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A single LiFePO4 200Ah runs $400-600 in 2026 and gives you 2560Wh of usable capacity at 95% depth of discharge. Two 100Ah units in parallel cost $500-700 for the same total capacity but add redundancy — if one BMS trips, the other keeps your fridge running. For most builds though? One battery, less wiring, fewer failure points.
Parallel wiring demands equal length, equal gauge cables between both batteries — otherwise one charges faster and its BMS cuts off before the second is full. Real numbers: 50mm² (1/0 AWG) cables for a 2000W inverter drawing 185A at 12V, with a 250A fuse per battery. Use cross-wiring: positive from battery 1, negative from battery 2, to balance internal resistance across the pair.
⚡ Expert tip
Always fuse each battery individually before the common bus bar — not just one main fuse at the output. If an interconnect cable shorts between two unfused batteries, you'll have 400A+ flowing with zero protection. I've seen the aftermath. It's not pretty, and it's completely preventable with two $5 fuses.
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
I started with a single AGM 100Ah — 50Ah usable at 50% DoD, barely enough for a fridge and two lights. Adding a second AGM in parallel gave me 100Ah usable for $350 total, but the pair weighed 120lbs. One LiFePO4 200Ah at $500 gave me 190Ah usable at 55lbs. Easy math. The dual battery argument gets interesting with lithium for two reasons: weight distribution and redundancy. Two 100Ah batteries at 28lbs each are way easier to maneuver into tight spaces than one 55lb unit. I've done installs where the only option was splitting them — one under the bed, one behind the driver seat. But every parallel connection is a potential failure point. A bad crimp on one interconnect cable, and you can have one battery dumping into the other through parasitic resistance. I've seen melted cables from exactly this.
Frequently asked questions
Can you put two different LiFePO4 batteries in parallel?▼
Only if they're the same voltage (12.8V nominal) and same chemistry. Mixing brands is technically possible but risky — different BMS cutoff thresholds mean one disconnects before the other, leaving the second to handle the full load. Same brand, same model, same age. That's the rule.
Is one 200Ah battery better than two 100Ah?▼
For simplicity and cost, yes. A single 200Ah is cheaper ($400-600 vs $500-700 for two 100Ah), has fewer connections, and less that can go wrong. Two 100Ah win on portability (28lbs each vs 55lbs) and redundancy. If space is tight and you need to split the batteries into two locations, dual is the way.
How do you wire two van batteries in parallel safely?▼
Same length cables, same gauge — non-negotiable. Cross-wire: positive from battery 1, negative from battery 2. Fuse each battery's positive terminal individually. Minimum 35mm² (2 AWG) wire for general use, 50mm² (1/0 AWG) if you're running an inverter over 1500W. Keep interconnect cables as short as possible.
How much does a dual battery setup cost?▼
Two LiFePO4 100Ah: $500-700. Add $50-80 for proper interconnect cables (50mm²), lugs, and fuses. A single 200Ah at $400-600 is usually cheaper for the same capacity. The dual setup makes sense when you need the redundancy or can't fit one large battery.
Can you mix AGM and lithium batteries in a van?▼
No. Absolutely not. AGM charges to 14.4V, LiFePO4 to 14.6V — different profiles, different internal resistance, different BMS behavior. The lithium will force-charge the AGM past its limits or the AGM will drag down the lithium. This is a fire hazard. Pick one chemistry and stick with it.