![\"\"](\"https:\/\/blog.familjenjonsson.org\/blog\/wp-content\/uploads\/2017\/05\/2017-03-22-19.55.14.jpg\")
<\/a>This is what the Ballistic battery looks like on the inside. It’s just 4 A123 Lithium-ion cells in series. Should be a piece of cake to DIY.<\/p><\/div>\n
The battery cells are about $10 each, so it should be possible to make it for a lot less than it sells for… once you’ve acquired the necessary tools to make it, of course! \ud83d\ude09<\/p>\n
It so happens that I recently bought a 3D printer, a Lulzbot TAZ6<\/a>. I’ve been thinking that this would be a very useful tool to have for some time, and I’ve had a price watch set on Amazon. I’d seen on camelcamelcamel<\/a> (a very useful site if you want to get alerted to bargains on Amazon) that there would be occasional sales, so when I got alerted that the price had dropped by almost $400 from the standard price I pulled the trigger.<\/p>\n With the 3D printer, I had the capability to print a new battery case. This would have three advantages. First, as you can see above, I mutilated the old case pretty badly getting it open. Second, I could print it in a plastic that doesn’t melt if it comes in occasional contact with gasoline. And third, since the old battery was just on the hairy edge of being too tall, I could rearrange the cells to lie them down (like in the picture above) which would better utilize the space in the battery compartment.<\/p>\n This is the 3D-printed battery box, with the cells inside for test-fit. The hole in the lid is for mounting the terminals from the old battery. This lid had to be redone, as I had miscalculated the room needed for the terminal connections on the inside.<\/p><\/div>\n The next challenge was how to hook up the cells. The normal procedure for connecting battery cells is by spot welding a nickel strip to them. It is technically possible to solder them, but this imparts a lot of heat on the cells and you can easily damage them. The problem with spot welding is that I didn’t have a spot welder…<\/p>\n Luckily you can get Chinese spot welders for a bit more than a hundred bucks on ebay. They’re not exactly high quality, but for occasional use they should be perfectly fine. So I got one of those.<\/p>\n The only somewhat sketchy part about this is that the starter current is very high. These cells are rated for continuous 50A, 100A intermittent discharge current. Nickel has a much higher resistance than copper, so in high-current applications it’s not ideal. The Ballistic battery indeed had spot-welded copper connectors, but spot welding copper requires much better equipment.<\/p>\n I asked the people at batteryspace.com<\/a>, who I’ve bought Lithium batteries from before, and they said they used 0.3mm thick Nickel strips for their A123 cells without a problem, so that’s what I went ahead and used.<\/p>\n Here are the spot-welded cells ready for mounting. You really don’t want to accidentally short these cells, so I covered the connections with kapton tape.<\/p><\/div>\n Before spot-welding the final connections, I soldered those strips to the copper connectors going to the battery terminals. Then I just had to put the cells into the box and, voila, we have a new battery!<\/p>\n<\/a><\/a>