Features: Easy to operate. Mini and compact. High quality material, durable in use. Please do not use this product outdoors. Not waterproof Universal for DC5-30V 12V 24V 3 Series Lithium Lead-Acid batteries. Specifications: Material: Plastics Size: Approx. 46x15x3mm/1.81x0.59x0.12in Working Current:10mA Display Mode: LED Indicator Working Voltage: DC5V-30V Note: Please do not exceed the operating voltage, which will damage the product. Function setting description: 1. Press and hold the key for 2 seconds to enter the setting state: the mode light (battery type) flashes, and the string number light usually on; Press the key briefly to select the battery type. 2. After confirming the battery type, long press the key for 2 seconds to enter the serial number/voltage setting (the mode light usually on, and the serial number/voltage light flashes). 3. Press the key briefly to set the number of strings or voltage of the battery; Please refer to the above table option settings for detail. 4. After setting, long press the key for 2 seconds to save data and return to the displayed power state (or wait for 5 seconds to return automatically). 5. In the setting state, if there no operation within 5 seconds, it will automatically return to the normal display of power. In the normal display state, if there no operation key within 10 seconds, the product will automatically turn off the display and enter low power consumption, or you can manually press the key briefly to turn off the display and enter low power consumption; When the product turned off, press the key briefly to turn on and display the power. Package includes: 1x Battery Meter