This is a project that I have wanted to do (and tried to do), for several months now. It has bitten me in the butt many times, but it has never worked out. This time I think it's close enough to post, but it's still a hack job.
I started out wanting to make a 4AA battery holder for Maglites that have been bored out. Well, until I got to the point where I could bore out a Maglite fairly easily, it wasn't really worth doing. I tried a 3AA version a couple times, only to fail and since 3AA holders are readily available, it was easier to just rework them, than to make new ones.
Now that I can bore Maglite bodies, a 4AA holder has become a necessity and since I made my wooden drill press, it's something that is can be done.
This holder is not a 4AA. It is an 8AA (4S/2P) holder, but the basics are the same for 4, 8, or 12AA.
To begin with, I must say that this was a real bear and I do not want to make these except for my own Maglite builds. This thing took the better part of two days and I am still not satisfied with it. I feel if you need a 4AA holder, it is best to wait and buy one from one of the vendors on CPF. Their holders are made well and well worth the bucks.... But, if you want to tackle something like this, here's how I did it.
First of all, you will need a drill press. Without one, don't try it. The holes that have to be bored, have to be precise and you cannot do that with just a drill and will power. I know, I have tried and tried and tried.
Next is the plastic rod stock, to make the end caps out of. I bought 1-3/8" 6/6 Nylon stock from Drillspot. I got it with free shipping. Drillspot is one of the few places offering free shipping on many items. I used Nylon because rods made out of it have tight tolerances. Some of the other plastics have rather large tolerances in diameter and I needed the OD to be very close to the specified 1-3/8".
The rest of the components consisted of 5/32" brass tubing & 5/32" copper tubing,(from a local hobby shop), 1/8"x7/8" aluminum pop rivets (from amazon, I couldn't find them locally in this size), 0.010" copper sheet (from a local hobby shop) and some gold plated springs (from CNQG).
I did not use the rubber grommets shown. The aluminum template I made from aluminum sheet bought at a local hobby shop. (which has just gone out of business because they can't compete with the Chinese hobby kings). I won't have a resource for this stuff any more unless I want to pay higher prices for shipping.
I purchased a CMT brand 15mm Forstner bit online. That is what I used to bore the holes for the batteries. This CMT bit is very high quality and worked well. I just cut off 2- 12mm thick sections off the nylon rod stock and bored the holes with my drill press, using the template. (which is still not perfect, as seen in the photo). One hole is more outboard than the rest.
Then I drilled the 5/32" holes for the brass support rods and the center hole for the copper positive rod.
After that, it's a matter of cutting out the copper contact plates and soldering the springs and copper tube in place.
Since this is a 4S/2P holder, the positive and negative points both end up in the bottom (negative end cap), so I used the center copper tube to bring the positive back up through to the top.
I did not try to cut perfect rounds. I just cut out the pieces in hexagon (straight cuts), shape and sanded the edges to smooth them out a little. It's not rocket science. When I soldered the springs on, I just tinned the whole contact and set the springs on and flowed them in place. Much easier to heat it that way, than to mess with each spring.
The copper and brass rods are a tight fit, but I wanted to make sure the brass rods would not pull out, so I used the pop rivets in the ends, to help keep them in place. Here's some shots of the completed holder. The contact plates are epoxied to the plastic.
Inside the bottom (negative) end.
Outside of the bottom (negative) end.
Inside of the top (positive) end.
Outside of the top (positive) end. I am not sure what I want to do for the positive contact yet, so I left it as is.
Here's the finished holder with eneloops in it. They were charged a week ago.
I read 5.23 volts from my cheap meter.
That's about it. One thing I forgot was the shrink wrap to go over the center tube, but I don't think it's a problem as long as the batteries have good sleeves on them.
This holder is bound for TJ. I only wanted to try one and see if it would work. He can test it out. I'm done with it now. I am still hoping to find a source for 4AA holders. This thing took way too much time and money to make and it isn't anything I really want to use. It's just a homemade hack.
-Justin