DIY LiFePO4 Battery for a Campervan: Is It Worth It?

Building your own LiFePO4 battery from cells is a popular route in the campervan community — mainly because it can halve the cost of a ready-made unit. But it comes with real complexity and real risks. Here is an honest look at both sides.

Why people build DIY LiFePO4 batteries

Cost. A ready-made 200Ah 12V LiFePO4 battery from a reputable brand costs £350–800. The same capacity in raw cells (EVE or CATL 280Ah prismatic cells, 4 in series for 12V) costs £180–300 for cells, plus £50–100 for a BMS. Total: £230–400 for a 280Ah bank, more capacity than the ready-made unit at lower cost.

Capacity flexibility. You choose the exact Ah rating — 200Ah, 300Ah, 400Ah — by selecting cell capacity and configuration.

Repairability. If a cell fails, you can replace that cell rather than the whole battery. A BMS failure can also be fixed by replacing the BMS.

Components needed

1. LiFePO4 prismatic cells

• EVE 280Ah: most commonly used in DIY builds, widely available on AliExpress and UK sellers
• CATL 230Ah, 280Ah: also widely used
• Grade A cells from reputable suppliers come with matched capacity ratings

2. BMS (Battery Management System)

• JK BMS 100A or 200A — the most popular choice for quality and features
• Daly BMS — budget option, fewer features
• Overkill Solar — popular in the US, available in UK too
• The BMS must be rated for your expected peak current, not just nominal

3. Bus bars Copper bus bars connect the cells in series. Many cell kits include these. Ensure the contact surfaces are clean and bolts are torqued to spec.

4. Battery case or enclosure A plywood or aluminium enclosure keeps cells compressed (compression is important for prismatic cell longevity) and protects them from damage. Pre-made enclosures are available, or build your own.

5. Fuse and cables Same as any battery: ANL fuse close to the positive terminal, appropriate cable sizing for your expected current.

The build process

1. Top balance cells: Before assembling, charge each cell individually to 3.65V to ensure all cells start at equal voltage. This is critical — a poorly balanced pack performs worse and stresses the BMS from day one.
2. Assemble in series: Connect cells positive-to-negative in sequence. 4 cells × 3.2V = 12.8V nominal.
3. Install BMS: Connect balance wires from each cell junction to the BMS. Connect the main positive and negative through the BMS.
4. Verify: Check pack voltage before connecting anything. Apply load gradually and monitor cell voltages via BMS app.

The risks

No warranty or certification: A DIY battery has no CE marking, no UL certification, no manufacturer warranty. This has insurance implications — if a fire occurs and it's attributed to a DIY battery, insurance may not pay out. Van conversion insurance policies vary on this.

Build quality: A poorly assembled pack (undertorqued bus bars, wrong BMS settings, unbalanced cells) can fail in ways that damage other equipment or cause fire. A ready-made battery from a reputable manufacturer has been tested and validated.

Time investment: Top balancing, assembly, wiring, and testing a pack takes 4–8 hours for an experienced builder. Factor this in against cost savings.

The verdict

DIY LiFePO4 is worth considering if:

• You are comfortable with electronics and can follow detailed build guides
• You want more than 200Ah capacity (where savings become significant)
• You are prepared for the warranty and certification implications

For most first-time van builders, a ready-made battery from Fogstar, Victron, or similar is lower-risk and still much better value than AGM. The DIY route is more appropriate for second builds or for builders who specifically enjoy the technical side.

FAQ

Where do I buy LiFePO4 cells in the UK?

EVE and CATL cells are available from UK suppliers including Fogstar (cells sold separately), Battery Hookup, and various AliExpress sellers. Buying from a UK supplier avoids import duty and provides some recourse if cells are not as advertised.

Is a DIY LiFePO4 battery legal in a campervan?

Building and using a DIY battery is not illegal, but there is no certification body for DIY batteries. Some campervan conversion insurance policies exclude DIY electrical work — check your policy wording.

What BMS should I use for a DIY build?

The JK BMS (active balancing, Bluetooth monitoring, good reputation in the community) is the most recommended BMS for UK DIY builds. Choose a current rating that exceeds your peak load by 20%.