Building your own LiFePO4 battery from prismatic cells and a separate BMS is a growing trend in the van build community. Here's the realistic picture of cost, complexity, and whether it makes sense for your build.
Why build DIY vs buy assembled?
Cost: Assembled batteries include the cost of a completed BMS, marketing, brand support, and retail markup. With the right cells and a solid BMS, you can build 280Ah for roughly the cost of a quality assembled 100–150Ah battery.
Capacity: Standard assembled batteries come in 50, 100, 200, 300Ah. DIY lets you build exactly 280Ah (4× EVE cells) or 560Ah (8× EVE cells, or 280Ah in 24V) without paying for a non-standard size.
Learning: Understanding what's inside the battery helps you maintain and troubleshoot it.
Common cell choices
EVE 280Ah prismatic cells (~$70–$90/cell from US suppliers; $50–$65/cell from AliExpress with proper vetting):
- 3.2V nominal, 280Ah = 896Wh per cell
- Four cells in series = 12V, 280Ah = 3,360Wh (~$280–$360 in cells alone from US)
- Grade A cells from reputable suppliers match or exceed assembled battery specifications
CATL 200Ah prismatic cells: Higher quality but harder to source; popular in electric vehicle applications; used by some serious van builders.
LiTime/LISHEN 100Ah cells: Some builders buy pre-matched cells from battery suppliers rather than extracting cells from assembled batteries.
Where to source: Docan (US distributor), Amy Wan (AliExpress — order from her specifically, she's vetted in the community), Alibaba with careful vetting. Avoid random AliExpress sellers without community verification — misrepresented capacity is common.
BMS selection
The BMS is the most critical component. For a 280Ah DIY bank:
- JK BMS (Jikong): Most popular in the van DIY community. Active balancer, Bluetooth monitoring, reliable over-current protection. 100A–200A versions for van loads. ~$60–$120.
- Daly BMS: Cheaper, adequate for many builds, but passive balancing only and less refined app. ~$30–$60.
- Victron Smart BMS: Premium option for Victron-ecosystem integration. $150+.
Choose a BMS rated for at least 100A continuous, with active cell balancing for a 280Ah bank. Active balancing prevents capacity drift between cells in a large pack.
Build steps (overview)
- Source cells — verify grade and capacity before buying
- Top-balance cells — charge each cell to 3.65V individually to match state of charge before assembly
- Assemble in series — connect positive of cell 1 to negative of cell 2, etc. (4 cells in series for 12V)
- Install bus bars — compress cells together, install aluminum or copper bus bars between terminals
- Install BMS — connect to cell terminals for monitoring; connect main positive and negative through BMS
- Configure BMS — set cell count, voltage thresholds, current limits via app
- Enclose and secure — wood, aluminum, or plastic enclosure; label terminals clearly
Cost comparison
| Option | Capacity | Cost |
|---|---|---|
| LiTime assembled | 200Ah | ~$480 |
| DIY (4× EVE 280Ah + JK BMS) | 280Ah | ~$340–$440 |
| LiTime assembled | 300Ah | ~$650 |
| DIY (4× EVE 280Ah × 2 parallel) | 560Ah | ~$680–$880 |
The savings are clearest at larger capacities. For a 200Ah build, assembled is often competitive on price when you account for your time.
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