Coburn
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Re: Coburns take on powering the Raspberry Pi via batteries

Wed Oct 19, 2011 4:03 am

Quote from emercer on October 19, 2011, 03:56
Sorry to sound spammy (I just posted a link to another Adafruit product in a different thread), but have you guys seen this inline battery charger? https://www.adafruit.com/products/280
I know the battery voltage is lower than what the RasPi uses, but can't we elevate it after the charger?

Ooh, I like that charger setup. I think it would be possible to do something like that, although we would need some bright spark to tell us how to do it. Since you would be charging 2 x 3.7V cells, that wouldn't be an issue... But the trick then would be trying to up the voltage to something that the Raspberry Pi would be able to use.

thassler
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Re: Coburns take on powering the Raspberry Pi via batteries

Wed Oct 19, 2011 6:51 pm

I was thinking on powering the Raspberry pi with something like that. I already saw the charger you mention but I was unable to find some technical details about that product. It is not specified if the charger is able to charge the battery and drain power from battery or power source while charging. I could not find anithing about max current that can be supplied from the battery while charging.
I have already bought this product: http://www.seeedstudio.com/dep.....?cPath=155 ,a solar panel and a battery.
That charger is able to charge the battery from USB, wall adaptor or solar panel while powering the Raspberry pi with a 5V regulated voltage. The only problem is that it only supply a max current of 350mA. If the Raspberry pi could be powered with 5V that would be just enough to drive the Raspberry pi without any peripheral. If the Raspberry pi needs more voltage a boost circuit would be needed and the final current supplied to the Raspberry would be very low.

The guys at that site are working in a new version of the charger that will supply about 1Amp so that would be a very good power supply for the Raspberry pi.

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emercer
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Re: Coburns take on powering the Raspberry Pi via batteries

Wed Oct 19, 2011 7:30 pm

from the Adafruit website
2 JST connections so you can keep the battery plugged in and powering your project

Yep, you can charge and use the battery at the same time. Also, according to the spec sheet, there is another IC for two serially-connected batteries (but no Adafruit charger based on it, we'd have to design another one around this one).

thassler
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Re: Coburns take on powering the Raspberry Pi via batteries

Wed Oct 19, 2011 7:54 pm

Sorry, you are right. I did not read that line.
What I do not understand is the charging current. Why should I want to change the charging current from 1.2A to 100mA? In order to protect the battery with slower charging? In order to charge a smaller capacity battery? or in order to give more current for the battery out?
Sorry if this is a stupid question but I am not an expert in electronics and I don´t know about lipo battery charging.
I am trying to understand why should I buy the Adafruit product instead of the cheaper Seeedstudio product I bought that also has a 5V regulation. I bought that charger to use it to power an Arduino robot but it does not provide enough current to drive servos so I am planning on using it for the Raspberry pi. In both cases I think the current would not be enough so I am looking for alternatives. For the robot, it would be enough to power the arduino but not the servos and in the case of raspberry pi, it would not be able to power usb peripherals.

Coburn
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Re: Coburns take on powering the Raspberry Pi via batteries

Wed Oct 19, 2011 10:48 pm

The charge current would switch from 1.2amps to 100ma to prevent overheating and such. If batteries get hot, they don't like being charged at a fast rate as you eventually will get an explosion. Like how some Windows phones prompt you with an error saying battery too hot if the battery can't be charged for some reason.

I looked for some 3.7V to 6V step up converters, but the ones I could find only supplied ~350ma. I suppose you could run the raspberry pi at 5V, it would be great if we can once they start shipping.

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emercer
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Re: Coburns take on powering the Raspberry Pi via batteries

Thu Oct 20, 2011 2:01 am

I believe the best bet would be building one around the sister-IC to the Adafruit uses, the one which supports two batteries serially... That would give us 7,4~8,4v output. Thankfully Adafruit give schematics to most of their projects (including the charger) so we can build one around their design.

Coburn
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Re: Coburns take on powering the Raspberry Pi via batteries

Thu Oct 20, 2011 10:22 pm

Well, the moment of truth. The raspberry Pi runs from USB 5V. That's good, because one can use a MicroUSB plugged into a 5000mAh USB Power Brick (eBay has them) to run their Raspberry Pi. And they even have LEDs to show how much juice is available.

tech guru
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Re: Coburns take on powering the Raspberry Pi via batteries

Sat Nov 26, 2011 6:59 pm

how about this its 11000mAh External Battery Pack and Charger (says it was designed for i pad) but it has a usb connector so all you need is a usb to micro usb cable and you would have plenty of power

http://www.amazon.com/New-Tren.....038;sr=1-3

(Key features includes
-With the ground breaking capacity of 11000mAh at 5V output voltage, this tiny device can get you an extra 50 hours of iPhone 4 ipod touch movie time and 17 hours ipad 2 movie time. It is stylish and powerful!)

Kenrik
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Re: Coburns take on powering the Raspberry Pi via batteries

Tue Nov 29, 2011 9:42 pm

It has a USB Power connector correct?

I use these Chinese li-ion batteries from ebay to power my video/photo equipment (LED Lights, ETC)

http://www.ebay.com/itm/12V-DC.....075wt_1008

They can recharge an iPhone 4 several times before they run out and since an iPhone consumes a LOT more power than the Pi I can see that these could last for quite some time.


RITRedbeard
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Re: Coburns take on powering the Raspberry Pi via batteries

Wed Nov 30, 2011 3:32 am

Yeah, you would probably have to get a lithium polymer battery in slightly higher voltage than you are expecting. Typically lithium polymer batteries come in 3.7v, 7.4v, 11.1v, 14.8v... the only reason to go NiMH is initial cost and safety. I believe you can get a 10.7vdc configuration in NiMH.

