Hey guys, I’ve been playing fast and loose with these batteries for some time. I have them in my kids Power wheels. I get a new set each year when they go on sale 2/for 80-100$. These things are great for the power wheels. The 18V kicks the kids around a little quicker and makes them smile a about 1.5X more than the 12V batteries they came with. One older power wheel is a 6V “quad” so the 18V makes that one really cruise at 3x original speed. So… Long story short, I tried putting two of these batteries in series to get 36V… and well it took off when she hit the gas and then less than 1 full second later stopped. The lights no longer lit on the test button on one battery, so something cooked. I took it apart and it seemed there was some diode that was shot. Like an idiot I tried it again… got the exact same result. One battery gets nuked each time. Not sure if it’s the load… So… be careful putting these in series. Expensive mistakes. I even used these 3D printed caps, which actually end up melting due to the current being so high.
http://www.instructables.com/id/Ryobi-Battery-Power-Source/
Inductive kickback from the motor most likely.
Tools have protection against this.
A raw motor does not.
Also there’s this guy:
Ryobi battery Build - Am i ready to test?(update: success) | Endless Sphere DIY EV Forum
So what I’m wondering is- what am I doing wrong… do I need to have 4 batts? two parallel and two series? Or would some big old diodes on the main terminals prevent the issue I’m having? I know just enough to make these really dangerous, but not enough to fix them when they’ve stopped working… Any help greatly appreciated, I’d love to be able to put two of these in series to get 36V for these bigger power wheels. Thanks!