As a heavy user of the Canon EOS film cameras, I can go through the designated battery in short order. Replacement batteries are expensive and getting more so. How can I be a film hipster and not break the bank??

Go rechargeable. Be as hip as you want and environmentally friendly.

The camera battery is called the 2CR5. It is a complex battery that joins two 123 batteries in series and gives an output voltage of around 6 volts. Rechargeable 2CR5s do exist, but are expensive and have a spotty operational history in the field.

In this instructable, we will disassemble a 2CR5 battery and rebuild it with cheap rechargeable cells.

Step 1: Destroy Your Discharged 2CR5 Battery

The 2CR5 battery is a lithium battery made of two smaller, 3 volt batteries (123 cells, popular with the high intensity flashlight crowd) attached in series to make 6 volts. In the specimen seen above, these batteries are clearly seen. Duracell and other battery manufacturers place a sticker label around the battery so the two cells are not easily seen. Simply peel off that label to reveal the cells.

1. Use a set of vice grips or pliers to grip the cell securely.

2. Twist the cell until the metal bands connecting the batteries break.

3. Remove the cells and any remaining metal contacts and send to the recycling center.

4. Retain the plastic shell for the battery.

*Note: Please only try this with a dead battery. There is a slight chance that the cells could short out and get warm or even start a fire if the battery is fresh. Unlikely, but as the electrical engineers on the Dreamliner will tell you, "Respect your batteries!"

Step 2: Add Contacts to Battery Shell

In this step, we will replace the electrical contacts that were attached to the original cells in the battery.

1. Fold a 1 inch by 1 inch square of aluminum foil to the width of the battery contact (about 4mm wide).

2. Thread the foil through the slots on the top of the battery.

3. Place a drop of cyanoacrylate glue (super glue) on the contact site and attach the folded aluminum foil to that site.

4. Trim the foil if needed to make a neat contact.

5. Repeat for the other electrical contact.

Step 3: Add Spacers to Battery Shell

I'm replacing the 123 cells with CR2 cells which are still 3 volts, but shorter. Therefore we will have to take up some space with a non conductive spacer. I used some closed cell foam from an old mousepad.

1. Cut a small piece of foam and fit into the top of the battery frame. Dry fit and trim as required to get a snug fit. You can glue the foam in or simply compression fit it into the top of the battery frame.

2. Fold the electrical contact material across the foam spacer and affix to the opposite side with some glue.

3. Cut and fit foam spacers for the bottom of the battery frame just as you did with the top. Since the CR2 batteries are shorter, I needed 2 thicknesses of mousepad to fit them snugly.

4. Once your bottom spacers are in place, glue a length of aluminum foil on the foam to connect the batteries electrically (in series). The negative side of the battery is slightly recessed, so I folded the aluminum foil a few times to ensure contact with the battery cell.

Step 4: Putting It Together

Once everything is set, it is time to put it all together.

1. Locate the + on the battery shell top. The first battery will go in that slot with the positive side (nipple side) facing up.

2. Put the other battery in upside down from the first (negative facing up).

3. My batteries were snug and did not move easily. If you feel you need some extra security, wrap a piece of electrical tape around the battery to ensure the cells stay in place.

4. If you have a volt/ohm meter, check the battery assembly to ensure you have the correct voltage and polarity. The battery assembly will run a little "hot" on the voltage because there is no load on the cells. As long as it registers at or over its rated voltage (6 volts), you are probably good.

Step 5: Operational Tips and Tricks

The moment of truth.

1. Insert your battery assembly and see how the device reacts. In this case, my Canon EOS 10s responded as normal and operated as expected.

2. Recharge when needed.

Tips and Tricks:

1. I used 2, CR2 batteries for this hack. Not a bad choice since they are 3 volts like the cells they replaced, but not as tall as the 123 cells they replaced. In the battery world, bigger usually means more capacity. So, I can expect a shorter life than if I replaced the cells with rechargeable 123 cells.

2. If you have rechargeable 123 cells, you can use the same technique, but the spacers would be a little different.

Enjoy your fully rechargeable 2CR5-like battery!