Eco-friendly toys - conversion for 18650 LiIon batteries

thingiverse

Parents around the world face similar issues, including the problem of tonnes of batteries ending up in the trash from electric toys. My daughters also often get toys powered by traditional disposable alkaline batteries. So I often convert these toys to be powered by rechargeable lithium batteries. In this case I'll show you one of such conversions, based on the small mechatronic dog, named Łatek (eng. Dottie) :) <img src="https://i.imgur.com/vgdVjBJ.jpg" /> It was originally powered by 3, connected in series, C-cells. <img src="https://i.imgur.com/vkN8eww.jpg" /> So the operating voltage varied between 4.5 and 3V. That voltage range is covered very well by lithium cells rated at 3.7V. When converting toy dog I didn't want to strip its ability to be powered by ordinary alkaline cells, so new power module is made to fit the factory electrical contacts. <img src="https://i.imgur.com/G8IABAm.jpg" /> The new power supply is based on low-cost TP4056 module, which is responsible for charging from USB-C port and has a circuit to protect the battery from discharging below 2.5V. <img src="https://i.imgur.com/8QqZ3rE.jpg" /> The wiring diagram is very simple and does not require much skill other than using a soldering iron. <img src="https://i.imgur.com/z3yYyY6.jpg" /> You can use any LiIon batteries with a nominal voltage of 3.7V for conversion. These do not have to be 18650 batteries, for example, you can use batteries from your old mobile phones or e-cigarettes. Think eco-friendly :) I used two 18650 batteries, because I had such on hand. I connected them in parallel to increase the total capacity, which prolonged the fun with the dog. Remember that if you want to connect two batteries in parallel, they must be charged to the same voltage! Otherwise you could cause an accident, even a fire! My power source is using commercially avaible battery contacts in size 12x12x0,2mm. <img src="https://i.imgur.com/5QR0LPR.jpg" /> <img src="https://i.imgur.com/r7kMt6q.jpg" /> I'm sure not many of you have exactly this dog among your toys, but this project is primarily intended to show you a way which will, in effect, turn your other toys to be more eco- and wallet-friendly. Good luck!