Been working on putting together a display with my SCR-610 and wanted to add an RM-29 Remote Control hooked up to an EE-8 Field Phone. It would all be much more interesting if the phone hookup all worked correctly. I was held up with the 4-1/2V BA-27 battery for the RM-29.
After some research, I found a few photos of an original BA-27 sold online at some time in the past. Some more digging indicated that the BA-27 was the military version of the standard 4-1/2V portable radio C-circuit battery. There are a lot of these vintage civilian batteries for sale online, and after looking at a bunch and reading the auction descriptions, I was able to determine the standard dimensions (4" x 3" x 1.375").
Working with the photos of the original BA-27, the details and markings could be figured out. After some experimentation and testing, I came up with a pattern for the box and what I feel is a pretty fair copy of the markings. After a few prototypes, I think that I've come up with a pretty good repro battery that I can display and which also works, giving the correct voltage across each of the different terminals.
Here's the original that I was modeling my repro battery on:
Here's one of my repro batteries installed in my RM-29-A Remote Control. It fits well, but I can now understand what might have motivated the revised RM-29-B. The -A has a shelf over the battery compartment and wiggling the battery into the space is a bit of a challenge. The -B unit had a revised internal layout that did away with the shelf, the battery just dropped into the compartment without the shelf getting in the way.
At any rate, the repro battery fits really well once in place. The RM-29 with the repro battery works perfectly in the phone mode and coms between the remote control and an EE-8 Field Phone is clear as a bell.
Once I had the design and construction process figured out, I made two repro BA-27, one for the control unit and another to display.
One thing that I did was make the repro batteries so that I can remove and replace the dry-cell actual batteries. To enable this, I made the bottoms of the repro batteries open and close like a normal cardboard box. (The original appeared to be glued closed all around - use, dispose and replace.)
The repro batteries take 3, standard c-cell 1-1/2V batteries. I wired the c-cell box so that one negative terminal on the repro battery gives 1-1/2V, the second gives 3V and the last negative terminal provides 4-1/2V.
I also coated the repro batteries with paraffin wax to give them the look and feel of the original moisture resistant BA-27.
Don't know if there's might be any interest in these, but if enough folks want one, making a few of them is entirely possible. I see a lot of the RM-29-* Remote Control units for sale online, and for anyone interested in field phones, it works really well with the EE-8 while offering up an interesting accessory to go with a number of different radio sets.
