PRC-90 Battery Adapters 90BA & 90BAv2

©Brooke Clarke, N6GCE
90BAv2 
Operational
Fig 1
90BAv2
Fig 2
90BAv2
Positive end showing
Cap is Negative
Fig 3
90BAv2
O-Ring is installed on radio
Fig 4

90BAv2 Description

This is a functional replacement for the BA-1568/U Mercury battery (NSN 6135-00-838-0706) used in the PRC-90, PRC-90-1, PRC-90-2, PRC-103, PRC-106, and PRC-125 (but not the PRC-63) survival radios and the training version of these, maybe the PRC-604 radio.  It uses 4 each CR123 type LiMnO2 photo batteries in a cap that extends about 3" below radio.  Has groove to allow attaching to radio earphone strap with 8" tie wrap (included).  The 123 cells are rarted at 1.3 AH compared to the BA-1568/U rating of 1.0 AH. 

When 4 each 123 batteries are tested with the BT-2B the meter reads 0.8 where 0.5 is full scale for the BA-1568/U.  I don't know the capacity of the BA-5368/U LiMnO2 battery (NSN 6135-01-435-7947), but have been told a number of times it is very expensive.

I cut off the old cap, see Fig 1 and 2 above, and used an 8" tie warp to attach the adapter through an eyelet hole in the earphone strap.  This allows room to remove the adapter from the radio to change batteries. 

Installation

  • Lightly coat O-ring with Radio Shack Lube Gel  64-2326 or equivalent Silicon grease.
  • Install O-Ring onto radio past threads as shown in Figure 4 above
  • Place Plastic tube into battery adapter
  • Slide 4 each 123 photo batteries into adapter Negative end first (cap is negative) will look like Fig 3 above
  • Screw on 90BAv2 adapter until it seats on radio
  • Apply sticker to radio with install date and a replace date (maybe 5 years until replacement)
  • Optionally attach tie wrap to groove in adapter and tie to radio earphone pouch strap eyelets.

  • Leave a little slack so that adapter can turn for removing and installing.
  • Optionally cut off old battery cap after confirming good operation.
  • 90BAv1(Test Only)

    This adapter uses 2 each RS 23-266 Lithium 6 volt Batteries (2CR-1/3N) in series.  It is designed for the PRC-90-(), PRC-103 and PRC-106 or other devices that use the BA-1568/U Mercury battery.  The radio cap is the negative terminal, batteries go in positive end first.  The adapter is not designed to replace the BA-1568/U battery, only to allow testing the radio.  Image of 90BAv1 with label.

    It  works with Lithium batteries like:  2 each Energizer L544 or, 2 each Duracell PX28L or, 2 each K28L or, 2 each Radio Shack 23-266 or, 2 each Sanyo 2CR-1/3N or, 2 each NEDA 1406LC or, 2 each IEC 2CR11108 or Alkaline batteries like: 2 each Radio Shack 23-469 or, 2 each Energizer A544 or, 2 each Duracell PX28A or, 2 each NEDA 1414A or, 2 each IEC 4LR44.  The Lithium batteries have better shelf life and capacity but for a higher price.

    Survival Vest Radio Pocket NSN 8415-00-442-3616

    The pocket that can be sewn onto survival vest SRU-21 will hold the PRC-90 with the 90BAv2 battery adapter attached.  My pocket has contract number DLA-100-82C-C-0394 and manufacturer Camlet Corporation,Roch. NY.  If the radio is installed into the vest antenna first then the battery adapter makes a nice handle to remove the radio.

    Tester for Mercury BA-1568/U

    The BT-2B survival radio battery tester shows them to be at the normal 50% indication for a full BA-1568/U.  Note that the modern batteries may have different capacity than the original battery so the test set no longer is calibrated.  I have a couple of old stock (9/88) Mercury batteries, one shows a little below 50% and the other starts at 40% and drifts down to 30% in a matter of seconds.
    The RS 23-266 (2CR-1/3N) is rated 0.16 mAH and the PRC-90 draws 35 mA in receive mode so these might last about 4.5 hours in receive more, much less in transmit mode.  A fresh BA-1568/U might last 14 hours according to the booklet that is attached to the BT-2B test shown in the photo above.

    The LiMn02 photo 123 type batteries have a very flat discharge curve and can NOT be tested in the BT-2B tester.
    When fresh batteries are installed a sticker should be placed on the radio with an installation date and a replace date.  The LiMn02 battery has a 10 year shelf life and I've seen 5 years used as a replacement cycle time.

    Testing Survival Radios

    Since Satellites are monitoring the survival frequencies you do not want to start a search.  The ACR web page has some guidelines on how to test survival radios.

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    Disclaimer

    This adapter was designed for SAR ground work to allow CAP personal to communicate with military aircraft involved in the search.  It has not been tested or certified for any official use.  If used for survival purposes it's at the users own risk.

    Mercury Battery Warning

    The above units originally used Mercury based batteries.  Mercury is one of the heavy metals that has been found to be bad for humans. (Lead wine containers may have caused the end of the Roman empire?)  Any military battery whose model number is BA-1001 to BA-1999 is a Mercury battery.  These should be kept in Zip-Lock bags and disposed of in accordance with hazardous materials regulations.  If any crystals form on the battery they should be considered as poison.
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