EverReady #752 ( NEDA 400 )

The EverReady #752 is a big battery supplying 9 volts LT and 90 volts HT. It's most famous application is in Zenith Trans-Oceanic portable tube radios. The battery is too big to be printed onto A4 paper and in order to have joins as inconspicuous as possible it has to be printed in 4 sections.

Just right click your mouse on the required part and select "Print Target" or save to your computer by selecting "Save Target As..." then print it out. Use something like Paint Shop to resize the image so that when completed the battery forms a cuboid with sides 13.875"x4"x2.625" or 354mmx101mmx68mm.  Print onto paper first to check the size then print it onto the thickest card your printer can handle the cut around the each shape. 

The pieces are numbered (1) from Top Left to (4) Bottom Right. There is considerable overlap on 1+2 and 3+4. The scaling should be such that the distance from the edge to the far side of the white circle (the one with the cat in) is 10". Temporarily glue 1 & 2 to a piece of paper with the two haves matched by overlapping. Using a very sharp craft knife and a metal straight edge cut through the overlapping parts to produce a perfect join. Repeat with 3 & 4. Glue 1 to 2 with paper or card reinforcement across the joint. Repeat with 3 & 4. Glue the top and bottom halves together forming a flattened out battery cover. Crease along all bends and form into the completed battery cover. As this battery is so big it will need additional support, thin plywood or corrugated cardboard would be suitable. See here and here for one example made up by Bill Morris.

There is plenty of room inside for 10x9 volt PP3 batteries and 6x1.5 volt "D" cells (the prototype used 3 x 2 "D" cell battery holders) which will fit neatly with the help of a bit of expanded polystyrene padding. If you solder the battery connections on the PP3 batteries then take care as the connections only have point contacts inside and are easily damaged. There is enough room to "daisy chain" the PP3 batteries to save soldering onto the contacts.

Be very careful when handling this battery pack as 90 volts can pack a powerful shock, as I found out. Also if 9 volt alkaline cells are used, due to their low internal resistance shorting the 90 volts together can generate currents of several amps which can generate energies of several hundred watts and is therefore a potential fire hazard. You have been warned!!!!