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RE: Useful info - thanks

Those 5v USB battery packs for charging phones and other gadgets use batteries in the Li-Ion family. They also typically use a 'boost converter' chip, essentially a DC-to-DC switching power supply to regulate the output to 5vdc. This means you are not getting "ultra-pure" DC power directly off the Li-Ion battery but through the switcher. The output is no longer as 'clean' as what the battery cells may provide but dependent on the DC-to-DC switching chip and filtering.

This may or may not be important to you. An RPi doesn't necessarily require ultra clean DC power.

The nominal voltage of a NiMH cell is 1.2v so four of them in series in a battery pack will provide ~4.8v. However, the voltage is typically a little higher by a good 5% or more so the 4.8v battery will work for devices that require 5v.

For example, my 10Ah 7.2v NiMH battery pack showed about 8.2v right off the charger. That's 14% greater than 'nominal'. It measured 7.6v after powering a 0.25A (250mA) load for 18 hours. That's still 5.5% greater than the 'nominal' 7.2v.

If you apply the percentages to a 4.8v NiMH battery pack, it should be within range for powering a device that requires 5vdc.



Edits: 10/01/16 10/01/16
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