YOUR ENERGY PROFILE.
This document contains the sizing of your future electrical installation, calculated based on your appliances.
Inventory:
Battery
To guarantee 0WH without damaging your bank (80% max discharge):
Solar
Minimum power required to recharge your consumption:
220V AC
Maximum power (with 25% safety margin).
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
BOÎTE À FUSIBLES 12V
Pompe, Leds, Frigo...
CONVERTISSEUR 220V
NON REQUI
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
Comparison table
| Issue | Symptom | Fix |
|---|---|---|
| Undersized wiring | Shuts off under load, wiring gets warm | Upgrade to 4/0 AWG, shorten runs |
| BMS cutoff too high | Cuts at 50-60% SoC | Adjust via app or contact manufacturer |
| Inverter surge | Shuts off when compressor starts | Add soft-start device, check inrush specs |
| Cold temps | Early shutdown in winter | Self-heating battery or battery blanket |
About this tool
A LiFePO4 battery shutting down early is one of the most frustrating van life experiences — your system was supposedly full charged at sunset, and by midnight the fridge alarms. Understanding why this happens, and how to fix it, starts with identifying which BMS protection triggered.
The main BMS protection mechanisms in a standard LiFePO4: low-voltage cutoff (any cell below 2.5V), over-current cutoff (discharge current exceeds BMS C-rate), over-temperature cutoff (cells above 60°C), under-temperature charge cutoff (temperature below 0°C), and cell imbalance protection (difference between cells exceeds threshold).
Diagnosis checklist: First, when does the shutdown happen? Under high load (inverter running) = overcurrent issue. At night with just the fridge = low voltage from undersized battery or high overnight consumption. In cold weather = temperature cutoff from cheap BMS. Second, what voltage does your Bluetooth battery app show at the moment of cutoff? Above 11.5V suggests overcurrent, not low voltage. Below 11.0V = genuinely depleted.
The most common real-world cause: cell imbalance in budget LiFePO4 packs. When one cell group is weaker than others, it hits the 2.5V minimum while the rest of the pack still has 30% capacity. The BMS correctly protects the weak cell by shutting the whole pack down — but the result is a pack that appears to have 70% remaining capacity while already being "empty." Fix: run the pack through 3-5 full charge-discharge cycles to allow the BMS balancer to equalize cells.
For legitimate capacity shortfall (not a fault, just undersized system): use VanPowerCalc battery calculator to verify. Input your actual overnight loads — fridge cycling at 40W average × 10 hours = 400Wh. LED lights 20W × 3h = 60Wh. Phone charging 15Wh. Diesel heater 8W × 8h = 64Wh. Total: 539Wh overnight. A 100Ah LiFePO4 (1200Wh usable) has comfortable 2.2× margin — but a 75Ah budget pack (900Wh usable) at 60% state when it gets cold in October is going to die at 3 AM every time.
Diagnosing the root cause systematically: First, verify with a multimeter that the battery BMS is actually the cutoff point. Measure voltage at the battery terminals during load — if it drops below 10.5V momentarily, the BMS is doing its job protecting over-discharged cells. Next, measure at the MPPT output terminals: if there is solar available, is the battery accepting charge? A non-accepting battery indicates temperature lockout (BMS blocking charge below 0-5°C) or cell imbalance.
Cell imbalance as the primary cause of premature shutdowns: In multi-cell LiFePO4 packs, one weaker cell hits low-voltage cutoff before the others. The BMS shuts down the entire pack to protect the weak cell, even though 3 of 4 cells (for a 4S pack) still have charge remaining. Fix: a passive or active balancer running during the float/maintenance phase will equalize the cells. Victron MPPT with absorption phase enabled (14.2-14.4V bulk, 30 minutes absorption) provides some passive balancing for most LiFePO4 packs.
Long-term fix for chronically imbalanced packs: manually top-balance cells. Disconnect the BMS, charge each cell individually to exactly 3.65V, reconnect. This is a once-every-2-year maintenance task that keeps packs performing at their rated capacity for the full cycle life.