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.

Shop power tool cases

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.
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