kevin56789
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Week-long, portable, power source?!?!?!?

Sat Jun 13, 2015 3:15 pm

I am currently working on an outdoor project that limits me from access to a stable power supply. I need to figure out a way to power my Raspberry Pi, which also has 2 camera add-ons and potentially the wifi adaptor. I found out something called PiJuice, which is a startup that creates portable battery for the Pi, but only for 24 hours. I don't think if that is realistic for my project cause it means that I have to go everyday to switch out the battery.

Has anyone encounter a similar problem before and have solved it? Or what did you try?

Thanks in advance!!!

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mahjongg
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Re: Week-long, portable, power source?!?!?!?

Sat Jun 13, 2015 3:28 pm

12v car battery!

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davidcoton
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Re: Week-long, portable, power source?!?!?!?

Sat Jun 13, 2015 4:13 pm

mahjongg wrote:12v car battery!
With, of course, a 12V to 5V converter! :shock: :roll: :ugeek:
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mahjongg
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Re: Week-long, portable, power source?!?!?!?

Sat Jun 13, 2015 4:37 pm

obviously! :roll:

hampi
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Re: Week-long, portable, power source?!?!?!?

Sat Jun 13, 2015 4:38 pm

Lead acid battery with a small solar panel is quite robust, safe and not too expensive system. For example like this

https://github.com/oh7bf/RaspiPwr12V/wi ... spberry-Pi

W. H. Heydt
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Re: Week-long, portable, power source?!?!?!?

Sat Jun 13, 2015 4:59 pm

Definitely with the solar charger. Otherwise you'd need a battery with something on the order of 80Ah capacity to run for a week.

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mikronauts
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Re: Week-long, portable, power source?!?!?!?

Sat Jun 13, 2015 5:07 pm

The OP never posted everything that would be hooked up to the Pi.

Assuming 1A @ 5V (low power WiFi, no monitor, no keyboard) that is a 5W draw

That's 120Whr per day, times seven days, 840Whr for a week.

Let's assume 90% efficient dc-dc converter, 840Whr * 1.1 = 924Whr

Using a 12V battery, that means 924/12 = 77Ahr, so W. H. Heydt is spot on!

If the draw is 50% more (ie Pi + peripherals = 1.5A @ 5V) then 115.5Ahr @ 12V is needed.
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MarkTF
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Re: Week-long, portable, power source?!?!?!?

Sat Jun 13, 2015 7:37 pm

That's 120Whr per day, times seven days, 840Whr for a week.
So a 60 kWh Tesla Model S would power a Pi for over a year and it meets the "portable" spec by virtue of being self-propelled. :lol:

Seriously though, there exist marine deep discharge batteries available in the 100+ Ah range, but that's a lot of battery and they aren't cheap.

Without knowing the specifics of the application, I wonder if a commercial Android phone or tablet might not be a better starting point as they have better power management, particularly if you don't need continuous operation. That is, if you want the sensor to wake up periodically, take a picture and then go back to a low power standby mode, you can get by with a lot less power. The downside it that the learning curve to programming such a device is much higher.

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Re: Week-long, portable, power source?!?!?!?

Sun Jun 14, 2015 3:44 am

mikronauts wrote:The OP never posted everything that would be hooked up to the Pi.

Assuming 1A @ 5V (low power WiFi, no monitor, no keyboard) that is a 5W draw

That's 120Whr per day, times seven days, 840Whr for a week.

Let's assume 90% efficient dc-dc converter, 840Whr * 1.1 = 924Whr

Using a 12V battery, that means 924/12 = 77Ahr, so W. H. Heydt is spot on!

If the draw is 50% more (ie Pi + peripherals = 1.5A @ 5V) then 115.5Ahr @ 12V is needed.
Thank you for doing the hard work. I used an approximation that [email protected] is roughly [email protected], allowing for conversion losses. Since a week is 168 hours, that would be 84Ah, or (rounding) about 80Ah.

Nice to know that an offf-the-top-of-the-head approximation came out that close.

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