Using a Lipo with Monsterborg

I wanted to quickly write up my experience on using a Lipo battery with my Monsterborg. It may give others considering this some reassurance on approach. Objective for me was to not rely on having to manage lots of AA batteries, everytime I looked on amazon for batteries and a charger they normally came in packs of 8 (monsterborg needs 10), and so getting all what was required for running and simultaneously charging would not have been cheap.

In the hope that a Lipo would be a simpler approach, I read the following thread, and purchased:

• 1x Tattu 2300mAh 14.8V 45C 4S1P Lipo Battery Pack
• 1x SKYRC IMax B6 Charger
• 1x Charger power supply
• 1x XT60 Plug
• 1x Battery plug
• Solder, wires, insulation tape also required - Already owned

I’m not providing build instructions, this is not a how-to, rather a list of the components I used and my experience using them. When creating the XT60 <-> Battery plug connector cable, it's probably worth upgrading to some thicker wires to carry the load. There is no science in my approach, the existing wires hanging off the battery plug were really thin, so I replaced them with some thicker wires. ALSO, and I can’t emphasise this enough, check and double check you’ve created your cable correctly, getting the polarity right. Do this with a multimeter to be sure! I’ve attached pics of my connector cable.

I’ve really not done anything more than try the web example and drive the monsterborg forwards and backwards. Feel free to ask any questions, given I’ve not had much time to play with it since, I can say is ‘it works’, but I don’t have any knowledge of how long it works on charge for, if its optimal etc.

**Getting the wiring wrong:** I’m putting this info here in case anyone else, like me or theborg, gets the polarity of the Lipo wrong for the controller. The lesson I learned here is to use a multimeter. When creating my XT60 cable initially, I just mapped the polarity from what I could see from the supplied battery pack, somehow though I got this wrong. When plugging in the lipo there was a small ‘pop’ and a tiny amount of smoke, so I immediately disconnected it.

On initial inspection of the board I couldn’t see any obvious fault, I was looking for a melted component. First task was to pull the pi off the board and check that all works, I did this by powering the pi independently, it was fine. After reading this post from theborg, I then disconnected all the motors and decided to take another look at the controller, suspicion was that the DC-DC converter was dead. Hooking up a normal 9v battery and using a multimeter I could confirm DC-DC converter was fine; 9v going in and 5v coming out (phew!!). Inspecting further I could see some track was exposed and broken, figuring I had nothing to lose (would take days for a new controller board to be delivered to Germany), I soldered a jump cable from the capacitor to the pole which the track was seemingly connected to - it seemed simpler than trying to fix the track, I don’t have the pro equipment required for intricate jobs like that, and I wasn’t even sure if this would be enough to save the board. I am happy to report though, that after plugging in the pi, lights came on and the board was working!