Hi, everyone!

Today I'm gonna show you how I converted (replaced) my old Ni-Cd drill to li-ion using 18650.

Step 1: Parts

1) High-Amps (30A) Lithium batteries 18650, capacity 3000mAh (really, tested):

http://s.click.aliexpress.com/e/vue25J6

2) BMS Protection Board For Li-ion (12,6V/3S 20A):

http://s.click.aliexpress.com/e/cGBDG0Gu

3) 12,6V Lithium battery charger (adapter):

http://s.click.aliexpress.com/e/bzHMCzuy

4) Battery level indicator:

http://s.click.aliexpress.com/e/cF8fTkc

5) Small push switch:

http://s.click.aliexpress.com/e/cr67D6dK

6) Some copper wires

Step 2: Disassemble a Drill

1) Disassemble a drill battery handle.

2) Separate contact block from old batteries ("+" on the top and "-" at the side).

3) Break off extra plastic elements.

Step 3: Fitting

4) Find place for all components. I used hot glue gun to make battery pack.

5) I also glued BMS to batteries.

Step 4: Soldering

6) I soldered batteries and BMS protection board together, like shows in the picture. Batteries can not be overheated! So I used soldering acid. I touched it no longer than 1 second. I used 2.5 mm² copper wire.

Theory:

-Electric current. For drills or screw drive we should use high current batteries. I used 30A lithium.

-Voltage. My old batteries are rated at 12V. Every li-ion battery 18650 has 3-4.2V. And so I decided to connect 3 pieces in series. My battery pack has 3*3=9V (discharged) and 4.2*3=12.6V (charged).

-Capucity. My old Ni-Cd batteries had 1200 mAh. My new li-ion batteries has 3000 mAh. I tested it using my tester. So expect more than twice the run time than the original pack.

-BMS. Li-ion batteries must have protection. Batteries can be broken without protection. Short circuit may heat and make fire. For 3 battery in series exist special "3s BMS Protection Boards". Protection board watch for voltage of each battery. It turns off if one of battery has less then about 3V (2.75V maybe). It rated at 25A.

Step 5: Level Indicator

7) I soldered level indicator and button to BMS like in the photo. Don't confuse polarity! And then I covered up battery contacts using insulating tape.

There is special level indicator for 3 batteries 18650. It works from 9 to 12.6V.

8) I soldered contact group to BMS with 2 copper wires 4 mm².

Step 6: Inside Handle

9) Put it inside handle.

I guess I'm lucky :)
My battery handle fit perfectly! Batteries fit tightly, and there is place for indicator. It fit tightly too. I only drilled the hole and poured epoxy into it. I also drilled hole for button.

I'm so happy :D

Battery handle is ready!

Step 7: Charger

10) I disassembled my old charger. I removed all components between input connector and contact plates, and soldered piece of wire to unite input connector to contact plates.

Old adapter can't be used!

Theory: There is special charger for Lithium batteries. For my "3s battery pack" I use 12.6V charger. I chose 1A charger. So charge process takes 3000mAh/1000mA = 3 hours. You may buy 2A, and it will take 3000mAh/2000mA=1,5 hours.

I'm lucky again :) The new charger has plug-in connector like my old! Perfect!