[mikethedruid]

I have begun to work on the 41-81T I snagged on eBay. I started by disassembling the battery. This proved much easier than I had imagined. One end of the cardboard outer case of the battery just opened right up, held in place by two tabs, very neat. Then all the guts including the connector can be removed as a unit. As you can see in the pictures, the connector is in good shape and can be used again.

[Image: https://38.media.tumblr.com/bea722d6809f...1_1280.jpg]

[Image: https://38.media.tumblr.com/215499ce484a...2_1280.jpg]

I counted 41 cells in the B battery section. This means the B voltage was 61.5V. The A seems to have been 4 of the old, large F cells in parallel. Looks like I may be able to use 41 AAA cells in series for the B battery part, and 6 or 8 C cells in parallel for the A supply. I have to do some eyeball and vernier measuring next.

From the looks of the inside of the battery I got this radio just in the nick of time. A few months more and the leakage you see beginning here would have eaten through the cardboard outer covering of the battery and damaged the radio itself. As it is the connector is still fine, and the guts of the battery are intact enough to easily fathom what to make for a substitute.

I wish to keep this battery project thread separate from the actual radio part of the restoration of my 41-81T. That way those whose primary interest is in making a replica battery for one of these can follow my attempt. Those whose main interest is in the radio itself can follow my work there.

[mikethedruid]

To rebuild the guts of the battery I decided to use 41 alkaline AA cells and 6 alkaline D cells. The assembly is pretty straight forward. We will begin with the B battery section. We need to connect the cells in series, so they need to alternate polarity. I used a hot glue gun to attach the batteries to each other.

[Image: https://38.media.tumblr.com/fe4389d64fe2...4_1280.jpg]

Fortunately, I have a straight edge to the base of the shelves on my workbench. This made gluing up the batteries straight and true much easier.

[Image: https://38.media.tumblr.com/f8742d926754...3_1280.jpg]

Now, begin to glue up pairs of batteries going the same direction, and then glue these pairs so that they alternate in direction as shown below, forming the first two rows of the B battery.

[Image: https://38.media.tumblr.com/d98b0c3404cb...2_1280.jpg]

Continue gluing the pairs together until you have 13 pairs, then add the 14th to the top row, reversed from the one before it. Glue on the last row as shown in the following picture, so that one can continue the series connection easily.

[Image: https://38.media.tumblr.com/f4131c70087d...1_1280.jpg]

Next, glue 3 D cells together, all in the same direction as shown below. Make 2 of these.

[Image: https://33.media.tumblr.com/0a6892204c14...0_1280.jpg]

This shows the new inside battery packs in front of the old packs that go inside the A-B battery pack. They are in front of the old packs. Note how much more compact the new B battery section is.

[Image: https://38.media.tumblr.com/3d452deadce2...9_1280.jpg]

Next I wrapped each of these packs with cardboard cut from a cereal box. This helps to isolate and insulate them. It aqlso provides some support to the glued packs because the cardboard is wrapped tightly and hot glued to itself.

[Image: https://38.media.tumblr.com/6026a3ff6e20...8_1280.jpg]

Next wire the B battery so all the cells are in series.

[Image: https://33.media.tumblr.com/502a830e5306...7_1280.jpg]

Wire the A battery packs in parallel.

[Image: https://33.media.tumblr.com/20272ce9c3a5...6_1280.jpg]

I made a tray of thin white cardboard. One could use cereal box cardboard for this too if you have a big enough box. I made it 1/16 inch smaller in each dimension than the inside of the original case so it could slip in easily. Note the cut out on one side for the wires to go through to the connector. The connector can be left on its original cardboard mounting if it is still in good condition like mine was, and the cardboard reused. It will be outside the tray when the final assembly takes place. After soldering the battery sub-packs to the proper terminals of the connector, arrange the packs in the tray as shown here.

[Image: https://38.media.tumblr.com/a5715707f7ef...4_1280.jpg]

Fill the areas all around the packs carefully with pieces of corrugated cardboard so that they are firm, but not so tight as to make the tray bulge. You don't want the finished unit to be too big for the original case.

Below is a picture of the finished guts, with the wires taped in place on top of the padding of corrugated laid atop the B battery pack.

[Image: https://31.media.tumblr.com/e61930444726...3_1280.jpg]

Male a final piece of thin cardboard the exact size as the top of the tray, and tape it in place. then, slip the whole unit back into the original battery case, and you're done.

[Image: https://31.media.tumblr.com/2d4a0f50c542...1_1280.jpg]

[sam]

mike
great job nicely done   
sam

[jerryhawthorne]

Very nice work Mike. Thanks for the step by step.
Jerry

[morzh]

Hate to ask that but will you be soldeing all these every time your battery goes flat?

