Here i will explain how you can make your own battery packs for just a couple dollars.
Step 1: Figure Out What Capacity You Need in a Battery
When searching online a lot of options exist out there. What are you looking for? Many NiMH batteries are sold with tabs on them capable of being soldered. If not, dont fear they can still be soldered using the proper equiment.
Step 2: I Chose
I wanted the highest capacity i could find without exceeding the AA battery size. I found 3000mah 1.2v. It is inportant to know the size as you will find some may be C or D and incompatible with your application. Considering how they will be used is important. As you can see in my photos i used either 4 AA NiMH cells together or 5 cells together depending on my application which are used in RC cars. Space is the limiting factor here. 4 batteries is 4.8v and 5 batteries in series is 6v.
Step 3: Assembly
When assembling in series the process is relatively simple. You will solder the ends back to back positive to negative. If you were running them in parrelel you would run two side by side and solder positives together and negatives together thus doubling the capacitance to 6000mah and maintaining the voltage at 1.2v. In my case that wouldnt suffice however you may have an application like that which would work for you. Before you start soldering you will want a hot glue gun and electrical tape. Tape the four batteries in the shape you are looking for and squeeze hot glue down the center of the batteries and wait a few moments for it to set up. Once done you are ready to solder. This requires a very hot soldering iron. You will want a wells gun or similar. You need it at full temp when applying solder and wire so it can be done quickly with a lot of heat yet not leaving the soldering iron on the battery for any extended amount of time. This could damage the cell. Take small 3/8-1/2" sections of wire and solder the ends back to back until you have 4 batteries in series. If using 5 it gets a little trickier and requires an additional 2" section of wire as one battery will be faced the wrong direction. You will need a battery connector capable of connecting to your device and charger. I use jst connectors for my application and buy them online for $2-3 for a pack of 20. Pick your end and make sure it is polarity correct. After soldering is conpletely finished take hot glue gun and cover all soldering joints. If you ran a 5 cell battery glue the extra loose wire along the seem where battery runs. You may at this time want to run a bead of hot glue in the remaining seams for added stability. After its done you can use battery. If you want further stability and cosmetic beauty add a large piece of shrink tubing over entire pack and use a heat gun to apply and wallah a professional looking finished battery pack. If you shopped right this cost you about $1.50-$3 to make. A huge savings over retail packs and you probably doubled the capacity of what is offered out there.
Step 4: What You Need
1.) Soldering iron
3.) heat shrink
4.) rechargeable NiMH batteries
5.) elwctrical tape
6.) jst or end connector
7.) soldering station
8.) hot glue gun
9.) 2 tubes hot glue
10.) 4" electrical wire