Making battery packs requires your full care and attention.

You are working with a lot of stored energy and pretty much all the tools you use are metal and can cause a short circuit. In a short circuit, something is going to get hot, and probably melt.

I’m the first to say batteries are dangerous. I always advise using caution and being aware of where your tools are at all times. I’m also one to admit I have made mistakes and had a few significant shorts. None have been explosive, but they all make you jump.

The hand picture above was a pretty benign incident. I was check the voltage on a pack with a volt meter and had the probes in an XT60 connector. The probes shorted together and poof!

This didn’t occur while building the battery but while fixing it. Fixing batteries is much more dangerous than building them in the first place. To be honest, this one really shouldn’t have happened, it was a moment of pure stupidity and luckily I was unharmed. The battery wasn’t harmed either, though the BMS Mosfet board got cooked pretty good.

I had the clamp oriented away from the battery, but it wasn’t laying flat. I moved it, started to solder and it contacted the negative rail of the Mosfet board.We can all see a few ways this could have been avoided. Enough said.

The first welder I made was this microwave transformer based welder. I have more on this in my post about battery tab welding here, but basically microwave transformer welders heat of battery tabs very slowly. If you use thick tabs, you can end up heating the battery too much. Too much to the point the battery chemistry becomes unstable and pressure builds up in the battery and it vents out the top, rather violently. It left a burn mark on the welder, landed on the epoxy floor and burnt a hole in that too. The smell was pretty terrible and took quite a while to clear out.

Many people have used these welders successfully but I believe them to be inferior to capacitor based welder and only suited to welding thin battery tabs when no other option exists.

About 2 years ago I made a quad copter. During a test flight, a quick release prop failed and the copter crashed. The LiPo caught fire and cell after cell burned until there as not much left. The copter was heavily damaged but some parts were salvaged. I’ll make a post about the copter and give a full story. Again this just goes to show, batteries can be dangerous so be careful