zekeb
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Re: Potential power source

Mon Mar 19, 2012 6:11 pm

Could this be used to power the R-Pi?

http://www.rndpowersolutions.c....._p_83.html

The voltage is correct, but the current capacity (2000mA) far exceeds the 700mA cited in the FAQ.

The nice thing about this is that it provides 8000mA - which should triple the battery life of most portable cell phone charging devices.

Joe Schmoe
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Re: Potential power source

Mon Mar 19, 2012 6:32 pm

The extra current capacity is not a drawback; in fact, it is a bonus.  The device will only draw what it needs.

Looks interesting to me - of course, it costs more than the Pi itself, but then again...  I wonder how much it weighs (I couldn't tell that from the site)
And some folks need to stop being fanboys and see the forest behind the trees.

(One of the best lines I've seen on this board lately)

robleady
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Re: Potential power source

Mon Mar 19, 2012 6:36 pm

Yes, it should be able to...  although that device doesn't appear to actually include a charger.  You still need something to charge its batteries before it can be used to power anything else.

Just because a power source is capable of delivering 2000mA, that doesn't make a device connected to it draw that much current...

Cheers,

Rob

poing
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Re: Potential power source

Mon Mar 19, 2012 6:42 pm

According to Amazon shipping weight is 12 ounces / 340 grams. So maybe 300 grams for the battery?

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alexeames
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Re: Potential power source

Mon Mar 19, 2012 6:42 pm

Looks more suited to apples than raspberries to me.

It's just a lipo in a case with USB ports and a regulator. (Maybe some charge circuitry too?) I'm sure it will do the job, but you don't need to spend anything like that much money to power your Pi.
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chipmonger
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Re: Potential power source

Mon Mar 19, 2012 7:18 pm

I'd use one of these myself... http://www.geekstuff4u.com/80-.....board.html

Joe Schmoe
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Re: Potential power source

Mon Mar 19, 2012 7:30 pm

Funny...
And some folks need to stop being fanboys and see the forest behind the trees.

(One of the best lines I've seen on this board lately)

zekeb
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Re: Potential power source

Mon Mar 19, 2012 7:47 pm

Excellent…Among the many uses I have planned for mine is an ultra portable replacement for my laptop for travel and work presentations.

I plan to use a vanilla phone style charger to power it when I am close to an outlet (I think you call them powerpoints in the UK – I wonder if MS has to pay royalties for the name?), but pairing this with a pico projector and foldable mouse/keyboard would provide a portable that is comparable in price to a netbook that would fit in my pocket(s)

Also with the large capacity, I think I can triple the 3 hour lifespan others have estimated using a 2300mAh charger.

I wonder if I could distribute the power with a little hub to the projector or an external HDD?

Phil Spiegel
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Re: Potential power source

Mon Mar 19, 2012 9:48 pm

An increased current-capacity on the charger won't, in itself, increase the duration of operation of the Pi from a battery; however, it would allow you to charge a larger-capacity of battery at optimum rate, in the 'same time'; which in-turn, would allow the Pi to run longer on the related battery once charging was completed.

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alexeames
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Re: Potential power source

Mon Mar 19, 2012 10:05 pm

There's a bit of terminological confusion in the OP. The "charger" is in fact a battery, with circuitry and sockets, which itself charges other devices. If I have it right, zekeb wants to use the device itself to power the Pi for portable use. (ie use the battery as a battery, which should work fine.) The other thing is, he's referred to 8000 mA instead of mAh.

As far as I can make out, the "charger" is a single cell 8000 mAh lipo, which probably steps up to 5.0V output (which means it's going to be able to deliver a bit less than 8000 mAh at 5V - but it will still fit the bill, I think). The product page doesn't state the weight, from which it might be possible to guesstimate the cell count more accurately.
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tzj
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Re: Potential power source

Mon Mar 19, 2012 10:19 pm

@ zekeb they are called sockets, just to let you know

$200+ for 80 usb ports, sounds a bit expensive.
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Vindicator
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Re: Potential power source

Tue Mar 20, 2012 2:00 am

Does anyone here have 80 devices they need to charge at once, and if you do the least of your problems is a $200 80 port USB (LOL)especially since all it can do is charge.
If you are more worried about ,spelling, punctuation or grammar you have probably already missed the point so please just move on.

semtex
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Re: Potential power source

Tue Mar 20, 2012 6:34 am


I plan to use a vanilla phone style charger to power it but pairing this with a pico projector and foldable mouse/keyboard would provide a portable that is comparable in price to a netbook that would fit in my pocket(s)


Brilliant idea! I like that a lot

hzrnbgy
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Re: Potential power source

Tue Mar 20, 2012 1:40 pm

if you fancy a bit of soldering, here are some good switchmode power supplies

http://www.mouser.com/Power/Pl.....k=P_MarCom

billio
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Re: Potential power source

Tue Mar 20, 2012 1:54 pm

hzrnbgy said:


if you fancy a bit of soldering, here are some good switchmode power supplies


Is it practical to use switched mode power supplies from old PCs ?. The one I have, which must be at least 10 years old, supplies 5 volts at up to 28 amps, plus 12volts and 8 amps  and 3.3 outputs. The is a bit over the top for one RPi but it costs nothing.

Chris.Rowland
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Re: Potential power source

Tue Mar 20, 2012 2:04 pm

I use an old PC power supply to drive things and it seems to work well.  You may need to short a couple of connections to get it to turn on and some people say that the 5V line has to draw a significant amount of current before it regulates.

