This project replaces the original NiCd battery pack of a Black & Decker drill with a custom 3S2P lithium-ion battery pack built from 18650 cells.lls.
The original NiCd battery was mostly dead and no longer held a charge, so instead of buying a replacement pack I designed a new lithium battery that fits inside the original housing.
The pack uses six 18650 cells in a 3S2P configuration, a 40A BMS for protection, and a USB-powered 3S charger module for easy charging.
This drill uses NiCd batteries, which degrade over time. I wanted to keep using this drill and checked out a replacement battery, but it was quite expensive, so I decided to use some of my spare 18650 cells to build a custom pack instead.
Lithium-ion cells offer several advantages:
- Higher energy density
- Lower weight
- No memory effect
- Better voltage stability under load
By building a custom pack using 18650 cells, the drill can continue to be used without purchasing an expensive replacement battery. :yay:
CAD - click to expand
- 3S2P lithium-ion battery configuration
- Six 18650 cells
- Integrated 40A BMS for protection
- USB-C charging
- Compatible with original drill terminals
- Cell Type: 18650 lithium-ion
- Configuration: 3S2P
- Nominal Voltage: 11.1V
- Fully Charged Voltage: 12.6V
- Capacity: depends on the cells used
| Item | Quantity | Description | Example Link |
|---|---|---|---|
| 18650 Li-ion Cells | 6 | 18650 lithium-ion cells | already owned |
| 3S 40A BMS | 1 | Battery Management System for 3S lithium pack providing overcharge, overdischarge, overcurrent protection and balancing | https://es.aliexpress.com/item/1005005676259423.html |
| USB 3S Lithium Charger Module | 1 | USB-powered charger module for charging 3S lithium battery packs | https://es.aliexpress.com/item/1005005856945497.html |
| Nickel Strip | 1 | Nickel strip for spot welding or connecting the 18650 cells together | https://es.aliexpress.com/item/1005011654088021.html |
| Fishpaper | 1 | Insulation material to prevent short circuits between cells and electronics | https://es.aliexpress.com/item/1005006262885255.html |
A 3S 40A BMS is used to provide:
- Overcharge protection
- Overdischarge protection
- Overcurrent protection
Module used:
https://es.aliexpress.com/item/1005005676259423.html
Charging is handled by a USB-powered 3S lithium charger module, which allows the pack to be charged easily from a USB power supply.
Module used:
https://es.aliexpress.com/item/1005005856945497.html
Working with lithium-ion cells requires caution.
Important considerations:
- Use matched cells with similar capacity and internal resistance
- Ensure proper insulation between cells
- Never short-circuit lithium cells
- Use a BMS rated for the current draw of the tool
- Verify correct polarity before connecting the pack
