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In Reply to: RE: Useful info - thanks posted by Audio Bling on September 30, 2016 at 16:51:24
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 10/01/16Follow Ups:
I see from your source that an equivalent 5V NiMH battery pack would run about $67 + charger.
If you buy a battery from them, you have to be careful to choose the right connector type for the battery and/or an adapter cable for your device as well as the charger.
I had to DIY a USB to barrel one for the Jackery to fit the Touch.
Why would an RPi not require clean power compared to other devices?
Cut-Throat
A PI as any other computer appreciates rock solid and clean supplies.The PI onboard supply is all but a high quality PS/regulator implementation.
Pair that with a mediocre external supply and you might see weird things happen. Especially if you start with things like overclocking, heavy DSP
work asf.
Beside that the PI 5V rail is offered to external devices such as HAT DACs or your HifiBerry (I've been running a HB DAC+ Pro of that 5V rail for some time).
In such as case the quality of 5V would have a direct impact on your DAC performance.
The same applies to USB BUS powered audio devices.IMO the quality of the PI supply does matter in many cases.
Edits: 10/04/16
I have been recently using RPi with MoOde Audio; quite an improvement over Volumio or piCore, IMO. I do use a choke LPS, BTW, and don't think "clean power" is the transformative thing for the Pi; improvement, yes, but still a way to go.. Through the Pi's USB out, the highs are awful i.e. fatiguing. I am playing wait-and-see with the Pi HAT boards; perhaps something will come along to make it a better listen. Certainly seems to be some interest and activity out there now.
I am using the Rpi Model 3 B...... I have a Hifi Berry Digi+ with Coax out. I don't use the USB. Also a Linear P.S. - I also run PiCoreplayer 3.02 -- I prefer LMS as I am using it throughout my network and House.Cut-Throat
Edits: 10/01/16
Did you get the transformer upgrade?
Yes, I actually have one of each! One I use with Optical (Non-Transformer) and the other with Coax (Transformer)
Cut-Throat
Give this a try it will give a further level of improvement.
Thanks Abe. Very good info.
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