Battery power...

Up to now I have been using 6AA 2000mAh rechargeable batteries to power the RPi, this gives an uptime of about 3.5 hours estimated current draw of 575mAh. Obviously not that good for a modern phone. I have now purchased a 12000mAh LiPo rechargeable "phone extender" type battery. Unfortunately this measures 10.5x10.5x2.5cm and won't fit in the phone casing, but should give (12000/575) 20 hours of operation.

On the LiPo there are 2 USB outputs - one 5.0V @ 2.1A for iPad type devices and one for phones. The Pi plugs directly into the 5v 2.1A  output and works a treat. The other output is 5.5V @ 1A and is labelled as being for phones - it even comes with a Nokia 2mm adapter. Great this can power and recharge both Pi and Nokia. Unfortunately, although the Nokia initially appeared to charge form the LiPo, it keeps displaying "Charger not supported" and stops charging. Not sure whether this is the 5.5V not being enough (the original Nokia charger outputs 7V) or something else.

I am going to fit a usb to Nokia charger then expose a USB socket on the side of the phone so at least the nokia can be charged without dismantling the whole thing. Having said that the Nokia standby seems to be about 5 days!

The battery won't fit in the case so I have decided to put it under the phone. I put 4 small plastic feet on the bottom so the phone now sits on the battery - not ideal but not much choice.