Battery charge level is determinable on GW-BX5600 (and GMW-BZ5000) via voltage data in diagnostic menu
November 2, 2025
Image by G-Friends
While the GW-BX5600 and GMW-BZ5000 do not have a battery level indicator on the main display (but have a low battery indicator and a battery level indicator on the Bluetooth-connected Casio Watches smartphone app), a G-Friends video (at youtube.com and embedded below) shows that the GW-BX5600 has an on-watch menu with a selection for battery information where the voltage is displayed. The menu appears to be a diagnostic menu, not mentioned in the instruction manual, that is accessed by pressing the A,C, and D buttons simultaneously (or the two left buttons and the lower-right button).
The voltage information provides an indication of the charge state of the watch, but which voltage levels correspond to the indicator charge levels seen on other Tough Solar watches? We asked Perplexity AI and it seemed to give a satisfactory answer: High is 2.6 to 2.7 volts, Medium is about 2.3 volts, and L is approximately 2.0 to 2.3 volts. The watch in the video shows 2.4 volts, so this would correspond to a medium level charge. We don’t know if the “M1” next to the voltage indicates the charge level. If it does, this means that there is a battery level indicator on the watch, just not on the main display and not really officially. Keep in mind that AI can sometimes be wrong, so use this information at your own risk. Also, pressing three buttons at once every time you want to check the battery level may be less convenient than setting up Bluetooth and using the smartphone app.
What voltage thresholds does Casio use to determine the charge level of a CTL1616 battery?
Perplexity AI:
Casio uses the CTL1616 rechargeable lithium coin cell battery in its solar-powered watches, including some G-Shock models. The charge level determination internally is based on voltage thresholds within the battery’s operating voltage range of about 2.0 to 2.7 volts.
Though Casio does not publicly publish exact voltage cutoff points for the L, M, H charge states specific to the CTL1616 battery, these thresholds are generally understood as follows:
High (H) battery level corresponds approximately to a voltage near full charge, around 2.6 to 2.7 volts.
Medium (M) battery level corresponds roughly to the nominal voltage, about 2.3 volts.
Low (L) battery level is near the minimum safe discharge voltage, approximately 2.0 to 2.3 volts, where the watch begins disabling non-essential functions to conserve power.
These thresholds align with the CTL1616’s nominal voltage of 2.3V, charging voltage near 2.6-2.7V, and cutoff around 2.0V. Casio’s watch electronics monitor the battery voltage and classify the charge state accordingly to manage watch functionality and power-saving modes.
In summary, Casio’s charge level states for a CTL1616 battery are voltage-based thresholds roughly at:
H: ~2.6–2.7 V
M: ~2.3 V
L: ~2.0–2.3 V
This scheme helps the watch safely operate and extend battery life while providing the user with a basic charge level indicator.
G-Central Note: We would have liked to credit whoever figured out the voltage thresholds, but all of the listed sources were only CTL1616 battery information pages and a Casio manual, none of which disclosed any voltage thresholds for the different charge levels, so we should probably just thank Perplexity AI.
Disclosure: G-Central is an independent fansite supported by ads. We may earn a commission on sales from our links to external sites labeled with "affiliate link." Prices in articles are USD unless otherwise noted. Japanese yen prices include tax. Please follow your country's official G-Shock site for release updates.
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