Introduction: 14.4v Rechargable Battery Power Supply ^updated With Banana Terrminals
The goal of this Instructable is to make it convenient to use my supply of 14.4 volt rechargeable batteries in prototyping projects.
This is a very simple but useful adaptation of the charger that strips away all the components except those which hold the battery and connect to it two (pos & neg) terminals. It's nothing more than a socket for the battery with easily accessible output leads.
For my outputs I chose to use a two foot length of paired wires with insulated alligator clips at the end. In hindsight, some type of plug or jack mounted on the case would provide even more flexibility. With most of the components removed from the circuit board there is plenty of space for adding new components.
I have a drill and a circular trim saw, each with a few batteries and charger. I really only need one charger in my life so the second one became the doner for this project. I still have an intact charger to keep all the batteries charged.
Step 1: Opening the Case
This particular model has a two-part case secured with 'triangle' head screws that are hidden under plastic foot pads on each corner. The foot pads can be I opted for drilling out he heads rather than buying or making an appropriate screw driver.
Should you need to drill out the screws, a 3/16 inch drill will do.
Don't forget the fifth screw located down inside battery socket.
Step 2: Inside the Case
Once all the screws have been removed the top case should lift off freely. There are no electronic parts or wiring attached to the top case. The AC cord coming into the case routs through a serpentine channel in the bottom case to provide a cord strain-relief.
This is a good opportunity to check out all the components that make it a charger.
Step 3: Removing Parts From the Board
It's harvest time.
Using a soldering iron and a solder sucker, remove all unused components from the board. The only things we really need to keep are the battery terminals, located in the centre.
Although I haven't incorporated the led into the circuit I left it on the board for future connection.
Step 4: Connect New Output Leads
Depending on the gauge of wire used, existing holes in the board can be used to feed the stripped end down to the underside of the battery terminals.
I found it helpful to tin the wires before running the ends through the holes.
When the soldering is complete set the board back into the bottom case in order to avoid strain on the newly soldered connections.
Test fit the case top and adjust wire location as necessary to avoid interference .
Step 5: Close the Case
Replace the top of the case and fasten with new screws in the original locations. I used some #6 x 3/4" long flat-head sheet metal screws.
Note that the the leads will be live as soon as you insert a battery. Be cautious not to leave the leads touching each other on your bench when you put the battery in.
Step 6: Banana Plug Modification
I decided to cut off the alligator leads and connect the leads inside the enclosure to a set of banana plug terminals. These are the type that allow you to plug in any standard male banana plug as well as a bare wire under a thumb-screw terminal. These are great for quick prototyping and switching the power supply between a variety of projects.
I used a stepped bit to drill holes in the front of the enclosure. It worked great and made very clean holes at 5/16 inch diameter for the banana plug terminals.
Inside the enclosure, the wires (cut short from the alligator leads) were soldered to the back of each terminal.
I picked up the terminals from Fry's Electronics.
Spark Fun also carries them:
Part numbers are: PRT 09739 (for the red) and PRT 09740 (for the black)
Radioshack as well as other home audio or home theater shop should carry these in their speaker wiring areas.