Sentinelace
Posts: 36
Joined: Sun Sep 29, 2013 12:51 am

Battery Power a Pi with Camera?

Sat Oct 03, 2015 9:11 pm

I am running Motion Pie which is working great. However where I want to location the pi has no outlet. Is i possible to get battery power to the pi that can last a month? or couple weeks?

Higgs
Posts: 43
Joined: Tue May 26, 2015 2:17 pm

Re: Battery Power a Pi with Camera?

Sat Oct 03, 2015 9:43 pm

For anything to run long on a battery it would have to put the RPi to sleep when not used for it's purpose (like no movement detected).

http://spellfoundry.com/sleepy-pi/sleepy-pi-faq/

However, you can see that this approach then requires the Pi to boot-up again, which can take 25-30 secs with a standard Raspbian image - which means your subject could be long gone by then.

I tried once (just for the heck of it) hot-wiring an ATTiny chip to a motion sensor and a cheap keychain camera (with micro-SD storage) to make it take either a sequence of pictures or some limited-time video clips when the sensor detected motion (it was more sensitive than the motion detection built into the camera). The time to wake up the ATTiny and power-on the camera to start taking vid was about 12 secs (mostly waiting for the cheap camera to start taking vid - it required press/hold a few secs of a button to signal the camera to start recording, which was automated via the ATTIny). The sensor drew <50ua waiting to trigger the sleeping ATTiny.

CORRECTION: It took about 6 secs to start taking vid. 12 secs was the time gap between the end of a vid, powering down, and then immediately powering up again to take another vid.

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Burngate
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Re: Battery Power a Pi with Camera?

Sun Oct 04, 2015 9:36 am

Rough figures:
The Pi takes 1A (maybe less, but that makes the arithmatic easy) at 5v, so 5W
With 24 hours in a day, 7 days in a week, and 4 weeks in a month, that's 700 hours (ok, 672, but some months have more than 4 weeks)
So 3500 Watt-hours.

A quick look on EuroCarParts tells me my Volvo uses a 73 AH battery. Rounding that to 70, and assuming 10v rather than 12v, gives 700 watt-hours.
So five of those would run a Pi for a month. Probably.

Sentinelace
Posts: 36
Joined: Sun Sep 29, 2013 12:51 am

Re: Battery Power a Pi with Camera?

Sun Oct 04, 2015 4:03 pm

well crap. I"ll have to get an outlet then

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