A2E Battery Pack

BUILDING AN AA BATTERY POWER PACK FOR THE CANON EOS A2E

Background Information: Unlike with most prosumer camera bodies, no optional power boosters are offered for the Canon EOS A2E (and it's variants, the EOS 5 and A2). Canon offers the VG-10 grip but it provides vertical controls only, without any ability to supply additional power. For those looking to use a less expensive, longer lasting, and more readily available power source than the 2CR5 battery which the A2E normally takes, Canon offers the BP-5 battery pack. The BP-5 consists of a D cell battery pack that clips to your waist and delivers power to the camera via a dummy battery connected by a coiled power cord. I felt this was kludge method of tackling the battery problem so I tried to develop a solution using AA cells integrated into the camera strap. Initial attempts were made to use only 4 AA cells which results in the same voltage (6V when wired in series) as the standard 2CR5 battery. However, it turns out that if you use this setup with alkaline batteries, the camera's battery meter will read near empty even with fresh alkaline batteries. Apparently the high internal resistance of alkalines affect the meter reading so 2 serial battery strings (with 4 AA batteries in each string) were wired in parallel to boost the current capacity. Using 8 fresh alkalines in this configuration, the meter reads full and the battery life is extended by approximately 100% (to ~25rolls) per set of 8 batteries. The following tutorial outlines the steps necessary in creating this power pack. There are however, definite drawbacks that should be noted:

The bulk of the batteries sometimes get in the way, especially when you are holding the camera vertically. To me, this was a minor problem but at times a frustrating one.
The battery pack adds weight. Depending on the person, this may or may not be an issue. Since this design is not permanent though, you can go back to using 2CR5 batteries if you find the mentioned problems to be too much trouble.
This modification requires that you cut notches in the battery cover and the battery compartment. If you are not comfortable with doing this to your camera, you should avoid this modification.

Canon EOS A2E With Battery Pack Built Into the Strap

1) Obtain four 2-cell AA battery holders at your local Radio Shack or electronic parts outlet. I would strongly recommend against getting the white open sided ones seen in the picture above. These battery holders have a tendency to develop cracks on the ends of the holders (which you can see happening with the bottom right battery holder in the 2nd picture above). A better option may be the black battery holders that are closed on 5 sides.

2) Sew a sheet of nylon fabric into the camera strap (sorry, I won't list dimensions. I will leave the placement of the batteries, the resulting sheet dimensions, etc.. up to the individual. Play around, experiment, and see what is most comfortable for you. I chose to have the batteries close to the end of the strap but most would probably want it a little further back so the batteries can hang over your hand when you are not wearing the strap around your neck). This nylon sheet will be used cover the battery packs. It should be able to wrap around the packs 1 1/2 times so make sure it is at least large enough for this purpose. Err on the side of excess, if it's too large, you can always trim it later.

3) Obtain adhesive velcro strips. Sew the loop strips onto the camera strap on both sides where the battery holders will be placed. Peel and stick the hook strips onto the bottom of each battery holder.

4) Make a dummy battery using an old 2CR5 battery:
   a) Start this buy cutting open the back (the flat side) of the 2CR5. Cut away just enough so that you can remove the cylindrical lithium cells. I found x-acto or box cutter blades heated over a flame to work best here (use pliers to hold the box cutter blade).
   b) Remove the cylindrical lithium cells from the battery. Attached to the cells are likely to be 2 metal strips which were used as external contacts for the battery. Pull these off, you'll need to use them again.
   c) Get a foot long piece of "speaker" wire and solder them to the metal contact tabs from step b. Clear urethane insulated wire with multiple copper strands is a good choice because it is flexible and has good abrasion resistance. 1 foot is probably longer than you need but any extra length can be easily wrapped and secured under the nylon cover sheet on the strap.
   d) Set the metal contact tabs from steps b & c into their old grooves in the plastic battery shell. The tab connected to the positive (+) wire should be on the left side so that it makes contact with the positive battery contact on the camera. You may have to use small sticks to prop and hold them in place.
   e) Mix enough epoxy together to fill about 1/3 of the battery shell and pour it in. This will make sure the contacts and wires are held in place. Let the epoxy cure according to it's instructions.
   f) Scrape off any epoxy which may have seeped over to the outer surface of the dummy battery's electrical contacts.

4) Wire the battery packs according to the following diagram:

Wiring Diagram for the Battery Pack

Here, four AA cells (2 battery holders) are in series on each side (left and right). The left series is then wired to the right series in parallel and this is tapped by the wire from the dummy battery. Make sure all connections are soldered for strength and insulated with electrical tape or heat shrink tubing to prevent shorting (remember to slip heat shrink tubing on the wire before soldering).

5) Insert batteries into the holders. The voltage at the contacts of the dummy battery should be 6V. Check it with a voltmeter to make sure before putting it into your camera. It may read a little more than 6V with fresh batteries but any reading over 7 volts would indicate improper wiring. Also check the polarity so that it matches with that of a normal 2CR5 battery.

6) Take the battery cover off your camera, put in your dummy battery, and lightly try to close the cover with the wire coming out the top corner. You won't be able to because of the flange on the battery compartment and the lip on the battery cover pinch the wire but mark these locations on the camera and battery cover with a pencil so you know where to trim the plastic.

7) Use a filing set or an x-acto knife to cut a notch in the flange on the camera's battery well and the lip on the battery cover so that the wire from the dummy battery can pass through.

8) Clean off the plastic particles left behind from making the notch and insert the dummy battery. Close the battery cover, turn on you camera, and make sure everything works. Remember the A2E needs the battery cover to be closed before it can receive power so you won't be able to turn it on by plugging in the dummy battery without the cover.

9) Attach the battery holders to the strap using their velcro surfaces. Leave some space between the upper and lower battery holders so the the strap can flex. Wrap excess wire under the nylon cover sheet and wrap the sheet around the batteries. Trim the sheet so that there is just enough to cover all the batteries 1 1/2 times. The sheet can be held in place by sewing velcro to the edges of the sheet at the points where it overlaps. Frays on the nylon sheets should be sealed by quickly passing a flame underneath.

Your camera can now be operated using AA alkaline or rechargeable batteries.

DISCLAIMER: The following information is for informational purposes only. No guarantee is made or liability assumed regarding the following information. Modifications you make to your camera are taken at your own risk. Because mistakes may result in permanent damage to your camera and any disassembly will void your warranty, it is strongly recommended that no attempts be made to modify cameras if you are not experienced in working with similar devices and unwilling to take the said risks.

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