and checking your "Low Temp Charge Protection" threshold settings. You can dial it back a few degrees if your cells can genuinely handle it, though I'd be cautious pushing it too far with EVE cells in a van environment where temps can drop sharply overnight.

The other thing worth checking is whether it's actually the charge protection or a low temp discharge cutoff triggering — they behave quite differently. What's your charging source when it trips — solar, alternator, or mains? That'll help narrow it down.

@CallumHamilton83 this is almost certainly the low-temperature charge protection cutting in — JBD's default settings are typically around 5°C charge cutoff, which matches your symptoms exactly.

On my narrowboat I had identical behaviour last January. The fix that worked for me was twofold:

1. Adjust the BMS parameters using the Xiaoxiang app — you can lower the charge cutoff to around 0°C if your cells are genuine EVE grade A (they handle it better than the spec sheet suggests)
2. Add a temperature sensor to the actual cells rather than relying on ambient — the BMS is probably reading air temp, not cell temp, so it's tripping prematurely

Worth also checking whether it's actually the BMS tripping or your charger entering protection mode independently. What's your charging source — solar, alternator, shore power?

Has anyone actually tried adjusting the low-temp charge protection thresholds via the Xiaoxiang BMS app? I've got a similar EVE cell setup in my van and I'm wondering whether bumping the cutoff down to say 0°C (rather than the default 5°C) is actually safe, or whether charging LiFePO4 cells even slightly below freezing risks plating the anodes.

Also curious — is this purely a charging issue or can the BMS drop out during discharge too at low temps? Mine's been doing something similar on frosty mornings and I can't tell whether it's the charger triggering the protection or something else entirely.

Nobby | 134 posts

Slightly different context from you lot (garden office rather than a van) but I had almost identical dropouts last January with a JBD 200A unit.

Quick question for anyone who's adjusted those thresholds — does lowering the low-temp cutoff actually risk damaging the cells, or is JBD just being overly conservative from the factory? I'm wary of just disabling the protection entirely.

Also @VanLee — did you find the Xiaoxiang app reliable for saving those settings, or do they revert after a power cycle? Mine has occasionally forgotten config changes which makes me nervous about depending on it.

Currently I'm just using a small 12V heat mat under the battery box triggered by a cheap thermostat probe, which seems to work but feels like a bodge compared to sorting the BMS settings properly.

Wrap your cells in closed-cell foam — sorted mine on the narrowboat overnight, temps were brutal last January and the JBD never blinked after that. Low-temp cutoff is doing its job protecting the cells from charge damage, so don't just disable it; insulate first, then tweak thresholds if still needed. Fogstar cells are pretty tolerant but lithium charging below freezing is genuinely asking for dendrite trouble. @VanLee the Xiaoxiang app is fine for threshold adjustments but don't go lower than 0°C for charge protection unless you're also adding a heating element — a cheap self-regulating heat mat from Amazon running off a small 12V supply does the trick nicely.

Good shout from @EssexNomad on the insulation — done similar on my static with 25mm Kingspan around the battery box, makes a real difference overnight.

One thing nobody's mentioned: check your low temp charge cutoff setting isn't too conservative. JBD defaults can be quite cautious — mine was set to 5°C from factory. Bumped it down to 2°C (lithium can technically charge down to ~0°C at reduced rates) and the nuisance trips stopped.

Also worth adding a small self-heating mat if it keeps being a problem — 12V reptile mats off Amazon work a treat and barely touch your capacity.

DebbieEvans | 287 posts

@CallumHamilton83 worth checking whether it's actually the low-temp charge protection cutting in or the low-temp discharge protection — they're separate settings in the Xiaoxiang app and have different default thresholds. Mine was tripping on discharge protection at around 5°C which caught me right out initially.

Also, are you using any heating in the van overnight? A small self-regulating heat mat (the silicone type rated for lithium) tucked between the cells made a noticeable difference for me last winter in terms of keeping temps above the threshold. Just make sure you're not covering ventilation if your setup needs it.

What are your current protection settings actually showing in the app? That'd help narrow down whether it's a settings tweak job or a proper thermal management problem. 🙂

@DebbieEvans makes a crucial point — worth pulling the BMS parameters with the JBD app and checking your low-temp charge cutoff threshold specifically. On my narrowboat setup I found the default firmware had this set at 5°C, which is conservative but not unreasonable for EVE cells.

What I'd add: check whether you're seeing a charge cutoff or a discharge cutoff — they're separate protection circuits with different thresholds. The JBD app will show you live cell temps alongside the event logs, so you can pinpoint exactly which protection triggered. If it's discharge cutting out at 4°C that's a potential firmware misconfiguration worth investigating.

TimGreen | 412 posts

Just to add a practical angle here — I had almost identical symptoms last January in my workshop setup. Even after sorting the BMS parameters as @SunnyDrifter mentions, I found the cells themselves were sitting cold enough that internal resistance had spiked noticeably, which was triggering overcurrent protection before the temp cutoff even kicked in. Worth doing a quick voltage check under load on a cold morning to see if you're getting sag that wouldn't appear at normal temps. A small ceramic heater on a timer set to kick in an hour before you typically start drawing load made a real difference for me.

WendyLewis | 634 posts

@CallumHamilton83 One thing nobody's mentioned yet — if you're running the battery in an uninsulated part of the van, the cell temperature can be several degrees lower than ambient, so even on a 4°C morning your cells might actually be sitting at 1–2°C when the BMS reads them. A simple fix that helped me enormously was wrapping the battery in closed-cell foam camping mat material. Cost me nothing and kept my cells a good 3–4 degrees warmer overnight. Combine that with what @DebbieEvans and @SunnyDrifter suggested about checking your charge parameters and you should have a clearer picture of what's happening.