Let's Make Robots!

Pi Power -- How I Made a Battery Powered USB Hub

Provides power to Raspberry Peripherals beyond 700ma

As I prepare to start adding peripherals to my Pi Bot, I wanted to be sure to get around the 700ma power budget the Pi has.  After searching for a cheap battery powered USB hub and finding little, I decided to hack up a few cheap(ish) parts and make my own.

1. USB Hub: $1.39

2. 5000mAh Battery: $17.93

3. DC-DC Converter: $2.76

Total: $22.08

 

 

 

 

 

The Battery Hack:

1. Crack it open.

2. Find POWER and GND.

3. Wire it up.

4. Make a small hole for wires and bring wires out.

5. Solder the respective leads to the DC-DC converter.

6. Smile, then sit through my way too long of a video to make it into the HUB.

 

Hope all are well. :)

 

NOTE: Regarding the error at the end of the video.  Don't panic (that's what I did).  I actually found out this had nothing to do with my hub, it had to do with plugging an iPhone into a Raspberry Pi.

NOTE2: I realize I used the wrong "hearty," my brain has problems typing homonyms and parahomonyms. :P

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usually the GND should be common when connecting different circuits with separate supply, which is not the case in the hub shown in the video

 

It's because that battery has a boost circuit that outputs 5.5v, not 5v. Raspberry Pi should be between 4.75-5.25v. Although, now that you mention it, I probably should have hacked in directly at the battery. Sorry for such long video :( http://www.raspberrypi.org/archives/260

Well, actually my unit (at least) there's 5.2V branded on the chassis... however since you've told it wasn't 5V that it output (a few days ago) I took my multimeter to it... and actually read about 5.02V everytime I tried (I tried at least 3 times in three different ocassions being one of them right now :P).

I would say, that if 5.2V was what they were really aiming at, both of us got thrown 0.2-0.3V in opposite directions "off-center" :P

Ah... I was about to tell you that wasn't actually a powered usb hub... but then I saw the video, well skimmed through it :P And yeah... it actually is (probably it would be best to add another final photo with the whole final setup).

 

However there's one thing still intriguing me... the battery bank uses a 1S LiPo battery, thus you get nominal 3.7V ... which are stepped up to 5V by that circuit.... you've seem to have "fished" the power lines after stepping up... and yet your re-directing them to yet another step up DC-DC converter... and getting 5V ... I'm confused (more to say pending reply).

See above. (Stupid iDevice.)

That's what you get for buying Apple :P but at least you're fashionable, right? :P

Oh btw, the other day (given that my unit seems to output 5V) I actually hacked a usb cable to connect to a power distribution board (basically a perf with lots of parallel male pins) but as it seems my rpi was reseting so I guess that solar thinguie by itself can't deliver enough current for all my setup :| hopefully the 20Ah unit will... for now I use the solar + rc 2s lipo combo :P

My wife won it :) Not a fan of Foxconn. I should ask OddBot if the stories about them are true. Hmm, not sure on the 5v mystery, but "5.5v" is what's marked on the back of mine...and you know how I feel about frying my Pi. :) Mmmm....fried pie. I assume your limitation is the current output of the built in boost circuit? What's the current provided on your 20aH?

Well, I haven't measure it, but my current solar one is rated (markings at the back) at 1500mA output... so I guess something under that value :P

whereas the 20Ah has two outputs, one rated at 1A and another rated at 2.1A... so let us wait and see how much near to reality that is :P