I have an old Racal Airlite powered respirator face shield. The batter pack wouldn't hold a charge for very long. I searched online for a new pack with no luck. They stopped making these a long time ago. But since it still is a good shape and I don't want to spend the $$ for a new model, I decided to rebuild the battery.
On this unit, the battery pack slides inside the top of the face shield. I removed the pack from the helmet. I carefuly removed the plastic cover off the top of the pack to reveal the cells. There where 3 cells inside. They are the same diameter as a standard AA battery but slightly longer. I got my multi meter out and tested the voltage. It read 2.4 volts. I searched online for 3 replacement cells. However, not knowing what they are called and the fact that the cells didn't have any writing on them, I decided to use 2 AA type batteries.
Since I need to charge the new batteries in a standard 1 hour charger, I didn't want to put them into the Racal battery pack. Then I would have to remove them from the pack when I need a charge. So I decided to make my own. I rummaged through my junk for about an hour. I looked through my son's old toys for something that used 2 AA batteries. Finally I found an old plastic flashlight that used 2 AA's.
I took the flashlight apart. I removed the lens and bulb. I ran two wires through the bulb hole in the reflector. I soldered on wire on the two contact points on the back of the reflector, added batteries, and replaced the top of the flashlight. I drilled a hole along the edge of the lens for the wires to stick out. I replaced the lens allowing the wires to pass through using the hole.
I then went back to my junk pile and found a headphone jack and plug (at least that is what I think they are). I soldered the jack to my leads on my flashlight battery pack. The plug I soldered to a 3' length of wire. Then I soldered the other end of this wire to the two connection points on the blower fan on the Racal. I flipped the switch on the flashlight and it fired right up.
I then took an old hacksaw blade and ground the shape teeth off. I bent it in half and made a belt clip similar to one on a tape measure. I put it on the flashlight and made a few more bends so it fit the curve of the light nicely. I added some CA glue and I was off to the shop.
I used it for about 6 hours yesterday and it was still running strong. I'll keep using the batteries until they are completely dead just to get an idea how long they last. I found that the clip works well but I have just been placing the batter pack in the back pocket of my turning smock.
Thanks for looking,