getting started battery building
Getting Started: Build Your Battery Pack
Choose the right S/P configuration, BMS, nickel, and connectors for power tools, e-bikes/scooters, and DIY projects.
1) Understand S (Series) and P (Parallel)
• Series (S) sets pack voltage. More S → higher voltage.
• Parallel (P) sets capacity (Ah/Wh) and current capability.
| Common S | Nominal Voltage* | Typical Use |
|---|---|---|
| 3S | ~10.8–11.1V | Small portable packs, RC, LED |
| 4S | ~14.4–14.8V | Light tools, robotics |
| 5S | ~18.0–18.5V | Many 18V power tools |
| 6S | ~21.6–22.2V | Higher-power tools, some scooters |
| 10S | ~36V | Common e-bikes / scooters |
| 13S | ~48V | E-bikes, higher-speed scooters |
*Nominal voltage depends on cell chemistry; check your device requirements.
2) Pick Your Cells
- Capacity (Ah) vs Current (A): Power tools favor high-drain cells; e-bikes balance capacity & current.
- Look at continuous discharge rating (A) and internal resistance (IR).
- Shop Cells & Materials — Samsung, Molicel, and more.
3) Size Your Parallel Groups (P)
Estimate your required pack current and capacity:
Pack current capability ≈ cell continuous A × P
Pack capacity (Ah) ≈ cell Ah × P
Pack energy (Wh) ≈ pack nominal V × Ah
Example: If your tool can draw ~40A and your chosen cell is rated 20A continuous, pick at least 2P (20A×2 = 40A). Add margin for heat and longevity (e.g., 3P).
4) Choose a BMS
- Match BMS to your S count and pick a continuous current rating above your expected draw.
- Prefer balanced BMS for multi-S packs.
- Shop BMS & Protection
5) Nickel, Busbars & Wiring
- Use pure nickel (not plated) sized for your current path. Thicker/wider for higher current.
- Keep series paths robust; minimize long, thin traces that bottleneck current.
- Choose connectors rated above expected current (XT30/XT60, JST-XH for balance). Shop connectors & wiring.
- Shop nickel strips
6) Cases & Fit
Choose a case that matches your device and planned S/P layout. Verify space for BMS, wiring, and insulation.
7) Tools You’ll Need
- Spot welder (for nickel), soldering iron (for leads/connectors), heat gun (shrink).
- Multimeter and IR tester (cell matching), insulation (fish-paper, Kapton).
- Shop tools & testers
Safety Essentials
- Wear PPE; prevent shorts with fish-paper rings & Kapton; verify polarity before every weld/solder.
- Use a BMS matched to S count and current; never bypass protection in finished packs.
- Charge with compatible chargers; follow local rules for shipping/transport of lithium.
