A 48V e-bike battery is a 13S pack: 13 groups of cells in series, each group made of 3, 4 or 5 cells in parallel. Building one yourself means buying the cells, a spot welder, nickel strip, a BMS, insulation, a connector and the right charger. AliExpress is a very good place for almost all of that, because the factories behind DALY, FNIRSI, Amass and LiitoKala sell there directly. The one exception is the cells themselves, which we explain below. Prices in USD.
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🏆 13 Tools and Parts for a DIY E-Bike Battery
1. Handheld dual-pulse spot welder, battery-powered (for 0.1–0.15 mm nickel)
2. FNIRSI SWM-20 dual-pulse spot welder with screen (pure nickel up to 0.2 mm)
3. Pure N6 nickel strip, 10 m roll (pick 0.15 or 0.2 mm)
5. DALY smart BMS 13S with Bluetooth app and active balancing
6. 18650 cell holders, 100 pcs (snap-together spacers)
7. Self-adhesive insulator rings for the positive terminals, 400 pcs
9. Wide PVC heat-shrink to wrap the finished pack, 5 m
11. 54.6V 2A charger with 3-pin XLR plug, for 48V (13S) packs
12. LiitoKala Lii-M4S 4-slot charger with real capacity test
13. 2-channel 18650/21700 capacity and internal-resistance tester
🔍 Need a different BMS, charger plug or nickel width?
Search OneFindMe in plain words, like "13S BMS 40A common port" or "54.6V charger DC 5.5", and see the current listings in your currency.
Search parts →13S pack sizes at a glance
Capacity depends on the cells you use. The figures below assume genuine 3,000–3,500 mAh 18650 cells. A 13S pack is 48V nominal (46.8V) and 54.6V when full; a 10S pack (36V) charges to 42V.
| Pack | Cells | Capacity | Energy (approx.) | Charger |
|---|---|---|---|---|
| 13S3P (48V) | 39 | 9–10.5 Ah | 420–490 Wh | 54.6V |
| 13S4P (48V) | 52 | 12–14 Ah | 560–655 Wh | 54.6V |
| 13S5P (48V) | 65 | 15–17.5 Ah | 700–820 Wh | 54.6V |
| 10S4P (36V) | 40 | 12–14 Ah | 430–500 Wh | 42V |
Maximum current matters as much as capacity: a group of 3 cells rated 10 A each can deliver about 30 A continuously. Check your motor controller's maximum current and choose cells and a BMS rated above it.
Why the cells are not on this list
Branded 18650 and 21700 cells sold on general marketplaces (Samsung, LG, Molicel, Sony and so on) are very often counterfeit, rewrapped or recycled from old packs, and listings that promise 5,000 mAh or more from an 18650 are simply impossible: real 18650 cells top out at about 3,500–3,600 mAh. For a pack that sits between your legs at 25 km/h, buy cells from a specialist battery retailer that publishes datasheets for each model, and test every cell when it arrives with one of the testers above. Reject any cell that is far below the rest in capacity or above them in internal resistance.
Safety rules
- Never solder directly onto cells: the heat damages them. Spot-weld the nickel instead.
- Use only cells of the same model and batch, at the same voltage (within about 0.05 V) before you connect them.
- Fit the BMS on every pack, and choose one rated above your controller's maximum current. Add a fuse on the main positive lead.
- Put an insulator ring on every positive terminal and barley paper between groups and along the nickel edges, so nothing can chafe through.
- Do the first full charge on a non-flammable surface, awake and nearby. Never charge an untested pack overnight or in a hallway.
- A home-built pack usually voids the bike's warranty and may affect your insurance. If you are not comfortable with any step, a ready-made pack from a local shop is the safer choice.
How to Plan a DIY E-Bike Battery
- Match the voltage to your bike — the controller decides the voltage: a 48V system needs a 13S pack, a 36V system 10S, a 52V system 14S. The label on the old battery or the controller tells you.
- Measure the space first — count how many cells fit the frame bag or case you plan to use. That decides 3P, 4P or 5P more often than the budget does.
- Choose the nickel for the current — for 3P packs, 0.15 mm pure nickel is common; for 4P–5P or high current, use 0.2 mm or two layers. Nickel-plated steel strip heats up under e-bike currents: use pure nickel.
- Pick the welder for the job — a handheld, battery-powered welder is fine for 0.1–0.15 mm nickel and small packs. For 0.2 mm nickel and 39 or more cells, a bench welder like the FNIRSI is faster and more consistent.
- Check the BMS wiring type — common-port BMS boards charge and discharge through the same wires, separate-port boards have two outputs. Follow the wiring diagram on the listing and connect the balance leads in the order shown.
❓ FAQ
Can I build an e-bike battery with parts from AliExpress?
Yes for the tools and parts: spot welders, nickel strip, BMS boards, holders, insulation, connectors and chargers from brands like DALY, FNIRSI, Amass and LiitoKala are sold on AliExpress directly. Buy the cells from a specialist battery retailer and test each one before building.
What is a 13S3P battery?
13 groups in series (13S) of 3 cells in parallel (3P), so 39 cells in total. With 18650 cells it is a 48V pack of about 9–10.5 Ah, depending on the cells.
Which charger do I need for a 48V e-bike battery?
A 54.6V charger, because 13 cells × 4.2V = 54.6V. A 52V (14S) pack needs 58.8V, and a 36V (10S) pack 42V. Also check that the plug matches your battery: XLR, DC 5.5 mm and GX16 are all common.
Which spot welder should I buy?
For small packs and 0.1–0.15 mm nickel, a handheld welder like our first pick is enough. For full e-bike packs with 0.2 mm nickel, the FNIRSI SWM-20 gives steadier welds.
How much do the parts cost?
The picks above range from $3.42 to $47.93 each. A full set of tools and parts for one pack, without the cells, usually costs less than a single ready-made battery. Prices change often by variant.
Can I use 21700 cells instead of 18650?
Yes. 21700 cells hold more energy each, so you need fewer of them, but they need 21700 holders and the pack is slightly thicker. Most of the tools and parts on this list work with both; choose the 21700 variant where a listing offers it.