Garacesh
Posts: 17
Joined: Wed Jan 25, 2012 12:16 pm

Re: Rechargeble batteries suitable for the RPi?

Wed Jan 25, 2012 5:00 pm

Currently I have a MicroUSB chargeable MP3 player, that I'm thinking of ripping the battery out of and hooking up to the RasPi, but admittedly I don't know what voltage it runs on or any of that lark, which brings me to my actual question: Whacking a rechargeable battery into the Pi.

Now it's powered by 5v MicroUSB, I get that. So the question is, does anybody know of any compatable batteries that can either: be soldered/hooked up in some way to the RPi to supply power and can be recharged (preferably by USB without removing it, as I'd rather have the battery fixed inside the case and connected up), so basically powered in the same fashion as MP3 players, mobile phones and other devices of the like. Simultaneous charge-and-use would be a bonus, but is admittedly not essential.

(If anybody is wondering, I'm working with the totally-original idea of turning an RPi into some form of PD)

kasperl
Posts: 90
Joined: Fri Jan 06, 2012 6:20 pm

Re: Rechargeble batteries suitable for the RPi?

Wed Jan 25, 2012 5:18 pm

I've seen this: http://www.sparkfun.com/products/8483 linked somewhere else here. Combined with this: http://www.sparkfun.com/products/10300 it'll run a bare Pi for about 2 hours, I'd guess.

(3.7V at 2000mAh, makes for 7.4 Wh, 600mA at 5V makes for 3W, so a bit over 2 hours ideally. Not counting peripherals.) I'll let a real sparky explain how to run more than one of those to the same Pi, or how to allow more current to be drawn.

kasperl
Posts: 90
Joined: Fri Jan 06, 2012 6:20 pm

Re: Rechargeble batteries suitable for the RPi?

Wed Jan 25, 2012 5:18 pm

I've seen this: http://www.sparkfun.com/products/8483 linked somewhere else here. Combined with this: http://www.sparkfun.com/products/10300 it'll run a bare Pi for about 2 hours, I'd guess.

(3.7V at 2000mAh, makes for 7.4 Wh, 600mA at 5V makes for 3W, so a bit over 2 hours ideally. Not counting peripherals.) I'll let a real sparky explain how to run more than one of those to the same Pi, or how to allow more current to be drawn.

Garacesh
Posts: 17
Joined: Wed Jan 25, 2012 12:16 pm

Re: Rechargeble batteries suitable for the RPi?

Wed Jan 25, 2012 5:24 pm

Actually, I was looking at that very same battery earlier today, but didn't see the charger/booster and thus was unsure if it would have been any good.. I shall keep it in mind.

rmw00
Posts: 4
Joined: Fri Jan 20, 2012 3:57 pm

Re: Rechargeble batteries suitable for the RPi?

Wed Jan 25, 2012 5:39 pm

I'd be very surprised if the board won't run on 3.7V. I've powered several USB (5V) devices with a single lithium cell.  Typically the 5V goes first to a 3.3V regulator, then on the the chips.  Put in 3.7V and it gets regulated to 3.3V.  I'm guessing most of the components here are for the mobile device industry and are designed to run on a regulated single Li cell.

If so, use a LiIon of LiPo.  2000mah at 800ma (what I heard the board uses) is just over 2 hours.  I like http://www.all-battery.com/index.aspx  They have LiIon up to 2600mah and LiPo up to 50Ah(!).  I used one of these 10000mah cells once: http://www.all-battery.com/pol.....30104.aspx

You can put Lithium cells in parallel to get more capacity.  Don't put them in series unless you have a balance circuit in the pack.  Also, if you completely deplete a Lithium cell, it's probably ruined.  Use a protection circuit that cuts off the current before the cell dies.  Like this: http://www.all-battery.com/Pro.....32088.aspx

Maybe I should make a battery for the R-pi available for sale???

kasperl
Posts: 90
Joined: Fri Jan 06, 2012 6:20 pm

Re: Rechargeble batteries suitable for the RPi?

Wed Jan 25, 2012 5:43 pm

rmw00 said:


Is the current consumption of the board been published?



There's some info on the Wiki: http://elinux.org/RaspberryPiBoard in the hardware table. You're looking at 500mA (5V) for a A, 700mA for a B. Mind you, these figures are probably while running, and I've seen much lower numbers being thrown about for idle states. However, this all is without any peripherals, so no keyboard, no mouse, no USB stick, and nothing soldered on the GPIO drawing off the 5V or 3.3V pins.

Garacesh
Posts: 17
Joined: Wed Jan 25, 2012 12:16 pm

Re: Rechargeble batteries suitable for the RPi?

Wed Jan 25, 2012 6:00 pm

Kasperl said:


Database Error
Error establishing a database connection

What? No he didn't.. Lies!

Anyways.. You raise a valid point, good sir. Care to hazard a guess at the overall power usage once a touchscreen is slapped on?

