Instructions for 257477BA Battery Adapter

© Brooke Clarke 2001 - 2004

Intended Use

This battery adapter is intended to hold 10 each “D” cells for use on the PRC-25, CY-6314/PRC-74 (not the CY-6314A) or PRC-77 radios  It should also fit any application where the battery box is the CY-2562/PRC-25.  It supplies both the 3 Volt “A” source and the +15 Volt “B” source.  Because the height of the adapter exceeds the height of a BA-4386/U battery the 257477BA may not fit in other BA-4386/U applications.

Choosing a Battery Chemistry

This is just a rough guide to selecting battery chemistry:
Alkaline – offers the highest Amp Hour capacity – typically 18 AH and under $13 at Wal-Mart for Energizer E95 cells. Not rechargeable.
NiCad – Rechargeable lowers cost per AH but suffers from “memory”.  The capacity per cell might be the same as a “C” NiCad at around 2 AH (RS 23-123 ) or might be around 4.5 AH Be sure to watch the price per AH.
NMH – the Nickel Metal Hydride chemistry gets rid of the “memory” problem of the NiCad but may have a problem with capacity decreasing after a number of charge – discharge cycles. 4 AH (RS 23-519)
Rayovac 713 Rechargeable – These don’t have as many charge – discharge cycles as the other rechargeable types, have no “memory” problems and are priced like NiCads. 5.8 AH (RS 960-1812 ).

Installing batteries into the 257477BA

Place the 257477BA on a flat surface with the socket on your left facing down.  Lift up and starting with the top left side, install a battery by compressing the spring with your left index finger and inserting the battery so as to further compress the spring and insert the positive battery contact into the snap.  Some “D” cells have a slightly larger positive contact diameter and for those you should use both thumbs to seat the positive contact into the snap. Turn the 257477BA end for end and install a battery in position next to the just installed battery.  Repeat the above process 10 times in a zig-zag patttern.  Check all cells to be sure that the positive contact is seated in its snap and the battery is more or less in line. (Sometimes the spring will be to one side and needs to be more centered).


Testing the 257477BA 

A voltmeter should measure about 3 Volts from the black wire to the socket pin that has the resistor and about 15 Volts from the black wire to the red wire with the 2577BA disconnected from the radio.   This is a check that the cells are installed properly.  It is not a test of the state of charge of the cells. (2.6 Volts & 13 Volts for fresh NiCad & NMH).


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Because the 3 Volt supply is obtained by tapping up 2 cells from ground the lower 2 cells will be more depleted than the others.  It may prolong the battery life if these two were charged separately from the other 8 cells.  Also it would be good to “rotate” which two cells were used for the 3 Volt supply.  With the 257477BA positioned so the socket is to the right and pointing up the top two batteries closest to the socket (the ones on the right side) are supplying the 3 Volts.

Installing the 257477BA into the CY-2562/PRC-25

Set the PRC-25 or PRC-77 radio on a flat surface with the panel down (radio resting on the two handles) with the battery connector pointing up.  Lower the 2577BA onto the radio while holding it about level.  Position the end of the 257477BA that is away from the socket so that the 2577BA is centered along the axis of the radio.  Install the battery box and latch it.  Engage both latches then close them at the same time.

Installing the 257477BA into the CY-6314/PRC-74 Dry battery Box

Remove the CY-6314 Dry Battery Box from the PRC-74 radio.  Disengage the two catches and seperate the battery box cover from the battery holder.  Losen the 4 wing nuts so that there is a gap of greater than 2.5" along the side to provide clearance for the 257477BA (this is about 1" from the end of the threaded rod). Place the 257477BA into the box with the connector toward the fixed part of the battery holder.  If yout try to install the 2577BAv6.5 with it's socket mating to the movable socket on the hold down cover the fixed pins will interfere with one of the "D" cells.

PRC-25 & PRC-77 Function Switch battery Check

Turn the Function switch on the PRC-25 or PRC-77 to the LITE position; the frequency readout dials should be illuminated.  This tests the 3 Volt section on a PRC-25, which is the first section to go dead, and the 15 Volt section on a PRC-77 (which does not use the 3 V section).


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