Best power source for RPi for these needs

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rahatmaini
 
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Best power source for RPi for these needs

Post by rahatmaini »

I'm in need for a portable power supply for the RPi, but I only want to buy everything I need from Adafruit. So far, I know that I will be using the Model A, with a simple USB port hub that will probably only have the super small USB wifi adapter you sell in store, and maybe a Bluetooth module (the small one you sell again in store). That's it, WiFi and Bluetooth and Pi. It can be any battery, lithium or just regular alkaline ones. I just need a relatively small power source that lasts maybe 30 mins.

Thanks so much!

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Franklin97355
 
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Re: Best power source for RPi for these needs

Post by Franklin97355 »

Small and powerful equate to LiPo batteries
http://www.adafruit.com/products/962
http://www.adafruit.com/products/353
would be good starting places.

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rahatmaini
 
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Re: Best power source for RPi for these needs

Post by rahatmaini »

Do you have an estimate of how many amps the Model A plus a hub with the small WiFi adpater will use? Also, the last option is 3.7v, RPi needs 5V I think.

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adafruit_support_mike
 
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Re: Best power source for RPi for these needs

Post by adafruit_support_mike »

PID 962 is your best choice..

The RasPi offers an interesting combination of challenges when it comes to battery power. It demands 5v @ 700mA, which is exactly the wrong value for anything involving LiPos (their nominal voltage is 3.7v.. about 3/4 of what the RasPi needs). Normally you can put two batteries in series to get more voltage, but the RasPi doesn't have a voltage regulator, so two LiPos in series will kill it.

So.. making the RasPi work with LiPos means you need a DC-DC voltage converter. Those are subtle and complicated circuits (there are whitepapers written by engineers from the major component manufacturers with titles like: "switching regulators.. how to make the damthings work" and "switching regulators without (too much) pain").

Ladyada demonstrated her EE-jitsu when she designed the MintyBoost, but that one is tuned to produce 500mA.. not enough for a RasPi (and it runs from AA batteries instead of LiPos).

PID 962 is roughly equivalent to the MintyBoost running on LiPos, with the current hiked up to 1A. The circuit you'd build yourself would do exactly the same thing, and would use specially-made driver chips to handle most of the magic anyway. Unless you have that special flavor of masochism that drives people to become switching regulator designers, it's easier to buy the functionality in a box with a switch and a plug, then get on with your preferred mania. ;-)

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