this product is fully functional, you can display the battery voltage, battery power, you can also plug directly into the phone or other 5V equment charging.This product is suitable for all kinds of outdoor power, mobile power, instrumentation and other equment additional battery power voltage display and additional USB to charge the phone and other functions.this product s synchronous rectification step-down scheme, low heat, energy saving and envmental protection.This product is compact in structure, ing full of space and reducing costs.Static input current: 5-25mA, the lower the battery voltage, the smaller the current.USB output: 5V/2A (a USB setting for recognition, a setting for Android recognition)USB buefficiency is up to 96% (beca of the synchronous rectification circuit, the buconversion efficiency is high and the heat is low.8 segment power resolution: 10% 25% 40% 50% 60% 75% 90% 100%The accuracy of the is about 2%working temperature: -10 ~ +65 ° CWorking humidity: 10~80% (no condensation)Display Type: Dial OnlyModel Number: DL-USB-02Operating Temperature: -10~65Accuracy Cla: 1%DIY Supplies: ElectricalPower Supply: DC12.6VColour:blackSize:45 x 26 x 18mmMaterial:plasticPackage Contents:3 x dial display Only the above package content, other products are not included.Note: Light shooting and different displays may ca the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.