# Pandora battery life with USB devices

#### lobski

##### Member
I'm wondering if there's a way to calculate the battery life of the Pandora with USB devices hooked up onto it. Obviously having a hard drive or a decent USB device will greatly reduce the battery life, if it's not hooked up. Hard drives, or any device that requires large motions would probably be the biggest battery drainers.

I have no idea (And I've searched) but has there been discussions on the limitations of the battery life with heavy USB devices hooked up to it? (With the sole power being the battery)

This is something you could work out for yourself, as long as you know how much current the kit you want to use draws. According to the wiki, the battery which will come with the Pandora is rated at 4000mAH. It will supposedly run for about 10 hours on this, so the current drawn by the Pandora itself would be about 4000/10 = 400mA. Add to those 400 mA the current required for the USB devices you have in mind, then divide 4000 by that total for the number of hours.

For example, if you have one device which needs 100mA and another which uses, say 200mA, the total would be 400 + 100 + 200 = 700mA. The 4000mAH battery will run this lot for 4000/700 = about 5.7 hours.

If you can't find the exact power specification for your devices, you can still make a decent guess by substituting the requirements of a similar device.

The max USB power transfer is 500mA, you could also say that at 500mhz you could charge the Pandora faster than it uses the battery or 8 hours charge time via USB while not in use. Ff clocked higher and under heavy load, the Pandora would use more power than is provided via USB and the battery would drain. AC charging ftw (a little off topic.....)

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