Saturday, September 15, 2012


Meet the SolarPi!

...look inside...

There is a raspberry pi in there, under the tray. Note the red key, that's a safety feature, cause this is not a toy. I reckon that I could probably run it a whole week non stop purely on batteries.

I built this a few years ago, from a toolbox on wheels.

I'm using sealed lead acid batteries (7 x 12v currently for 49Ah capacity, but 12 x 12v 7Ah for 84Ah total capacity, at some point in the past), lots of wires.

The wires are connected together with 2 rails with screws to have a common parallel connection. These are typically used for ground buses for fuse boxes. Negative side:

Positive side:

Safety first, there is a key to close the circuit. Amp meter is always on, while the voltmeter engages with the switch in the middle pulled. Yeah, I know 50 amps is crazy for the Pi, considering is pulls about 4.2 watts (less than half an ampere at 12V) without wifi or 6.8 (just a tad over half an ampere) with wifi active and transmitting. But I've designed this initially to use with a 110V power inverter too and camping gear, and it's easy to pull 30 amps + with those...

And the reason I thought about sharing this project today: the solar panel.

I have 2 of those, and I use them also to charge my electric bicycle batteries. I connect them to the battery through a solar panel controller that regulates the voltage so that I don't fry the batteries.

Why am I sharing this story today?

What happened is that I met Mike today, in the parking lot of a commercial shopping center, in Winston Salem, North Carolina. He builds electric vehicles. This one is a chEVrolet :)

144V was true some months back, he now runs a bit higher voltage using Lithium batteries with a bunch of BMS (battery monitors). He swapped the previous battery pack out (over 1000lbs, 18 batteries at 8V each, lead acid) but didn't repaint the truck :)

There is quite a bit more information on his truck here at: Backyard Green. So we talked a good bit about the tech, and even got into the subject of solar power, and I mentioned I powered one of my raspberry pi through solar power. I thought that maybe others would be interested in this aspect, the "green computing" side of the pi...

Anyway, back to Mike, he does a good bit of work with microcontrollers and he had a pi lookalike embedded in the console of his electric truck and he's thinking of building his own graphical interface. Sounds like a perfect match for the Raspberry Pi and Python... At any rate, it was a really interesting discussion.


Francois Dion said...

Fixed the picture sizes. Sorry about that, was particularly painful on the iPhone...

Stuart Clark said...

Hii your blog is look so nice and the content is also very informative for me. Thanks to share all of these things with us. I am waiting for your new one please continue it.
Lithium battery pack

Annie Khan said...

I must say that you are a great blogger and really described well for solar power projects.... Solar Panel