DIY Lithium Battery Power Supply Upgrade

If you are interested in DIY lithium battery power supply, you might want to take a look at this article.

If you just happen to have a ZT102A original device with a dead built-in battery, then you might suddenly come up with the idea of replacing it with a lithium battery.
If you also happen to have a battery and a charging board, you can choose a battery size that fits the space after removing the original battery compartment, aiming for the largest capacity that can fit.

First, you install the charging board. You cut a discarded 7-segment display tube to use as a board holder and fix it at the bottom with double-sided tape.
The pins of the tube can be soldered directly onto the pads of the board.
You should note that the two pins of the discarded display tube must be completely isolated with zero resistance to each other.
You position it so that it is soldered onto the positive and negative output terminals of the board pads.

Then you install the battery wiring.

For the red and blue indicator lights, you drill two small holes in the back shell at the corresponding positions.
You seal the inside with hot melt glue, and then use a black plastic sheet in the middle to separate the light paths of the two LEDs.
In this way, the light coming out from the two holes on the back will not mix.

Done. The display is really bright.
Because there is no series transistor voltage drop in the charging board output, the backlight is made brighter.