I can build a desktop PC from scratch no problem, but this? Boggles the mind at times.. I admit I'm working in theory for now (but then again, until release, aren't we all?) I don't know much for electrical engineering but I'm still going to give this a damn good shot! xD


Garacesh
Posts: 17
Joined: Wed Jan 25, 2012 12:16 pm

Re: Rechargeble batteries suitable for the RPi?

Wed Jan 25, 2012 6:01 pm

Accidental double-post.. Mah bad..

drgeoff
Posts: 10938
Joined: Wed Jan 25, 2012 6:39 pm

Re: Rechargeble batteries suitable for the RPi?

Wed Jan 25, 2012 8:32 pm

1.  The specs for USB 2.0 say that a host socket should supply 5volts +/- 5%.  As far as I know there are no voltage converters on the RP board which can increase voltage.  Therefore the use of a single cell Lithium battery cannot guarantee that USB peripherals will work.

2.  Though the nominal voltage of a lithium cell may be quoted as 3.7, a fully charged one is typically around 4.2.  This is too high to be fed directly to any 3.3 volt circuits on the board.

3.  A lithium cell will be damaged if it is discharged too far.

In conclusion a lithium cell without surrounding electronics is not a good solution as a rechargeable battery for the RP.
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cowfodder
Posts: 12
Joined: Mon Jan 09, 2012 11:07 pm

Re: Rechargeble batteries suitable for the RPi?

Wed Jan 25, 2012 9:20 pm

drgeoff said:


1.  The specs for USB 2.0 say that a host socket should supply 5volts +/- 5%.  As far as I know there are no voltage converters on the RP board which can increase voltage.  Therefore the use of a single cell Lithium battery cannot guarantee that USB peripherals will work.

2.  Though the nominal voltage of a lithium cell may be quoted as 3.7, a fully charged one is typically around 4.2.  This is too high to be fed directly to any 3.3 volt circuits on the board.

3.  A lithium cell will be damaged if it is discharged too far.

In conclusion a lithium cell without surrounding electronics is not a good solution as a rechargeable battery for the RP.


While you are correct the fully depleting a lipo cell is back, running 2 3.7v protected cells in series through a voltage regulator to get it down to a steady 5v would be safe.  I am an ecig user, and all of my devices are 5v regulated down from 2 14500 3.7 batteries.

drgeoff
Posts: 10938
Joined: Wed Jan 25, 2012 6:39 pm

Re: Rechargeble batteries suitable for the RPi?

Wed Jan 25, 2012 11:28 pm

cowfodder said:


drgeoff said:


1.  The specs for USB 2.0 say that a host socket should supply 5volts +/- 5%.  As far as I know there are no voltage converters on the RP board which can increase voltage.  Therefore the use of a single cell Lithium battery cannot guarantee that USB peripherals will work.

2.  Though the nominal voltage of a lithium cell may be quoted as 3.7, a fully charged one is typically around 4.2.  This is too high to be fed directly to any 3.3 volt circuits on the board.

3.  A lithium cell will be damaged if it is discharged too far.

In conclusion a lithium cell without surrounding electronics is not a good solution as a rechargeable battery for the RP.


While you are correct the fully depleting a lipo cell is back, running 2 3.7v protected cells in series through a voltage regulator to get it down to a steady 5v would be safe.  I am an ecig user, and all of my devices are 5v regulated down from 2 14500 3.7 batteries.



Yes, but you know what you are doing.  I fear that the OP doesn't.  _  No offence meant to him but it needs to be said that lithium cells are dangerous if not used properly.  The larger packs such as in laptops contain sophisticated protection circuits but even so, think about how many recalls there have been of laptop batteries.  The small cells found in mobile phones, i-things etc tend to have minimal internal protection and rely on the host device to safeguard against overcharging and overdischarging.  Hence it isn't a good idea to use those cells in equipment that wasn't specifically designed to take them.
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Garacesh
Posts: 17
Joined: Wed Jan 25, 2012 12:16 pm

Re: Rechargeble batteries suitable for the RPi?

Thu Jan 26, 2012 10:20 am

You are correct good sir, I don't really know what I'm doing, hence why I'm asking for ze community help.

No offence taken, I assure you.

rmw00
Posts: 4
Joined: Fri Jan 20, 2012 3:57 pm

Re: Rechargeble batteries suitable for the RPi?

Thu Jan 26, 2012 11:09 am

Lithium cells are only dangerous if charged or discharged too fast.  If you cause a short circuit, there could be smoke etc.  Single cells generally don't need any protection for safety sake, only to prevent loss of capacity.  If you have several in series, then you need a balancing curcuit.

The voltage regulator on the board reduces the incoming 5V to 3.3V which is what the chips use - look them up!  The only reason we have 5V coming it is because that's the USB spec and USB power supplies are cheap and easy to get.

If you apply less than 5V, the regulator still drops the voltage on the board to 3.3V.  If you apply 4.2V, the chips still see 3.3V, if you apply 3.7V, the chips still see 3.3V.  Now if you apply 3.0V, the chips will see 3.0V minus a bit lost in the regulator.

