Loading...
Inside. Almost always inside. LiFePO4 cells hate cold — the BMS cuts off charging below 0°C, and outdoor mounting in winter means your battery is useless for half the morning. The only reason to mount outside is severe space constraints.
Indoor mounting keeps the battery at cabin temperature — your diesel heater or body heat keeps it above 5°C through most winter nights. Outdoor (under the van floor) exposes it to ambient temps: at -10°C, the BMS blocks charging until the cells warm up naturally, which can take hours. You lose your entire morning solar window.
⚡ Expert tip
If you absolutely must mount outside (box van with no interior space), build an insulated battery box with a thermostat-controlled heating pad. 20mm XPS foam on all sides + a 50W silicone heater set to activate at 5°C. Total cost: $30-40 in materials. This turns an outdoor mount into a viable year-round solution.
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
The trade-off is space and ventilation. LiFePO4 batteries don't off-gas during normal operation (unlike lead-acid), so ventilation isn't strictly required. But a thermal runaway event — extremely rare but not impossible with a faulty BMS — would release toxic fumes. Most builders compromise: mount inside in a semi-sealed box with a small vent to the outside. This gives you temperature control and safety ventilation. Popular mounting spots: under the rear bench (most common), behind the driver seat, in a custom box under the bed platform. Avoid mounting directly on the metal floor without insulation — the cold floor wicks heat from the battery overnight. A 20mm foam pad underneath makes a real difference.
Frequently asked questions
Is it safe to mount LiFePO4 inside a van?▼
Yes. LiFePO4 is the safest lithium chemistry — no thermal runaway under normal conditions, no off-gassing during regular charge/discharge. A semi-sealed box with a small vent to outside is best practice but more for peace of mind than strict necessity.
Will an outdoor-mounted battery work in winter?▼
Poorly. At -5°C the BMS blocks charging. Your solar and DC-DC charger produce power but the battery can't accept it until cells warm above 0-5°C. In an insulated box with a heating pad, outdoor mounting works year-round. Without insulation, you lose 3-5 hours of charging every cold morning.
Where do most van builders mount the battery?▼
Under the rear bench seat is the most popular spot. It's accessible, out of the way, and stays at cabin temperature. Behind the driver seat and under the bed platform are second and third choices.
Do LiFePO4 batteries need ventilation?▼
Not for normal operation — they don't produce hydrogen like lead-acid. A small vent is recommended as a safety precaution for the extremely unlikely event of a cell failure. A 20mm hole with a louvered cover to outside is plenty.
Can I mount the battery on its side?▼
Most LiFePO4 batteries work in any orientation — there's no liquid electrolyte to leak. Check your specific model's datasheet. Victron, SOK, and BattleBorn all state any-orientation mounting is fine.