16.8V screwdriver drill battery pack

Building a 16.8V screwdriver drill pack (4 cells in series): lay out the cells to match the BMS, spot-weld + and − with an AWithZ H2, trim and tin the nickel strip, fish-paper insulation, solder the BMS and the two bottom leads, foam, into the case, sticker, test

Jidian Yanjiusuo (Electromechanical Lab) builds a 16.8V screwdriver drill pack. The BMS negative is at the top-left, so the cells are laid out in the BMS’s order; spot-welded with an AWithZ H2 (screen reads 25°C), the excess nickel strip trimmed off, negative and positive welded; the cells are tinned; a small piece of nickel strip is welded on to make soldering the leads easier; fish paper stuck on; the BMS + and − soldered; the two leads at the bottom of the pack soldered; foam stuck on; into the case for a test, a ‘high-power power Li-ion battery, charge once every two months’ sticker applied, test fine, done. Comments ask which welder / how much the welding pen costs, whether the nickel strip is 0.1 and too thin, whether four cells in series is enough capacity; one suggests just welding on a small piece of nickel without tinning.

Outcome

Steps5 steps · click a frame to jump

1. 
   1. Lay out the cells to match the BMS

   16.8V screwdriver drill pack; the BMS negative is at the top-left, so lay out the cells to match the BMS.

   00:00 – 00:11
2. 
   2. AWithZ H2 spot weld, trim excess nickel, weld − and +

   Using the AWithZ H2 spot welder (screen reads 25°C); trim off the excess nickel strip; spot-weld negative and positive.

   00:14 – 00:55
3. 
   3. Tin; weld on a small piece of nickel for easier lead soldering

   Tin the cells (on the nickel strip); cut a small piece of nickel strip and weld it on to make soldering the leads easier.

   00:56 – 01:13
4. 
   4. Fish paper; solder BMS + and −; solder the two bottom leads

   Stick on fish paper; solder the BMS positive and negative; solder the two leads at the bottom of the pack.

   01:22 – 01:44
5. 
   5. Foam, into the case, sticker, test

   Stick on foam; into the case for a test; apply the ‘high-power power Li-ion battery, charge once every two months’ sticker; test fine, done.

   02:06 – 02:23

Bill of materials

Creator’s tips

• Check where the BMS + and − are first, then lay out the cells in the BMS’s order 00:00
• Weld a small extra piece of nickel at the lead points and tin it — makes soldering the leads easier 01:10
• Sticker reminder: charge once every two months 02:13

Li-ion safety