Transplanting a mini helicopter battery

I bought a little 5 oz helicopter a few years ago. I played with it for about a month then it just sat in the drawer. Every few months I’d take it out and play with it once, then one day I put it in the drawer and never took it out again. That is until my daughter begged me to fly it a few months ago.

So I put it on the charger. When it was done I brought it out to the family room and was going to set it up for her to fly. I got it in the air and was in the process of trimming the rotors so it wouldn’t spin, when it started dropping. The battery died after 30 seconds of use. I put it on the charger and tried again. This time I couldn’t even get it more than 2 inches off the table before dying right away. I figured the battery must be dead.

I put it on my list to find a new battery and replace the bad one. I only paid $25 for the helicopter, but I figured I could find a battery somewhere for much cheaper. Then I forgot about it until a few days ago.

I found a two helicopter set at Savers for $5. They didn’t have a controller, but I figured since they had a manufactured in 2014 sticker on the bottom, the batteries had to be good. I got home and charged one. Sure enough it charged, but it didn’t respond to my controller. That was okay, I was planning on transplanting the battery into my helicopter anyway since mine was in much better shape (these two were beat up like they belonged to a 6 year old.)

I took the donor helicopter cab off to get to the battery, it was just a matter of removing 3 tiny screws. Once I had access, I desoldered the battery and removed it. Then I opened up the other helicopter and removed the bad battery. This battery was harder to remove because the positive lead for two of the motors were also soldered to the same pad as the battery.

To get every wire soldered into place, I ended up stripping insulation off all the wires that connected to the one positive pad and twisting them together, there was no other way to keep all three wires on the pad. Once this delicate operation was done I tried to see if the helicopter would respond. The lights came on, but it wouldn’t respond to the controls. On a whim, I decided to charge the battery again. Once it was charged the helicopter worked, sort of.

This time the helicopter would only fly about 2 inches off the table, but it didn’t die. I played with it for 5 minutes and the helicopter was still responding (when the battery dies, the helicopter just goes dead.) Now I’m not sure what to do. Maybe the rotor motors have gone bad. Maybe this battery was also bad, but in a different way. I put it back on the charger and I’m waiting to see what happens when I try it again.


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