Stick with soldering irons, soldering guns have their place, just not in an RC tool box. Ok, maybe they are good for soldering large wires, but their place is not on the end of your nice new $80 battery pack.
For soldering batteries, here are the steps that I use to keep from roasting my cells. My favorite is to use a dremel with a large sanding drum, but just a peice of 100 grit sand paper will work fine.
1. sand the ends of your cells. This exposes nice fresh metal and IMO gives the solder something to grip onto. In my years of racing, this has proven more effective in keeping the solder attached to the end of the cell than anything else.
2. Pre-tin the ends of the cell, clean the tip. Do all the positives, then do all the negatives. This will allow each cell to cool between each soldering session. It doesn't take a ton of solder to pre-tin the cell. You will only need a spot slightly larger than the flat on the battery bar.
3. Pre-tin a battery bar, clean the tip. Again, you are only trying to wet the contact patches on the bars. It will make assembly that much faster.
4. Beg, borrow or buy your own battery jig, it will make life that much easier. I hope Deans has finished re-designing their molds.. at least that was the excuse I was given for their shortage.
5. Assemble the cells in the jig in the order and facing the directions you want your cells, keeping in mind what side of your car the positive and negatives are.
6. Place a pre-tinned bar across the cell terminals and hold in place either with the jig or with a pair of needle nose pliers or push down on them with a small tool to hold the bar in place while you heat the joint.
7. I use a very small dab of solder on the iron to help transfer the heat to the joint faster, hold the flat of the iron as flat on the battery bar as possible for about 3 - 5 seconds. The joint should have re-flowed and wetted the bar to the end of the cell. You are looking for a small fillet between the bar and the cell. If that fillet of solder is there, you will have a low resistance, strong joint that will be ready for the rigors of racing.
8. Wipe the tip, let the iron recover* and repeat for each cell.
* Important step - let the iron recover between each time you solder. The reason to use an iron with a nice fat tip is heat storage. Each time you solder a joint, the heat is transferred from the iron tip to the items that you are trying to solder. If you have one of those nice fancy temperature controlled irons, watch the light or temperature reading to be sure that the tip has re-heated to operating temperature.
Think of the iron tip as a glass of beer under a trickling keg tap. There comes a time that the glass will not hold anymore beer. Same with the iron tip, therefore it is saturated with heat. As soon as you use that iron the heat level will drop off. Just like that glass of beer you just drank, under that tap eventually it will refill, you will just have to wait for it.
Speed Merchant Rev7, Tekin, TQ Racing (wire), Team Tamale
RC Excitement - Buy where you race, support your local tracks.