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
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Comparison table
| Feature | AGM | LiFePO4 |
|---|---|---|
| Usable capacity | 50% | 80-95% |
| Cycle life | 400-700 | 3,000-6,000 |
| Weight (200Ah) | 58-65 kg | 18-22 kg |
| Charge time | 8-12h | 1-2h |
| Deep discharge OK | No | Yes |
| Price 100Ah | $80-150 | $250-400 |
About this tool
AGM Battery Size for Van Builds: Complete Sizing Guide
AGM (Absorbent Glass Mat) batteries remain a popular choice for van builds because of lower upfront cost and availability. But correctly sizing an AGM system requires understanding their key limitation: the 50% depth of discharge (DoD) rule.
The Critical 50% DoD Rule for AGM
Unlike LiFePO4 (which handles 80% DoD safely), consistently discharging AGM below 50% causes rapid capacity loss. An AGM discharged to 80% regularly will lose 50% of its capacity within 6-12 months.
Practical implication: Double your Ah requirement when buying AGM.
Calculation: Required AGM Ah = (Daily Wh × Days autonomy) ÷ (12V × 0.50)
Example: 800Wh/day × 2 days = 1,600Wh ÷ 6V = 267Ah AGM for 2 days of safe autonomy.
AGM vs LiFePO4 Side-by-Side
| Factor | AGM 200Ah | LiFePO4 200Ah |
|---|---|---|
| Usable energy | 1,200Wh (50% DoD) | 1,920Wh (80% DoD) |
| Equivalent to | LiFePO4 125Ah | AGM 320Ah |
| Weight | ~55 kg | ~24 kg |
| Cycle life | 300-600 cycles | 3,000-5,000 cycles |
| Cost (pair) | $200-350 | $400-700 |
| 5-year total cost | ~$500+ (replacements) | ~$400-700 (one set) |
Recommended AGM Sizes for Common Van Builds
| Build Type | Daily Consumption | Recommended AGM | Equivalent LiFePO4 |
|---|---|---|---|
| Weekend warrior (2 days) | 400-600Wh | 150-200Ah | 100Ah |
| Weekend moderate | 600-900Wh | 200-300Ah | 150Ah |
| Short trips (3-4 days) | 800Wh | 300-400Ah | 200Ah |
| Full-time: not recommended | 1,000Wh+ | 500Ah+ | 300Ah |
For full-time van life, AGM becomes impractical — the weight, cost of replacement, and lower usable capacity make LiFePO4 the clearly superior long-term choice.
AGM Charging Requirements
AGM batteries require a 3-stage charger (bulk → absorption → float). They do NOT tolerate temperatures below -20°C for charging (risk of damage). Key charging parameters:
- Absorption voltage: 14.4V (12V system)
- Float voltage: 13.5-13.8V
- Max charge current: C/5 recommended (20A for 100Ah battery)
When AGM Makes Sense in a Van Build
AGM is appropriate for: occasional weekend use, tight budget with no expectation of daily use, builds where the weight difference doesn't matter, or as a starter option before upgrading to LiFePO4.
Expert tip: If you're considering 300Ah+ of AGM for full-time use, the maths strongly favor LiFePO4. A 300Ah AGM bank (usable: 1,800Wh) weighs ~90 kg and costs $600-900. Equivalent LiFePO4 200Ah (usable: 1,920Wh) weighs 22-28 kg and costs $400-700 — lighter and often cheaper over 3 years.