An external battery is useful for taking extra photos and videos as they have a higher capacity than the LiPo batteries that come with your camera. They can also replace difficult-to-find batteries in your backup cameras which you may sometimes use for your projects. Because they are cheaper on a watt-hour basis, you can bring several cells on a long trip. You can even take apart a laptop battery for a free Li-ion cell. I will be using my 2MP Canon S330 model as a working camera.
Battery size: 18650 rechargeable Li-ion
Capacity: ~2500 mAh (versus 1000 mAh)
Options for using NiMH AA batteries
Also suitable for cellphones
Step 1: Things Needed
Digital camera (an inexpensive one is recommended)
18650 li-ion battery (eg. used laptop batteries, Deal Extreme)
18650 li-ion battery holder
Camera battery (used to match the size)
2 pin connectors
Heat shrink tubing
Quick setting epoxy
Small copper or brass sheet (any metal that can be coated with solder)
Multimeter (to ensure correct polarity)
Sanding and grinding pieces
Saw (circular saw preferred)
Quick setting epoxy
Hot melt glue gun
Step 2: Cut Wood Into the Shape of Your Battery
Mark the battery's dimensions on the wood and cut it. A circular saw would make a smoother cut than that of a hand saw's. The block can be cut a bit wider or longer. You are going to sand it anyways.
Warning: When using power tools, always wear eye-protection.
Step 3: Grind and Sand the Wood
Use a coarse grinding disc to trim the wood until it fits the battery compartment. Use sandpaper to smooth the surfaces.
Step 4: Drill a Hole for the Wires
Drill a hole to lead the wires out of the plastic flap of the battery compartment.
Step 5: Mark the Contacts
Mark the "+" and "-" contacts on the wood. The battery pack may state the polarity but if it does not, you can test it with your multimeter.
Note: The T (thermistor) terminal was left out for my camera. For some models, it will work fine but others may require you to sacrifice a used battery pack with the circuit board inside. You will have to take out the LiPo battery and wire the 18650 holder to the circuit board so that the polarity matches.
Step 6: Make the Grooves
Make grooves for the wires and contacts by grinding it.
Step 7: Cut Metal Strips
Cut them the size of the original battery contacts.
Step 8: Solder the Metal Contacts
Thread wires through the hole first. Tin the metal strips before soldering them to the connectors with the correct polarity.
Step 9: Glue Contacts Using Epoxy
Glue the contacts with epoxy and use a clamp to hold them in place until they set. Make sure they are lined up properly.
Step 10: Solder Connector to 18650 Holder
Step 11: Test for Correct Polarity
This is a very important step. Before installing it, test the polarity with a multimeter so that it matches that of the original battery pack. Reverse polarity can damage your camera. Always make sure that the battery is correctly inserted into the holder. To make it easier to identify the polarity, you can add a blob of solder onto the positive terminal.
Step 12: Install Adapter Into Camera
With a 18650 cell, you can now take more than twice as many photos on a single charge. To increase the capacity further, simply install them in parallel. Multi-cell 18650 holder can be modified for parallel configurations. Two cells in parallel would double the capacity and make it useful if your camera will be on all day. This might look like an overkill but since aged batteries have a higher internal resistance and reduced capacity, it may work.
Other chemistries like 3 NiMH AA cells will also work. They have similar capacity and voltage.