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Cold is the silent killer of van batteries. LiFePO4 cells physically cannot accept charge below 0°C — the BMS locks out charging to prevent permanent lithium plating damage. AGM batteries lose up to 40% of their usable capacity at freezing temps. Winter demands a different approach.
The numbers: at -10°C, a LiFePO4 delivers only 70-75% of its rated capacity. That 200Ah bank is effectively 150Ah. Discharge still works — it's charging that's dangerous below 0°C. Most BMS units cut off charging at 0 to 5°C. If your solar starts producing at 8 AM but your battery compartment is -3°C, that energy goes nowhere until things warm up.
⚡ Expert tip
The cheapest battery protection in winter isn't heating — it's parking strategy. Park facing south so the sun hits your panels and warms the roof early. Park against a building wall for wind protection. Run your diesel heater for 30 minutes before sunrise to warm the interior (and battery compartment) before solar charging starts.
Example calculation for your setup
Results based on a typical use case
| Appliance | Power | Usage/day | Wh/day |
|---|---|---|---|
| Compression fridge | 45W | 24h | 1080 |
| LED lighting | 20W | 4h | 80 |
| Water pump | 30W | 0.5h | 15 |
| Phone charging | 15W | 2h | 30 |
| Daily consumption | 1205 Wh | ||
Recommended LiFePO4 battery
126 Ah
(80% depth of discharge)
Recommended AGM battery
201 Ah
(50% depth of discharge)
Adjust these values with the calculator below
VANPOWERCALC PROYOUR ENERGY PROFILE
YOUR ENERGY PROFILE.
This document contains the sizing of your future electrical installation, calculated based on your appliances.
Minimum Daily Consumption
0 WH / DAY
Inventory:
SYSTEM SIZINGPage 2
Battery
To guarantee 0WH without damaging your bank (80% max discharge):
0 AH
LiFePO4 12V
Solar
Minimum power required to recharge your consumption:
0 W
via MPPT
220V AC
Maximum power (with 25% safety margin).
0 W
No Need
Safety & CablingPage 3
12V Cable Sizing Guide
Use this professional reference table to select the correct gauge (mm²) for your cables. For 12V in a van, the maximum tolerated voltage drop is 3%. Always use multi-stranded flexible automotive wire.
| Current (A) | Round trip < 2m | Round trip 4m | Round trip 6m |
|---|---|---|---|
| 5A (LEDs, USB) | 1.5 mm² | 2.5 mm² | 4 mm² |
| 10A (Fridge, Pump) | 2.5 mm² | 4 mm² | 6 mm² |
| 20A (Heater) | 4 mm² | 10 mm² | 10 mm² |
| 50A (DC/DC Booster) | 10 mm² | 16 mm² | 25 mm² |
| 100A (Inverter) | 25 mm² | 35 mm² | 50 mm² |
Fuse Sizing
The fuse protects the wire, not the appliance. Always place it as close to the power source as possible (battery or busbar).
- Wire 1.5 mm² → Max fuse 10A
- Wire 2.5 mm² → Max fuse 20A
- Wire 4 mm² → Max fuse 30A
- Wire 6 mm² → Max fuse 40A
- Wire 10 mm² → Max fuse 60A
SCHÉMA ÉLECTRIQUE
PANNEAUX SOLAIRES
0W
REGULATEUR MPPT
BATTERIE AUXILIAIRE
0 Ah
Lithium LiFePO4
FUSIBLE
FUSIBLE
BOÎTE À FUSIBLES 12V
Pompe, Leds, Frigo...
CONVERTISSEUR 220V
NON REQUI
PRO GEARPage 4
SHOPPING LIST
Where to find this equipment? Here is the community-approved selection.
12V 6-way Fuse Box
Mandatory protection
Digital Multimeter
Test your connections
Heavy Duty Crimping Tool
For perfect lugs
Heat Shrink Tubing
Insulation and safety
GENERATED BY VANPOWERCALC PRO - UNLIMITED.
About this tool
Three tiers of winter protection, from cheapest to best. Tier 1: insulation. Wrap your battery compartment with 20-30mm XPS foam board on all sides. Cost: $15-20. This doesn't prevent freezing but slows heat loss dramatically — your battery stays above 0°C until late morning instead of dawn, buying hours of charging window. Tier 2: self-heated batteries. SOK, Epoch, and some Victron models have internal heating pads that activate at 5°C and warm the cells before allowing charge. Adds $100-200 to battery cost but it's the most foolproof solution. The heater draws 40-80W for 15-30 minutes. Tier 3: DIY heating pad + thermostat. A 50W silicone heating pad ($15) with a $10 thermostat (set to 5°C) runs only when needed. Total cost: $25-30 in parts. I've used this setup through two Alpine winters and it works perfectly. The pad draws less energy than you'd think — it only cycles on during the coldest pre-dawn hours.
Frequently asked questions
Can I charge LiFePO4 below freezing?▼
No. Charging below 0°C causes lithium plating — permanent, irreversible damage to the cells. Most BMS systems block charging below 0-5°C automatically. Discharging is fine down to -20°C, just with reduced capacity.
How much capacity does a van battery lose in cold weather?▼
LiFePO4 loses 25-30% at -10°C (200Ah becomes ~150Ah usable). AGM is worse — up to 40% loss at 0°C. Both recover full capacity once warmed. The capacity isn't destroyed, just temporarily reduced.
Do I need a heated battery for winter van life?▼
For occasional cold weather: insulation alone is usually enough. For serious winter camping below -10°C: yes, either buy a battery with built-in heating (SOK, Epoch) or add a DIY silicone heating pad with thermostat. The $25 DIY solution works just as well as the $200 built-in option.
How do I insulate my van battery?▼
Wrap the battery compartment on all 5 accessible sides with 20-30mm XPS foam board (the pink or blue rigid insulation from a hardware store). Leave a small air vent for any hydrogen off-gassing. Seal edges with foil tape. This alone buys you 3-5 hours of above-freezing temps after overnight cold.
Will my solar charge the battery in winter?▼
Only if the battery is above 0°C when the sun rises. Insulation or a heating pad ensures the battery is warm enough to accept charge. Otherwise, your MPPT will show available solar power but the BMS blocks it — wasted energy until the battery warms up naturally.