[jerryhawthorne]

Morzh, your a kill joy! You just don't run the radio 24/7. Should last a long time. The joy is that it really looks original and a nice job of it. Personally on the farm radios I have done I built an A/C powersupply into the battery box but nothing looks less original than a "battery" with an A/C cord coming out of it.
Jerry

[mikethedruid]

I don't intend to run the radio very much, just for demonstration purposes. Now that the cardboard is all cut and ready, all I will have to do is make new battery packs for the inside, and that is relatively easy... just an evenings work; so if I have to do the job every 3 years or so, no big deal. It would be very easy to make a suitable power supply that will fit in the radio also, made to the same dimensions as the original battery, but I would have to make a small cut in the radio's back on one edge for the cord to come out. Right now the back as well as the rest of the case is perfect, and I'd rather leave it like that.

[Mondial]

Mike, you might want to consider placing the complete battery assembly in a plastic bag before inserting into the original Philco battery case. This way, if any of the cells should leak in the future, it will be contained and prevent any damage to the original case or the battery compartment.

I have seen too many alkaline AA and D cells leak unexpectedly to trust them without taking some precautions. 

[mikethedruid]

Like any of my radios... I have many vintage transistor sets too... I won't leave the battery inside. I will display them side by side except to play the radio

[Arran]

 If you don't want leaky batteries, stay away from Energizers, I've seen those spring a leak after a year sometimes, Ray-O-Vacs are fine I think and that store brand I don't know about.
Regards
Arran

[mikethedruid]

I have always liked Ray-O-Vac batteries better than Everready... as far back as the old yellow and blue Ray -O-Vac cells, and the old Everready cells with the cat jumping through the 9 in "9 Lives".

[Raleigh]

Very elegant solution to restore the innards of your battery. I didn't think you should solder to batteries without tabs (don't know why I thought that) so I made mine with 9 volt batteries in series for the B supply. I haven't had to replace mine in many years of light use, so yours ought to last forever with series AAAs.

Odd, but the Philco service package I obtained from Chuck Schwark seems to have contradictory specifications. First it specifies the P-41A-4G battery, which obviously produces a 61.5 volts nominal B supply. But the power specification on the same page specifies a 90 volt B supply.

I originally made my repro battery with 7 nine volt batteries in series to make 63 volts. The radio worked perfectly well. Later, when I'd bought the schematic from Chuck and saw the 90 volt specification I thought that maybe the 90 B supply in the spec would improve something, so I added 3 more 9 Volt batteries in series for 90 volts. Nothing in the radio's performance changed. I didn't make current measurements to see if that changed.

[Raleigh]

One last post. I suddenly realized what the part number of the battery means.

P-41A-4G derives from the 41 "A" cells + 4 "G" cells used in the battery. (You guessed "F" cells, Mike, but I bet they're "G" cells. I'll have to make an attempt to measure them through all that tar and see if I can tell which they are.)

"A" cells were very slightly larger than today's "AA" cells. You can still buy some batteries in "A" size. They'll fit in modern "AA" battery holders, only a slightly tighter squeeze.

"G" cells were a tiny bit longer and a tiny bit bigger diameter than 2 of today's "D" cells put end to end.

I have only one other original Philco battery. I'll have to check out the part number and see if it derives from the cells in the battery. I think I still have the original guts tucked away in my basement.

[mikethedruid]

Raleigh, thanks so much for the information about the B voltage, and your experiment with it, very good information. You must be right about the A cells. I noticed the original cells in the battery were slightly larger than the AA cells I used in my assembly, and hence the final assembly I made was slightly smaller than the original. When soldering to the batteries I paint the area to be soldered with a little liquid rosin flux (violin rosin dissolved in rubbing alcohol) which works great to allow the solder to bond to the cell's top and bottom. This is the second B battery I have made. My first was a 22 1/2 volt B battery I made to use with my Radiola Senior. http://36.media.tumblr.com/29dd66db4c277...1_1280.jpg .

[Raleigh]

That 22 1/2 volt battery is a good looking project, Mike. It looks like you made the box and printed the graphics, too, or is that original cardboard?

I made some measurements this morning on the guts of the P-41A-4G battery. It was difficult to get good measurements with the tar. I was pressed for time, so I didn't do thorough measuring or calculating, but I'm inclined to believe that the A supply in that battery are paralleled "F" cells as you suggested. That means my clever interpretation of the Philco numbering scheme for that battery is wrong.

I haven't looked at the other battery I have, for a 46-350, to see if the internal cells match the part number. I also remembered I have an original Philco battery for a Mystery Control. When I have some time, maybe next week, I'll pull those out and compare the cells with the part number, but I think maybe I jumped to conclusions.

Beautiful work on your battery reproductions.