The UPS(Uninterrupted Power Supply) Kit is designed specifically for the ODROID-M1S.
It is equipped with a 18650 rechargeable Li-Ion battery holder, charger control IC and a 5Volt Boost DCDC.
There is a small MCU on the board which measures the battery level and communicate with the ODROID-M1S board via USB interface.

When the AC power source is removed, the UPS keeps supplying the power to the ODROID-M1S boards with the battery.

The M1S-UPS has a USB serial port(ttyACM) to communicate with so that it can trigger the shutdown process by sending a low battery warning.
It will significantly reduce the risk of data loss by sudden power loss.
When the AC power source becomes available again, the UPS will supply power to the ODROID-M1S again and trigger a power-on event automatically.

Specification

✔ The battery is not included in the package, so you have to buy a PROTECTED 18650 Li-Ion rechargeable battery in your local market and install it.
The length of the 18650 Li-Ion battery with a built-in protection circuit is close to 68mm, which is about 3~4mm longer than the unprotected bare cell battery length of 65mm.

• Since the retail market in many countries, including South Korea, does not allow the sale of unprotected lithium-ion rechargeable batteries, we designed it to use batteries that include a protection circuit.
• For safety reasons, when purchasing batteries, please choose a reputable battery cell manufacturer if possible. As far as we know that Panasonic, LG, Samsung, and CATL are famous.

✔ Due to the Li-Ion chemical characteristics, the battery voltage level might go higher slightly when the load is very light.

WIKI : https://wiki.odroid.com/accessory/power_supply_battery/m1s_ups