Hey, here is more information: The device will be a braille decoder to be used inside a classroom in school. It will send data via Bluetooth to a computer. Expected use is about 4 tot 8 hours a day. Voltage is not yet determined as we have not set the specs yet of the device, it will either be: 3V8 and 3V3 => power supply 40mAh or 3V6 to 4V9 and 5V continuous (for USB) => power suply 125mAh