Practical designs: 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-ion battery, 3 - lithium ion battery, storage battery, water battery and more; Note: they can not be applied for lithium iron phosphate batteries, 1 - 2 Li batteries in series and over 15 Li batteries in series LCD Digital display: the battery capacity gauge indicators come with PVC waterproof screen protector with bright 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 meters with alarms can be applied to different machines and places such as garden, home, office and more, durable and can serve you for a long time, meeting your different needs and practical battery indicators will give you nice experience Package Content: you will get 4 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 accurate 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: 4 x Battery meter Note: they cannot be applied for lithium iron phosphate batteries, 1-2 Li batteries in series and over 15 Li batteries in series. Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.