14.4v Rechargable Battery Power Supply ^updated With Banana Terrminals

by busidit

16K388

Intro: 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.

8 Comments

MACKattacksnipe 12 years ago

now all you need is another battery recharger to juice the battery back up

busidit 12 years ago

Indeed. Because I get a charger with every tool I have an excess of chargers. And by the number of lone chargers I see at pawn shops, so do most cordless tool users.
Thanks for looking and for your comment.

jimmykat 13 years ago

hello, I have 2 dewalt and 1 black & decker chargers known as superchargers. They were able to charge differt brands of batteries. I think there was some leagal dispute over it and quit making them early. They had different contacts in the slot the batteries went in. I used a old dead dewalt battery and connected wires to the nose of of old battery and am able to charge many different size battery packs . It automaticaly switches to trickle charge or fast charge. I wish someone could disect one and figure out how it works. If you are able to come across one buy it because it can charge alot of different sizes and brands of batteries

busidit 13 years ago

i don't know enough about different charging cycles on batteries. do you know if the output voltage and current of the charger changes during the cycle or is it constant? i think some or maybe all niCad chargers have a feedback circuit that monitors the current from the battery to let the charger know when to stop. the dewalt charger says it works for batteries 7.2 to 14.4 volts so the charger would need to measure each battery's capacity. i need to read up on this and proceed with caution.
thanks for your comment.

richms 13 years ago

I would chuck a lighter socket on the case as well, handy for plugging in all sorts of car chargers etc for phones and GPS and stuff.

A fuse and a switch would be worthwhile additions to the thing too.

When I wanted to open my charger to see what had gone bang in it, I used a set of reverse drills that got the screws out nice and easy. Stupid "tamper proof" stuff.

kill-a-watt 13 years ago

Ah, had to read it twice, "take an old broken battery charger, strip the guts, and make a holder for a rechargeable battery to power projects". Clever.

I thought at first this was "pull out the leads of this battery charger, and use it to charge other brands of batteries". One of DeWalt's chargers (at least one of them) will auto-sense the voltage and switch to the right program to charge a wide range of battery pack voltages. You could bring out the leads and charge other brands of batteries, if the thermistor is the same across packs (that's the third terminal, and no, I don't know if there's a standard among different brands)

busidit 13 years ago

That would be great to make a universal charger. I'm thinking about adding a pair of terminal blocks to make the outputs more versatile. The gator clips are handy but I would like have other options.

Thanks for your comment.