Practical : the battery capacity voltage indicators are designed with switched function button, you can press to check the cattery capacity or real-time voltage and turn off, with alarm design, the battery meter display will flash when the battery capacity is lower than 20 percent Fit for different battery: the batter gauge indicators are compatible with 12V/ 24V/ 36V/ 48V/ 60V/ 72V/ 84V lead acid battery, ternary lithium battery, polymer lithium- battery, 3 - lithium battery, storage battery, water battery and more; Note: they can not be applied for lithium iron phosphate batteries, 1 - 2 batteries in series and over 15 batteries in series LCD Digital display: the battery capacity gauge indicators come with PVC waterproof screen protector with green back-light, which makes you can read the results on the clear LCG display from different angles, low working power consumption and the max is 5 mA Wide applications: the battery with alarms can be applied to different machines and such as garden, home, office and more, durable and can you for a long time, meeting your different needs and practical battery indicators will give you experience Package content: you will 2 pieces of battery meter with alarm, convenient for your use and replacement needs, the working voltage input ranges from DC 12V to 84V, they can automatically detect to the voltage according to the battery voltage Specifications: Working temperature: 0-40 Display: capacity/ voltage Back-light: Green Product dimensions: 2.41 x 1.31 x 0.53 inches/ 61.3 x 33.3 x 13.5 mm Mounting hole dimensions: 2.3 x 1.12 inches/ 58.5 x 28.5 mm colour: black Material: ABS Package Contents: 2 x Battery meter Note: they cannot be applied for lithium iron phosphate batteries, 1-2 batteries in series and over 15 batteries in series. Only the above package content, other are not included. Note: Light and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.