Make a Battery Substitute Power Connector

Intro: Make a Battery Substitute Power Connector

After the batteries went dead in the middle of a shot using my new camera with double the number of megapixels and features, I discovered there was no external power connector. Once a shot is lost, it may be lost forever, so an external source of power can be a critical option.

This Instructable will show you how to work around a proprietary or a non-existent power connector by making a battery substitute power connector that will allow an external power source to be used.

STEP 1: The Power Supply

Combine or Not?

In many devices, such as a flashlight, the batteries are wired in series. In these devices you may be able to combine the voltages with a single battery substitute connector and power supply that provides only the total voltage, hence one AA = 1.5 votls, so 2 x AA = 3 volts..

In other, more sophisticated devices like cameras the batteries may be wired, or look like they are wired, in series but the series connection between them may be tapped or non-existent. If you are making a battery substitute power connector for one of these devices then you might have to make separate 1.5 volt battery substitute connectors and supplies for each battery the device will use.

External Power Sources

A portable external power supply can be made using a bank of external cells wired in parallel to keep your device going all day.

If you don't need portability as with studio type work a wall wort type power adapter with a minimum rating of 1 amp can be made using a transformer, bridge rectifier and a voltage regulator. Most regulators will handle a supply of up to 36 volts so a wide range of transformers can be used. A large micro farad capacitor with various other circuit refinements can be incorporated to provide power that is smooth. A circuit diagram based on the 78xx voltage regulator series is shown below.

The other options are to purchase a used 1.5 or 3 volts power adapter at a thrift store or a new one from Radio Shack or Wal-Mart for a little more cash. Multiple output voltage adapters, if they have a 1.5 or a 3 volt output, can be used as well but may be more expensive. Be sure you have one that is rated for at least 1 amp output. Otherwise your device will probably not operate or will at some point do the very thing you are trying to over come, which is to shutdown.

I opted for a wall wort type power supply from Radio Shack because one was sitting in my drawer. (Its only rated at .3 amps so I replaced it with a bigger one.)

STEP 2: The Connector

If the adapter has long leads then they may be all that is needed when the plug is removed.Otherwise a 22 AWG or lower AWG set of leads should be acquired. Speaker wire works very well for this application.

A wood dowel with a 13mm to 14mm (1/2") diameter is needed and also several thumbtacks.

I found both the dowel (USP code: 041426027356) and brass thumbtacks (USP code: 027755015240) at Wal-Mart.

STEP 3: The "contacks"

To make the "contacks" simply strip the end of the lead, wind it around the tack and solder.

You'll need at least two "contacks," one for the negative and one for the positive terminal.

STEP 4: Add the "contacks" to the Connector

If you have a device where there may not be a series connection between the batteries then you'll need to cut each piece of dowel to the length of an AA battery minus the height of the thumbtack caps. My thumbtack caps are about 1.5mm.

An AA battery is about 50mm long so the pieces of dowel are cut to 47mm for individual battery substitution and to 97mm for an combined inline configuration. You can adjust this measurement for a tighter or looser fit. In practice 48mm and 98mm gives a little bit tighter fit.

Use a stick pin to start a hole in the center of each end of the dowel. After the holes are started place the point of the thumbtack in the hole and hammer the tack down until it is seated. Mark the end of the dowel with the correct polarity of the "contack."

Tape can be used to secure the wire to the dowel. You can get fancy and cut a channel for the leads along the length of the dowel if battery compartment space is at a premium.

STEP 5: Remote Battery Packs

Shown is just one AA battery but if you cut the piece of inner tube wider you can parallel several batteries for more amperage and amp-hours.

(Hint: Use larger tubes or rubber bands for C and D cells)

STEP 6: Test and Finish Up

Test the contacts with a voltmeter to be sure the polarity and voltage are correct and then test the fit of the connectors and the external power supply in an expendable device.

If there are no voltage anomalies and everything is working then cut a notch in the battery compartment cover in a place where the cover can be closed large enough for the leads to come through.

If everything is still working with the cover closed then you are good to go.

Comments

[snoop911]

Do you know of anywhere online to buy AAA wooden dowels*, i.e. smaller than the AA (13.5mm 1/2")?

Also the battery compartment more tube-like, so I'm thinking the diameter has to be a bit smaller to allow the wire to run alongside, no?

Would a nail fit better than a tack or will that not conduct?

*The places I've seen (batteryeliminatorstore, Blue Planet Electron Corp, 8ten1944, etc), don't seem to carry AAA or thry won't fit in a tube configuration

[smujmaiku]

You can use 3/8" dowels from your local home center for AAA batteries. I just took my measurements of the batteries I was trying to make on my way out at the checkout.

[marcelw123]

hey Danny, I just recently ordered an adapter from batsub.com site that was recommended below. It works great! My wife uses it for our baby’s crib mobile and she said it was pretty easy to set up.

