BC-611   B+   Battery Box                bat rev 10-13
      NOTE: See the home index for information on the filament battery setup.
   Overview: The U shaped battery box holds 10 batteries and is fabricated from one piece of sheet aluminum, the ends are fashioned from standard oak stock with a brass bolt on the Plus end and a copper strip on the minus end. The nine volt batteries are wired in series, Plus end to the bolt, minus to the copper strip on the end of the holder. An in-line fuse is used for circuit protection.The batteries make a tight fit in the box, no battery clamps or holders are necessary.
Caution: I have experienced several instances where 9 volt batteries have developed internal leakage and short to the 9 volt batteries metal case. This in turn shorts out to the metal U shaped battery box described on this page. This in turns shorts out the pack draining it and creating heat. Always remove the battery pack when not in use. Do not store your BC-611 with the battery pack inside.
    The completed box shown sitting on top of one of Robert W. Down's excellent reprints of the BC-611 TM.
   Don't like the prices of 9 volt batteries? I buy my 9 volt batteries at the "Dollar Store", my most recent purchase had 2002 date codes so they last for a couple of hamfests then I chuck em. . . but I always cover the terminals with black tape prior to disposing, they have been know to start fires in trash baskets.

   The .025 sheet aluminum is available from your home improvement center. If you do a lot of sheet metal work angle snips are easier to use than straight ones, shown is an angle version..

 

     

 





    A sheet metal brake is handy.

 

 

    Make your first bend and then scribe a line for the second bend.

  




          If you do not have a standard brake then use two pieces of angle aluminum held in a vise.
   



     Or use two pieces of hardwood.
   Put your batteries in your tray and trial fit the U shaped tray before making the oak end pieces.You will have a tight fit but the tray must be able to move in the radio as the door is closed in order to make contact with the base spring at the bottom of the radio.
   The end blocks are approximately 1-1/4 wide and are made out of 1/2 inch oak stock.Spend that extra dollar and obtain oak and the project will be very rugged. The end block sizes will vary slightly depending on your bending of the aluminum box to hold the batteries.




    Counter sink the inside of the Plus end piece to make it easier to solder the positive wire.
   The end blocks are held in place by #4 flat head screws 1/2 long. Obviously if they are any longer they may short out the brass bolt used for the Plus connection.
   


     Counter sink the aluminum for the flat head screws. This is necessary in order to allow the tray to slide in and out of the radio.

   The positive wire is soldered to the cut off  BRASS bolt.  Cut off the bolt after you are sure of a solid contact at both ends of the tray. I know its not red, I  ran out of red teflon wire.

   You can always lengthen the PLUS bolt by adding washers. If you all ready cut off the first bolt and it is now too short then put in a new bolt etc.
   The Plus end of the holder is marked.
   Form a piece of  3/4  wide copper around the bottom of the MINUS block or ground connection. It is fitted around the bottom of the oak block and does not have to be insulated from the bottom of aluminum box. The wide copper strap on the Minus portion of the battery holder is necessary in order to assure good contact with the base spring located in the bottom of the radio. This copper strap is the minus connection for your pack and also makes the case of your home brew pack negative.

        CHANGE: DO NOT GROUND THE COPPER STRAP TO THE ALUMINUM CASE DUE TO PROBLEMS FOUND IN THE 9 VOLT BATTERIES. Some of the 9 volt batteries including brand names have developed shorts from one of the battery terminals to the battery case. The case then comes in contact with the aluminum battery box and developes a short condition.
   

    The copper strap is held in place by a #4 screw on both sides of the end block. Obviously you have to "stagger" the screws are they will collide.
   

    The end of the string of the 9 volt batteries is soldered to the Minus end copper strap on the inside of the block..
            WARNING: No one likes to get shocked. Remember that the aluminum tray will be at ground potential and that by holding the tray and contacting the brass bolt you will be exposed to 90 volts. Don't do the standard battery "tongue test".
   Their are many styles of 9 volt battery connectors , I prefer the more rugged type, buy em at the hamfest or its Rad Shack part number 270-324, very nice rugged connector.
   By twisting the wires as shown and apply heat shrink you will have a good "strain relief" system.
   Hot air shrinks the heat shrink, much better than a match.


               Borrow your wife's hair dryer.
    This type of fuse holder grabs the end of the fuse instead of just touching the end. The holder case was discarded. Heat shrink covered the connections for insulation and strain relief.
   Insulated tubing for housing the fuse holder.You can always check the status of the fuse as the tubing is clear.
    


   A finishing touch is a small lanyard to pull the box out of the radio for service. The servicing lanyard is located near the PLUS end.



   Ready for the 3885 net at the Hamfest.


     Heres a shot of Jerry's K9HXA version of the box

                                            RETURN

                                Link to the filament battery pack page