DIY Yandou Razor Battery Upgrade Guide

After several years of use, the internal rechargeable battery of a Yandou razor may deteriorate. So, what should you do about it? If you're interested, keep reading! You can upgrade the battery to a lithium-ion version for continued use.

The original charging setup uses an RC+T direct charge nickel-cadmium battery. It starts with a 104 CBB capacitor that reduces voltage and limits current before passing through a miniature transformer to output approximately 3V at 20mA for charging. As for whether the battery can be fully charged or if overcharging occurs, that's a common issue with typical 1.2V battery setups.

To modify the system, you need to remove the original voltage-reducing rectifying components. Then, replace them with a Sony 680mAh lithium battery on the existing PCB. The charging circuit should also be upgraded to a TP4056 module.

The key change is the voltage regulation. Connecting the battery directly to the motor isn’t advisable, as it can lead to significant wear and overheating. Instead, you can use an SC5832A voltage regulator. It accepts an input voltage of 2.5-6.5V and outputs 1.5V at 2A, effectively simulating a fully charged battery state while being gentle on the battery. The IC's 2.5V starting voltage serves as a low-voltage cutoff protection for the battery.

Circuit Diagram