marco 
Dose anyone successfully connect a battery to mini2440? How? I need to make mini2440 portable.
battery
davef
Yes. Something that puts out 7.2Volt nominal should only be allowed to drop to about 6.0Volts (no load). A 5.0V 1AMP LDO should do the job, not counting any USB load. If you want to run USB devices as well increase the current rating of the LDO. I use two 7.2V NiMH in series running a 5V SMPS. To charge the batteries I put them in parallel and charge them from 13.8V with a constant current charger. I would do it the first way next time, as the SMPS didn't really increase the overall efficiency very much.
marco
Thanks davef, I'm not an expert in this field, I have a mini2440 and 7'' touch screen are there any tutorial to do this job? furthermore do you think that the usb car recharger could work as power supply?
davef
The first approach: - go to the National Semiconductors website and search for 5.0V LDO. They have application notes. To build it requires some electronic hardware experience. - you will need a charger. Search around for a either a trickle charger and manually terminate the charge when the cells get warm OR better still buy a proper fast charger for the cell chemistry that you use. I think USB powered hub is only specified to 0.5Amps, which would be marginal. The main thing to watch is that the voltage doesn't go above the maximum voltage rating of the touchscreen and whatever is specified as the maximum allowable voltage for USB devices.