DIY modification of small electric motorcycle 12V battery/car MP3 is really cool!

The original " audio " of my son's small electric motorcycle can only produce music , such as horn , whistle and alarm . The battery is 6v4Ah, which is not very durable. It ran out of power when I rode to the park, and I had to pull it with a rope when I came back.

Later, at the unanimous request of my family, I took on this renovation task... I wanted to replace it with a better 6v battery, but after a round of research, I found it was quite uneconomical. So I simply replaced it with the 12v12Ah battery that I had discarded from my previous electric bicycle.

The original car uses a 6V motor, and the 12V voltage needs to be reduced to be suitable. At first, I tried to use the method of connecting diodes in series, but later found that it was not feasible at all. Since the current is quite large when the motor starts and the resistance is large, about 6 or 7A, the simple voltage reduction is abandoned, and the switch circuit is considered to reduce the voltage.

While looking for materials, I found a brushless electric bicycle controller and took it out to study the circuit. This saves a lot of trouble! The controller was originally used on 36v electric vehicles, with undervoltage, overcurrent, and speed regulation functions . It was slightly modified to be used on 12v circuits, and all functions can be retained - protection below 10v, current limiting greater than 7A, and using adjustable resistors to replace the original Hall handle to adjust to the appropriate position to adapt to the 6v motor.

Controller schematic diagram:

Later I changed it to a speed reduction circuit board:

The battery and the speed reduction plate were finally installed. At the same time, the original music disc was removed and planned to be upgraded, and the speakers were also installed inside.

I happened to have a discarded 1G car MP3 player (the kind with FM transmitter function that plugs into the cigarette lighter) on hand. I took it apart and studied its internals. It uses 5V voltage and tests that the current is not high in working state. That's easy. 7805 is enough for it. Just make a hole in the appropriate position to fix it. Hot melt glue can make complicated things very simple!

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The 5V power supply and amplifier of the perforated board (taken from an obsolete megaphone, the kind used by the neighborhood committee aunties):

Amplifier IC is the "famous" 2025:

The USB interface is directly connected with a USB cable, which makes it convenient to plug into a computer to download songs.

The audition is OK, very flavorful.

I downloaded more than 100 nursery rhymes, which is enough for me to listen to. I took it home and my son rode it around the neighborhood. He was so good! A group of kids were chasing after him, and many parents came to study how it was done. It was so cool! It also has a large battery. I tested it and it can last for two hours. The original battery might not last for 20 minutes.