Battery quit on my dirt bike, so instead of spending $100 for one, I built my own (which is actually over 3X more powerful than most $100 packs). This is ONLY for running the accessories, NOT starting the engine (I have a kickstart).
If you shop around a little more, you can find better batteries for much cheaper. Make sure they're rechargeable nicad or nimh (NOT lithium).
Step 1: Buy the batteries. You will need 10 total (do NOT use more or less in one pack). Make sure they're rechargeable Nicad or Nimh. You CAN NOT use regular alkaline or lithium batteries.
Step 2 (VERY important): Fully charge each battery with the same charger. If you don't have one, buy one. They're cheap. If you fail to do this, the batteries will have an uneven voltage, and some will overcharge when you charge the finished pack.
Step 3: Glue them together in PAIRS, mirroring each other as shown. I glue pairs first because I bought 3 packs of 4 batteries, which left me with 2 extra. That way if I screwed up somehow in step 4 I could use the extra ones.
Step 4: Solder one side of each pair as shown. In the video, the black/gray side of the batteries are positive, while the green side is negative. Do NOT solder both sides, as you will short circuit them. You now have five 2.4 volt batteries.
Step 5: Super glue them together. The best way for me to describe this is to look at the 2 pictures at the end of the video. Pretend the other side of MY battery pack has no solder points, and your pack should look exactly like this on one side, empty on the other.
Step 6: Now turn the pack 180 degrees on the table, and solder the terminals exactly the same, except this time DO NOT solder the vertical side on the far left. These will be positive and negative wires. (WARNING: If you solder those last two together you sill short circuit the battery and probably cause a fire).
Step 7: now solder on your positive and negative wires (The battery is now 12 volts, so BE SURE not to let the wires touch. Also DO NOT let ANY of the other wires come into contact with metal or one another). Test the output (should be a little over 13 volts), and tape 'em up good, and you're all done!