[dannyamz1]

Can you do one for me, or where can I buy one. I need get rid of those two AAA batteries of my keyboard. I find this idea excellent. Great!!

[riverboat]

This is great. I needed to make the AA battery accessible from my battery operated clock so I didn't have to take off the clock face to change the battery. Now the battery is located in a holder outside the clock movement. The dowel and thumb tack approach is just what I needed for the old battery connector.

[BatSub]

Check out the new device at www.batsub.com; It's an adapter that'll help you with battery substituting. I think it's a step in the right direction.

[ortho]

yes dowel is what i used

[andreq]

I've done the exact same thing some years ago to power my (now sold...) Sony MD player. I was eating so much power when transfering music to md that I've created a AA cell just like you did here... 1wood dowel with thumbtacks Nice instructable

[thinkahead]

Thanks. It was a kind of fun project knowing I could beat the man. :-) The need to prevent a shutdown in the middle of a shot, even with less power hungry chips offered in newer cameras, by using an external power pack is just too critical to pass up.

[klee27x]

You might be surprised with the newer cameras. I was extremely upset when I saw how small the battery is for my newest camera. But I have completely loaded and downloaded the memory once or even twice over without even losing a bar. I only put it on the charger after it gets a good workout and is down at least a bar or two... and that's not often.

[thinkahead]

It's mainly other devices without a power connector that inspired this Instructable. For 9 volts batteries I've always just snapped on a 9 volt connector wired to an external power supply. With AA or AAA you can insert a piece of double sided circuit board between the battery and the battery terminal instead of using thumbtacks and a piece of dowel but I wanted to be able to put my discharged batteries into the charger and still be able to use the camera. The newer cameras almost make throwing the older cameras away a no brainer.

[klee27x]

My method would be to glue a 3 pin section of female pin header onto the outside of the camera, next to the battery holder. Then solder 30 AWG kynar wire directly to the battery terminals, connecting them to the port (middle pin positive, outer pins negative). This would create a nonproprietary power plug. Then use clear packing tape to hold the wires down to the battery case. It sounds hard, but it's probably easier than making fake AA batteries. I've done this many times. BTW, you only have to solder two wires, not four. Rarely, some test equipment might run from a +- 1.5V supply, but your typical device only uses the 3 volts in series; two of the leads in that battery clip are actually higly likely to be connected to each other (and to nothing else) and can be ignored, altogether. Actually, the way you wired it, you should be careful to not hook them up to the same 1.5V power source, as you will probably just short the power supply. If the camera has an easy to open plastic case, as yours appears to have, you can even solder your wires directly to the pcb. Then you could either make a tiny hole through which to route the wires, or you may even find enough space to cut a slot for the port's face and mount the entire port internally. Nice instructable!

[garrettmikesmith]

"contacks" - i like it. make sure you have the right amperage though. portable devices pull power out of batteries and wall wart transformers at whatever rate the device needs. batteries supply the device with pretty much any amount of amps needed, because they are drawn out of the batteries. in a wall wart transformer, this is not always the case. if the listed amperage is too high, that's fine, the device will only pull what it needs from the wall unit. if the listed amperage on the wall wart is too low, it will not have sufficient power and could lead to device malfunction.

[thinkahead]

Thanks for the tip! Device load is a very important consideration. I am glad you brought it up. Digital cameras are one of the heaviest loads a battery or a wall wort can have and one of the reasons so much effort has been put into making chips that have low power consumption. An Energizer lithium AA cell is rated at 2 amps continuous and 3 amps pulsed (2 sec on, 8 sec off). That's 3 watts continuous and 4.5 watts pulsed. Most alkalines are rated at 1 amp or less which would be 1.5 watts. If the load is too great for the power supply then the power supply will heat up and so will its leads, if they match the power supply's capacity. Low current is usually not a problem for the device since it is treated like a battery going dead. Too much of a load will cause the voltage to drop which will in turn activate the device's shutdown circuitry. To prevent this a larger regulator or a bigger wall wort up to 3 amps capacity can be used. ...and you are right, a 5 amp regulator would not hurt either.

[garrettmikesmith]

fo sho

[ortho]

I just made one a few weeks ago i was going to post it you beat me to it . what else do ya got?

[thinkahead]

Even if it is exactly the same there is no harm in posting whatever you've got. I have hundreds of things scheduled but to do one right takes a lot of work so I have to be really enthused about it before it gets the go ahead. Do you know how to make a hydrometer? We have been waiting and waiting for someone to do an Instructable on that. :-)

[LinuxH4x0r]

Awesome! I'll have to do this some time

[GorillazMiko]

Intelligent idea. Great pictures, great detail, just great everything. This is truly just a great Instructable. :-)

[thinkahead]

I'm glad you like it. It was kind of fun. In the past I've always just tapped into the battery circuit and added the missing connector myself but in my new camera there is just no room for even the smallest connector to be added.