The real trick here will be having an inline charger similar to laptops and cellular telephones that can charge 9 cell batteries (typical for lappy battery) and be safe. If you could use the same pinout as the common laptop battery (with charging hardware), then you'd be pretty set.

Any electrical engineers? :D

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abishur
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Re: Coburns take on powering the Raspberry Pi via batteries

Wed Nov 30, 2011 1:12 pm

Considering the low power requirements of the r-pi I was just going to use 4 NiMH AA with a voltage boost to get it up to 5v. Then use the Maxim DS2715 to control the charging and power of the whole thing. If I really wanted to go crazy, I was going to use 8 NiMH AAs with two groups of 4 batteries wired in series to double the available amount of mAh.

All that said, there are equally easy solutions for Lithium batteries. They're just not quiet as forgiving as NiMH batteries.
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Nobody
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Re: Coburns take on powering the Raspberry Pi via batteries

Wed Nov 30, 2011 1:34 pm

You might want to be careful with the boost, as 4 fully charged rechargeable batteries can produce voltages in excess of 4*1.35 V = 5.4 V. Personally I might try to use 8 cells and a step-down/buck converter (e.g. the LM2675). Alternatively a low drop 5V regulator (e.g. LM2940) might also be an option for 5 or 6 cells - it would cost less than a dollar, but you would have to charge the cells externally.

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abishur
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Re: Coburns take on powering the Raspberry Pi via batteries

Wed Nov 30, 2011 2:46 pm

You can make sure just to get a voltage boost with a fixed output.

Edit: It's exactly how those mobile boost devices work. You slap two AA batteries in the holder, plug it into the mini-usb port and it boosts the 2.4-3v up to a fixed 5v output. Perfectly safe and reliable... well as perfectly safe and reliable as any electronic device can be perfect
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carf
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Re: Coburns take on powering the Raspberry Pi via batteries

Fri Dec 16, 2011 11:33 am

I think lobsrosity may have posted a similar item, but would this work?

http://www.amazon.co.uk/TeckNe.....38;sr=1-12

I'm not too sure what connection is needed for the Pi, or what Volt/watt (no idea which) would be needed/be too high for the pi. But this is only around £20 and with 7000mAh, which seems like it could power the Pi for some time?

Edit:

http://www.amazon.co.uk/New-Tr.....38;sr=1-14

This item is £36 but has 11000mAh and also says it outputs 5V (don't know if that is good enough or not...)

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crundy
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Re: Coburns take on powering the Raspberry Pi via batteries

Fri Dec 16, 2011 11:38 am

Quote from carf on December 16, 2011, 11:33
I think lobsrosity may have posted a similar item, but would this work?

http://www.amazon.co.uk/TeckNe.....38;sr=1-12

I'm not too sure what connection is needed for the Pi, or what Volt/watt (no idea which) would be needed/be too high for the pi. But this is only around £20 and with 7000mAh, which seems like it could power the Pi for some time?

Edit:

http://www.amazon.co.uk/New-Tr.....38;sr=1-14

This item is £36 but has 11000mAh and also says it outputs 5V (don't know if that is good enough or not...)

The first says it outputs 5v/1A as well (see the last picture)

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jojopi
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Re: Coburns take on powering the Raspberry Pi via batteries

Fri Dec 16, 2011 12:16 pm

Quote from abishur on November 30, 2011, 14:46
You can make sure just to get a voltage boost with a fixed output.


But what actual boost converter are you proposing to use, and what does its datasheet say about input voltages greater than its fixed output? How does efficiency suffer in that case, if it is even allowed?

You should start with more cells and buck, or with fewer and boost. It makes no sense to choose an input voltage range that requires a more expensive buck-boost arrangement.

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abishur
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Re: Coburns take on powering the Raspberry Pi via batteries

Fri Dec 16, 2011 1:21 pm

I'm not picky at all. I'd be fine with using the same total number of batteries but wiring them in groups of 2 such that the available voltage was in the 2.4-3v range but the total capacity doubled if that got me a bigger bang for the buck. ;)
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willlim
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Re: Coburns take on powering the Raspberry Pi via batteries

Fri Dec 16, 2011 1:58 pm

I have one of this http://www.dealextreme.com/p/s.....lack-57738
The output is 800ma and the solar panel 0.8W, i use for some arduino projects, should this be enough?at least for tests?i not intend in use R-pi at full capacity when using this charger.
or 1 of this http://www.dealextreme.com/p/s.....iver-59740 with more power

mexicodirk2
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Re: Coburns take on powering the Raspberry Pi via batteries

Fri Dec 07, 2012 7:01 am

HI

i use the Anker® Astro3 10000mAh Batterie and i am Happy! running without problems. And You can connect other devices like a little Monitor to 12V or something additional to the 2. USB 5V outlet! Also i can charge the Battery using the outlets for powering the devices in the same time.
Its a little bit expensive, o.k. you can buy 4 x 3000mAh batteries with Charger for 9.99 to 40.00 usd!
Li-Ion Battery have 3.7V you need 2 and you have 7.4 V , i think too much for the PI .
Normal Alkaline 1.5V you need 4 6V ok for PI, and the Trash Mounten grows up!
NiMH Batteris have 1.2V you need 5 for 6V ! The most Charger charging only 4 !
Your Charger never will stop running !
or the Bio Battery http://en.wikipedia.org/wiki/Lemon_battery :mrgreen: :mrgreen: :mrgreen:
you need a sack full Lemons :mrgreen: :mrgreen: :mrgreen:

Dirk

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