User guide

M3 SKY

M3 Backup Battery

Real Time Clock (RTC) Summary

A secondary backup battery is integrated in all M3 SKY terminals. The secondary battery is used to keep the

time and date information while changing the main battery. However, its functionality varies according to its

model and the version of main board.

In early models of MC-7XXXS, a small real time coin battery was included as shown on the below left picture.

Left figure shows integrated (soldered) RTC coin battery and the right figure shows a detachable backup

battery.

In main boards v1.1 (MC-71XXS), v2.1 and v2.2 (MC-75XX/77XXS), the coin battery is charged through

system power. Hence, if the terminal is turned off by pressing the power button for 10 seconds, the system

stops operating and consequently the coin battery is not working. Therefore, the RTC is reset.

To charge the coin battery, the main battery must be attached to the device AND the device is switched on. If

the PDA is not switched on, the coin battery is not charging even if the main battery is attached. Moreover,

placing the turned off terminal on the cradle will NOT charge the coin battery.

To prevent RTC reset, you must not turn off the terminal by pressing the power button for 10 seconds.

In main board v1.2 (MC-71XXS), the coin battery is charged through the main battery and it follows the main

battery level. Hence, turning off the terminal by pressing the power button for 10 seconds will not reset the

time information. But leaving the device at off state for longer than 5 minutes will reset RTC and GPS data

because a fully charged coin battery is only able to keep RTC and GPS data for 5 minutes. This also implies

that stored data will reset if the main battery is detached for longer than 5 minutes.

As improvement of the backup battery system is necessary, M3 Mobile re-designed the backup battery