I think you need some electronic experience to do this, it will be worth checking that the voltage is at least reasonable before risking a Pi

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Re: Potential power source

Tue Mar 20, 2012 2:24 pm

billio said:


hzrnbgy said:


if you fancy a bit of soldering, here are some good switchmode power supplies


Is it practical to use switched mode power supplies from old PCs ?. The one I have, which must be at least 10 years old, supplies 5 volts at up to 28 amps, plus 12volts and 8 amps  and 3.3 outputs. The is a bit over the top for one RPi but it costs nothing.



Yes it's possible and quite easy to do, but it's overkill and you will have fan noise, thus negating a major advantage of the Pi. Most PC power supplies are 200+ watts. Don't really need such welly with a 2 watt device. But it will work.
Alex Eames RasPi.TV, RasP.iO

zekeb
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Re: Potential power source

Tue Mar 20, 2012 3:36 pm

alexeames said:


There's a bit of terminological confusion in the OP. The "charger" is in fact a battery, with circuitry and sockets, which itself charges other devices. If I have it right, zekeb wants to use the device itself to power the Pi for portable use. (ie use the battery as a battery, which should work fine.) The other thing is, he's referred to 8000 mA instead of mAh.


Correct - typo in my original post - device provides 2000mA at 8000mAh

And, yes I want to use this as a battery, not as a charger. I will use a charger to recharge the battery or power the pi on a desktop at the hotel.

Also, thought you might be interested in the specs I got from the manufacturer:

Dimensions: 4.25 X 3 X .75 InchesWeight: 7.6 Ounces.

So it is lighter than we suspected (by about 75g), and certainly smaller than the picoprojector I have in mind. 

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alexeames
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Re: Potential power source

Tue Mar 20, 2012 4:00 pm

Must be a single cell at that weight. But you can get almost any voltage from any other with DC-DC convertors these days. Should be plenty of capacity there to run your Pi for several hours at full power.
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W. H. Heydt
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Re: Potential power source

Tue Mar 20, 2012 6:26 pm

alexeames said:


billio said:


hzrnbgy said:


if you fancy a bit of soldering, here are some good switchmode power supplies


Is it practical to use switched mode power supplies from old PCs ?. The one I have, which must be at least 10 years old, supplies 5 volts at up to 28 amps, plus 12volts and 8 amps  and 3.3 outputs. The is a bit over the top for one RPi but it costs nothing.


Yes it's possible and quite easy to do, but it's overkill and you will have fan noise, thus negating a major advantage of the Pi. Most PC power supplies are 200+ watts. Don't really need such welly with a 2 watt device. But it will work.



Well...  for some values of "modern."  On the other hand, if you go back to the original IBM PC, the power supply was rated at 63.5 W. (Still overkill, but a long ways from modern 1+ KW supplies.)

ajwillys
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Re: Potential power source

Tue Mar 20, 2012 8:07 pm

I'd like to use a "bare" Li-ion battery pack like this:

https://www.adafruit.com/products/354

It seems like it would be relatively easy to solder this inline (somewhere) but I don't have the abilities to know where and what the gotcha's are.  It would also be nice if I could still charge this battery pack using microusb (built-in or otherwise).

Is this a simple thing?

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Re: Potential power source

Tue Mar 20, 2012 8:57 pm

I think a few of these in parallell might be a go-er


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alexeames
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Re: Potential power source

Tue Mar 20, 2012 9:31 pm

ajwillys said:


I'd like to use a "bare" Li-ion battery pack like this:

https://www.adafruit.com/products/354

It seems like it would be relatively easy to solder this inline (somewhere) but I don't have the abilities to know where and what the gotcha's are.  It would also be nice if I could still charge this battery pack using microusb (built-in or otherwise).

Is this a simple thing?



The gotchas are in the charging. Lipos are charged at constant current for phase 1 of the charge until they reach ~4.15 volts/cell (usually at 1C or less - so a 4000 mAh pack would be 4A or less - although there are now batteries that can be charged faster, they are heavier) and then constant voltage (~4.1-4.2 v/cell) with decaying current until current is about C/100. You will need to incorporate some electronics to achieve this - or simply detach the pack and use a dedicated lipo charger and learn how to care for them.

The other gotcha is in the discharging. If you discharge right down to 3.7 V/cell (resting voltage) or below, you will shorten the life of your batteries. So you'll need some circuitry for that too (a warning buzzer or a cutoff).

Ignoring these can be dangerous as these cells will go bang if abused. Mobile phones etc. all have this stuff built in, and even then, occasionally you hear about one going pop in someone's pocket. I don't know where to get the circuitry from, as I have lipo chargers and stuff already from my electric RC planes. But I'm sure it is not hard to make or obtain.
Alex Eames RasPi.TV, RasP.iO

timn
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Re: Potential power source

Tue Mar 20, 2012 10:59 pm

+1 on Alex's posts.

If you are interested in using Lipo batteries then I suggest you search for 'lipo fire' on Youtube to see what happens when they are not correctly looked after. I keep mine outdoors.

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alexeames
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Re: Potential power source

Wed Mar 21, 2012 9:36 am

timn said:


+1 on Alex"s posts.

If you are interested in using Lipo batteries then I suggest you search for "lipo fire" on Youtube to see what happens when they are not correctly looked after. I keep mine outdoors.


There"s a list of incidents somewhere in the battery section of rcgroups.com. Almost all incidents happened during charging, usually due to user error, but there were one or two "spontaneous". Just enough to leave a doubt in the mind. I keep mine (at 50% charge for longevity) in an ammo box in the garage, when not in use.
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