Battery Adapter for the

PRC-25, PRC-74 and PRC-77 Military Radios

© Brooke Clarke, N6GCE 2004
257477BA Ver 7.2 257477BA-PP
Stock Version
Power Pole Option

Hi Current User Modification
Related Information


The 257477BA is a Battery Adapter that replaces the BA-4386 or BA-5598 in all applications where the CY-2562/PRC-25 battery box is used, such as the PRC-25, PRC-77, PRC-124, PRC-1077, PRC-1099. GRA-114, military radios.  It also works in some applications where another battery box is used such as the PRC-74 with the CY-6314 battery box (but not the "A" version) plus the USQ-42 and USQ-46.  The KY-65, PPS-115, PPS-115A, PRD-10, PRD-12, URR-69, USA-32, URC-100 have not been tested, they might work and might not.

This battery adapter holds 10 each common "D" flashlight batteries.  The batteries can be Alkaline to provide the longest talk time, Ni-Cad or Ni-MH rechargeable for lower life cycle cost. 

There are some plastic battery adapters on the used market that hold 10 "D" cells, but it's done using 3 strings of 3 cells and a lone single cell.  These adapters can NOT be used with the PRC-25 since they can not supply the needed 3 Volts.

This version of the 257477BA is a plug and play solution, no modifications of the radio or battery box are required as was the case with prior versions.

The price includes mailing to U.S. addresses and CA sales tax if you live here.  Made in the U.S.A. by Brooke Clarke, N6GCE.


The 257477BA has the following improvements to the 2577BA.  The 2577BA will still be offered since it has a lower price and works in the PRC-25 and PRC-77.  But the 2577BA requires removing the foam strips from the battery box.

Version 7.2

This version uses a pair of 0.093" thick G10 fiberglass printed circuit boards for the plates instead of the plastic used on the standard 257477BA (Version 6.5).

The fiberglass is much stronger than the plastic used for the prior versions.  Printed circuit traces replace all of the between battery connections.

Load Testing

6 Sep. 2003 -  Using an Electronic Load controlled by a computer a load test was run using 10 each RS 23-519 Ni-MH "D" cells rated at 4.5 AH.  The battery pack lasted 30 hours with a receive load of 0.05 Amps for 9 minutes and a transmit load of 1.1 Amps for 1 minute, repeated until the voltage goes below 10 Volts.  These are the loads from a PRC-25 on the 15 Volt section.  This is about 4.65 AH from batteries rated for 4.5 AH and that have only had a small number of discharge - charge cycles.  11 Sep confirmed that you get 30 hours from 10 each 4.5 AH Ni-MH batteries.

Charging these batteries took 6.64 AH.  It's typical that you need to put more charge into a battery than you take out of it. The efficiency of these batteries is 4.65/6.64 or about 70%.

Note that 9 AH Ni-MH batteries are available and they should last twice as long, or about 60 hours.

Power Pole Option

257477BA-PPThe -PP option adds a pair of Anderson Power Products PP15 "Power Pole" connectors.   The orientation of the Positive and Negative connectors is the one standardized by ARES.   This allows this battery adapter to be used to power equipment that runs on 10 to 15 Volts DC.  For more about vehicle voltages see "What's a 12 Volt battery". 
I recently wanted to power a GPS receiver for 24 hours continously that needed 9 to 32 Volts and it's internal battery would only last 6 hours.  So I soldered a cigarette lighter socket to one the 257477BA V7.2 Battery Adapters.  This worked great.

  The photo on the left is shown with the Positive connector on the left to match the way it shown on the orientation web page. Some Battery options and weights including $/Watt Hour.

257477BA w PPCL cableShowing the 257477BA with the PPCL Cable installed.  You can see that when the PPCL cable is unplugged the 257477BA can be used the same as one without the -PP option.  The Red Cap on the cigarette lighter socket is to keep it clean and to keep keep out coins or other stuff that could cause a short.  Note there is no fuse in the 257477BA.

Power Pole to Cig Lighter cable PPCL

The optional PP-CLS cable has a Power Pole plug on one end and a Cigarette Lighter Socket on the other end.

For those who already have one of my 2577BA or 257477BA battery adapters there are a couple of adapter cables.  Note that the following two cables can be used with my adapter or with an actual battery like a BB-5598, BA-4386, or other PRC-77/PRC-25 battery to get to Power Pole or Cigarette Lighter connections.

25PP Adapter cable
The Optional 25-PP is a short cable with a PRC-25 Battery Plug on one end and a Power Pole connector pair on the other end.  Can be used in any of the PRC-25 type battery adapters and on actual batteries like the BA-5598 or any of the mil batteries that can power a PRC-25 or PRC-77.  Can also be used for charging the battery.  Use the PPCL cable above to get to Cigarette Lighter socket.

Additional Data Sheet for Power Pole Option

Has table showing resistance of complete 257477BA-PP with various types of "D" cells installed.  This allows predicting the putput voltage given the load current.


Operational with the following:

PRC-25, PRC-74 only with the CY-6314 battery box, PRC-77, PSN-6 Loran-C receiver, TS-2963/USQ-46 (the 80718-3 1A3 battery box will only go on one way) so the USQ-42 and USQ-46 should also work.
The PRC-124 = PRC-1088 should work becasue it uses the same battery box.
PRC-1077 reported to work fine.
PRC-1099 uses the CY-2562 so will work.
RT-1185/GRA-114 Receiver-Transmitter uses the  CY-2562 so will work.

Will NOT work with the following:

PRC-74 with the CY-6314A/PRC-74 battery box, KY-38

 Do not know about:

GRC-122, GRQ-26, MSC-25, KY-65, PPS-115, PPS-115A, PPS-15B, PRD-10, PRD-11, PRD-12, URR-69, USA-32,  UGC-74(), DT-561, DT-562, DT-565, MSC-25, R-2116, Tadiran PRC660T, R-2200/GRR-8, URC-100 series radios

Hi Current User Modification

Hi Cur Mod
By warping solder wick (copper braid) around the small end of each spring where it contacts the bottom of the battery and soldering both ends to the wide printed circuit trace the spring resistance is paralleled with the copper braid resistance.  This lowers the total resistance of the pack and is helpful when currents over 1.5 amp are being drawn.  It will not make any noticeable improvement when the adapter is used in a PRC-25 or PRC-77 but will help in radios like the PRC-1099. 

You might be able to pull 4 amps when Ni-MH cells are used instead of about 2 amps for a stock adapter.  Note that although Alkaline cells provide more voltage they are not capable of delivering as high a current as rechargeable cells.  An exception may be the Eveready brand that does have lower internal resistance than other Alkaline cells.

25 Nov 2006 - I have received a report that this mod works well in the PRC-1099 when used in the 20 Watt mode.

Related Information

Vehicle Power Adapter

The VPA2577 can be used to power a PRC-25 or PRC-77 by means of the front panel POWER connector.  The VPA2477 has Power Pole Connectors on one end and so can be powered from the 257477BA-PP.

257477BA Instruction Sheet

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