Panasonic Screw Driver EY503 Battery conversion.

Lithium-ion Safety Concerns:
If you do not know what your are doing or you do not have any experience about these batteries, do not play with them. They can store lot of energy, which can hurt you seriously and you can burn down your home. I have warned you and I won't be responsible for what you are doing. 

Panasonic EY503 is an old excllent screw driver, powered by two Ni-CD or Ni-MH batteries cells size C, supplying tool with 2.4V. I have this tool laying in my drawer unused for decades. I tried to convert it to 3.7 V, to get it used again. 

What you need? 

• Lithium-ion battery, size 18650, 3.7V, 20A or more. 
• some nickel strip to weld onto the battery.
• 15A car fuse. 
• 18650 plus terminal ‘paper’ insulation
• some wire, at least AWG16 for connection (best to use red and black colour).
• Original metal battery contacts (from old battery which need to be converted), one for plus and one for minus terminal.
• some kapton tape. 
• printed battery holder, without any need for print support. 

I do not suggest to solder wire on Lithium-ion battery. If you solder it, there is big risk to damaga battery, which may cause fire!!! I know what I'm talking. It may seemd to be performed sucessfully, but… 

Best solution is to weld nickel strip on the battery. How to do it, you may read here. Some chinese welders could help here. 

The battery is without any BMS. It means: NO protection against short circuit or battery undervoltage. I put a car fuse of 15A as a short circuit protectrion. I use to charge it frequently, especially after extensive use. 

The source of high quality and cheap litium-ion batteries (in EU) could be found here. Choose unprotected and at least 20A or more to be sure. I build several battery packs. One is build with ordinary battery salvaged from a laptop battery. These are low current batteries! As I had it I decided to test. It doesn't matter if the battery will be damaged, because, it hasn't cost me anything. To my surprise it works very well after 3 years of use, but I do not recomment it. 

A great caution need to be taken when you soldering wire in this battery adapter on ‘+’ and ‘-’ terminal, not to make short circuit!!! 

How to open a Panasonic original battery EY9021 for this screw driver, may be found on Youtube. 

When holder with installed battery is finished, put it back in original battery case. Check battery polarity and test it in the screw driver. 

Do not buy cheap lithium-ion batteries on Aliexpress, with any name variation as 'FIRE'! You will be fooled!

The charger for this battery is here.