Power-up Victory 890C: Li-Ion, 9999 Display, More

How to modify the Victory 890C multimeter to enable lithium battery direct supply and increase the frequency and duty cycle display of 9999?

On the hardware side, the modification involves changing to lithium battery direct supply, removing the low voltage prompt indicator, lowering the buzzer volume, reducing the backlight brightness, and improving resistance measurement speed. On the software side, the automatic shutdown time is adjusted to 10 minutes, the backlight brightness time is extended to 30 seconds, the display is changed to a four-digit 9999 display from the previous three and a half digits. Additional features include adding an AC 200mV range, frequency measurement range, and duty cycle measurement range. Other features like square wave output haven't been added due to differing versions, coding addresses, and functionalities. Adding these functions is quite complicated and could only be achieved through multiple attempts of disassembling and reassembling the 24C16A storage chip. 

This is the 08 version from 2012.

The buzzer's current-limiting resistor is changed to a range of 500 to 1000 ohms, reducing the harshness of the sound and saving power.

In terms of hardware changes, the resistor for the buzzer on this diagram is marked incorrectly. The previous diagram is accurate. For lithium battery direct supply, all you need to do is connect the positive terminal of the lithium battery to the output pin of the voltage regulator chip (to the left of the "HOLD" button). The added capacitor here is blocking it. The resistor on the right is for screen brightness, increase it to 500-1K to lower the brightness.

The modified data for the 24C16A storage chip allows the added function ranges to be toggled using the "HOLD" button. The original functions are still available, and the DC current and AC current 2A ranges can also be tested with the function codes. If you find these features unnecessary, you can choose not to include them.

The added AC 200mV range is included in the transistor range, mainly to accommodate occasional resistance tests for the accessory impedance tester.

For measuring motorcycle batteries：

In the capacitor range, frequency measurement is added, which can also be used for calibrating the impedance tester frequency.

In the 20M ohm range, the duty cycle measurement function is added, which can also be used to test the impedance tester's duty cycle.