Swapped to a 200Ah lithium setup in my Transit — anyone else notice the BMS cutting out when it's cold?

Been running a 200Ah lithium setup in my Transit for about six months now and the cold weather has been causing me some headaches. The BMS keeps tripping out when overnight temps drop below about 4°C — woke up twice last week with a completely dead van and couldn't charge the battery at all until it warmed up a bit in the morning sun.

I'm using a Fogstar Drift 200Ah which I know is supposed to have low-temp protection built in, and I understand why it cuts off (lithium cells don't like being charged below freezing — fair enough), but it's caught me off guard more than once.

A few things I'm wondering:

• Has anyone found a practical workaround for winter use? Some sort of battery heating pad perhaps?
• Does the discharge cutoff kick in at a different temperature to the charge cutoff? Mine seems to still power loads fine when cold, just won't accept charge
• Would a self-heating lithium battery like the newer Fogstar or certain Renogy cells actually be worth the premium?

The main frustration for me is around EV charging — I've got a small inverter setup for topping up my PHEV from the van battery overnight on sites without hookup, and if the BMS cuts out mid-charge it throws everything out of sync.

Curious whether others running Transit or Sprinter setups have hit the same wall this winter and what you've done about it. Feels like something nobody really warns you about when you're buying into lithium over AGM.

@NeilEdwards classic cold-weather BMS behaviour — most lithium cells (particularly LFP) have low-temperature charge protection built in, typically cutting charging below 0–5°C to prevent plating on the anode, which causes permanent capacity loss.

The BMS isn't faulty; it's doing exactly what it should.

Practical fixes:

• Fogstar Drift cells have slightly better low-temp tolerance than cheaper alternatives
• Fit a self-heating battery (Fogstar do a 12V self-heating LFP) — draws a small discharge current to warm cells before allowing charge
• Insulate your battery compartment properly; even 25mm Kingspan makes a significant difference in a Transit
• Set your Victron MPPT to include a low-temperature charge cutoff in tandem with BMS protection

I've got my garden office battery in an insulated enclosure with a small 40W reptile heat mat on a thermostat — keeps it above 8°C all winter without significant parasitic draw.

@NeilEdwards the bit @DodgyRoamer hasn't finished saying is that LFP cells genuinely cannot safely accept charge below 0°C without causing lithium plating on the anode — permanent, cumulative damage. The BMS cutting out is actually doing its job properly.

What you want is a battery with built-in low-temperature charge cutoff and a self-heating function — Fogstar Drift cells are worth a look for van use, as is anything running a Daly or JK BMS with the heating pad option.

In my static caravan setup I run a Victron SmartShunt with temperature compensation configured, plus a small self-adhesive heater mat wired to a thermostat on the battery bank. Sorted the problem completely.

The real question is — what brand cells are in your 200Ah pack? That'll determine whether you've got a firmware/settings fix available or whether you're looking at hardware changes.

Heated battery blanket sorted this exact problem on my narrowboat last winter — wrap it up, job done, though admittedly my Fogstar cells now have a warmer social life than I do.

@NeilEdwards worth mentioning that even if you sort the charging side, discharge can also get sluggish in the cold — you'll often see a noticeable voltage sag under load when temps are low, which can trigger low-voltage cutoffs even on a battery that's reasonably full. Not dangerous like cold charging is, just frustrating.

One thing I'd add to what @OffGridJulie said about blankets — a small self-regulating heat mat wired to a thermostat works a treat and uses minimal power. Mine kicks in around 5°C and keeps the bank above the danger zone without running all night unnecessarily. Some of the better BMS units also have a low-temp charge lockout with a sensor input you can pair to a heating circuit directly. Might be worth checking what your BMS actually supports before spending money on workarounds.