Materials List
Soldering Iron.
Two 12" bars or wood (more on this later).
60/40 rosin core solder. Sho Goo Glue or Silicon.
Battery bars, Shrink wrap, 12 Gauge Wire.
A quality battery connector (Deans or Anderson recommended). Dremel Tool or file.
Small brass rod about 6"

       First you need to decide what configuration your cells are going to be. The most common is the brick style. To keep the cells together while soldering and to add to strength, we are going to glue them together. You need to apply a small bead of Sho Goo or substitute. Run the bead of glue from the positive to negative terminal.

       Once you run the bead of glue, flip another cell around so it faces the other direction and attach them together. You should end up with something like this. While the glue is still wet slide the cells up against a wood board. Push each cell up tight against the board making sure everything is straight. Its time to take a break and let the cells dry overnight.

       At this point you can measure and cut your wire to the needed lengths. Once cut remove about 3/16" to 1/4" of the wire insulation on the end of each wire. Than twist the strands of wire tight. Now its time to tin the wire ends. Heat the end of the wire and apply a liberal amount of solder until the wire it totally covered and the solder has been absorbed into all the wire strands.

       After the cells are dry place them in your home made battery jig. Its simple, we need something that's going to help us keep the cells upright while we work on them. We use two pieces of aluminum about 1' in length. You can use longer if needed. Place one piece on each side of the cells. Than put an elastic around the end of the bars. Now your cells are in the middle of a tight cell sandwich. 

       You now need to give the solder a good surface to bite onto. There are several ways to do this. We use a Dremel tool with a fiberglass bit or sanding drum. Its very fast this way. Or you can use a file. Sand an area in the center of the cells about 1/4" in diameter, or wherever size you think solder is going to flow. If you use a file scar the area back and fourth making many "X" patterns in the metal of the cell. NOTE: Some of the new GP cells have a coating on the cells that DOES NOT need to be scuffed to solder to. As a matter of fact they solder better to if left untouched. Just clean any grease or oils from them with a mild solvent.

This is a picture of a untouched end of a cell. We need to etch this area to give the solder a good place to stick to.

This picture on the left shows what a fiberglass wheel does to the metal.

Right: This was done with done with a drum sanding bit on a Dremel tool. 

       At this point you can tin the tops of all the cells. I tin one whole side, than flip the jig over and do the other. To tin the cells apply the iron and the solder at the same time to the cell. This is a quick process. It should take about a second once you've done a few packs. Once a small amount of solder has melted on the cell, move it around with the iron tip in a quick circular pattern. Make the soldered area a bit larger than the battery bar you are going to use. About a 1/4".

       Caution, if it takes you more than a second or two at this point you can have future problems. The battery vents are under here and if the melt and seal up, you can be in for serious problems. Namely a battery that could explode!!!

       Now its time to put the battery bars on. Lay the bar on the top of the cell. I like to use a brass tube to hold the battery bar while I solder, because I know if the tube starts to get hot than the iron has been on the cell for to long. You can also use a screw driver here.

       Apply the iron to the top of the battery bar on the positive side, while adding a bit of additional solder. Very little is needed. It should take only a few seconds to solder the bar to the cell. Allow to cool off and make a good bond.

        Now that the positive end of the battery bar is soldered down good and tight, its time to move over to the negative side.

       Now all that's left is to add a good quality wire are connector.

       You can wrap your cells in shrink wrap to finish off the project. Cut a piece of shrink about 1" longer than the total pack length . Slip the cells inside and leave about 1/2" extra on each end. Use a blow dryer to shrink the wrap good and tight. In boats we like to skip the shrink wrap because it holds the moisture in. But make sure to cover the battery bars with something like electrical tape.

       When charging cells for the first time, make sure to charge at a trickle charge rate! This allows the cells to equal out better than if you were to blast them with a quick charge. I like to cycle my cells like this a couple of times prior to any quick charging.

       This article assumes that you have a basic knowledge of electronics. If you don't, consult a local hobby shop for help before attempting this.