So... If you have a proper Lithium charger and don't cause a short by connecting the plus to the minus (red wire to black wire for you software guys), there is no danger.  If you want the battery to last a long time, use a circuit to prevent discharging too deep.

I don't know which voltage regulator they are using, but any voltage from 5V to just over 3.3V should work fine.  The last regulator I used in a similar application was rated up to 12V input and this may be the same, but until we know, 5V max.  I'm currently designing an ARM based board and our regulator will take up to 12V.

drgeoff
Posts: 10938
Joined: Wed Jan 25, 2012 6:39 pm

Re: Rechargeble batteries suitable for the RPi?

Thu Jan 26, 2012 12:09 pm

I'm fairly certain the onboard 3.3 volt regulator is a cheap linear one and will need at least approximately 3.8 volts on its input before it starts regulating.

To answer the original question, I would suggest 4 AA or C NiMh cells in series giving around 4.4 to 5 volts which will be ample for the 3.3 volt regulator and will probably be OK for most USB devices.  Holders for these cells  are readily available eg http://www.maplin.co.uk/aa-siz.....ders-31427.

Or for guaranteed to work, put 6 in series and a 5 volt regulator.  Heat sink on the regulator advisable.

AA size gives around 2500 mAH. Chargers are readily available.

In emergencies when the NiMHs are flat and cannot be recharged, disposable alkalines can be substituted.
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tumblebomb
Posts: 50
Joined: Sun Nov 27, 2011 4:56 pm

Re: Rechargeble batteries suitable for the RPi?

Thu Jan 26, 2012 1:13 pm

I would quite fancy taking a laptop power pack, getting an appropriate charger and step-down circuit. It would certainly provide many hours of use but not very portable.

Garacesh
Posts: 17
Joined: Wed Jan 25, 2012 12:16 pm

Re: Rechargeble batteries suitable for the RPi?

Thu Jan 26, 2012 3:33 pm

drgeoff said:


*snip*

4 AA or C NiMh cells in series

*snip*

Or for guaranteed to work, put 6 in series and a 5 volt regulator.  Heat sink on the regulator advisable.

*moar snip*



Forgive my naivity, can a series of cells be recharged in-series, or would they need to be recharged separately? i.e. removing them from the Pi and plugging them into a typical mains charger? Or would I just be able to, say, plug a USB into the battery mount and introduce a current to the circuit that would charge them?

error404
Posts: 351
Joined: Wed Dec 21, 2011 11:49 pm

Re: Rechargeble batteries suitable for the RPi?

Thu Jan 26, 2012 6:19 pm

Garacesh said:


Forgive my naivity, can a series of cells be recharged in-series, or would they need to be recharged separately? i.e. removing them from the Pi and plugging them into a typical mains charger? Or would I just be able to, say, plug a USB into the battery mount and introduce a current to the circuit that would charge them?



Depends on the battery chemistry. It's pretty much always better to charge the cells separately if you can, but charging in series is often okay. However sometimes it can destroy cells because of imbalance (typically Li-Ion).

For NiMH it's generally okay, at least at low charge currents, and less bad with a small number of cells. If you were okay with a trickle charge (12h charge cycle), then you can just run a 0.1C constant current to the battery to charge it. It's pretty much okay to run this 24/7, though it will reduce the life of the battery somewhat. If you want fast charging you will need a more complex charge circuit; its probably still okay at a 4S pack to charge in series, but you will need a proper charge controller.

drgeoff
Posts: 10938
Joined: Wed Jan 25, 2012 6:39 pm

Re: Rechargeble batteries suitable for the RPi?

Thu Jan 26, 2012 6:37 pm

Garacesh said:


drgeoff said:


*snip*

4 AA or C NiMh cells in series

*snip*

Or for guaranteed to work, put 6 in series and a 5 volt regulator.  Heat sink on the regulator advisable.

*moar snip*



Forgive my naivity, can a series of cells be recharged in-series, or would they need to be recharged separately? i.e. removing them from the Pi and plugging them into a typical mains charger? Or would I just be able to, say, plug a USB into the battery mount and introduce a current to the circuit that would charge them?


Ideally, NiMh cells should be charged individually with an intelligent charger which monitors the voltage of each cell.  However a set of cells can be charged and discharged in series many, many times before they go seriously out of balance.  Remember those 6 volt NiCad battery packs for camcorders of 20 years ago - they had 5 cells in series with no possibility to access the individual cells.

5 volts is not really enough to charge 4 NiMh cells in series.  With a 2 pole 2 way switch it would be possible to rearrange them as 2 off 2 in series with two current limiting resistors for charging.  The circuit is very simple but this forum doesn't seem to have a facility for me to attach an image from my local PC.
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speedevil
Posts: 7
Joined: Tue Jan 24, 2012 3:27 am

Re: Rechargeble batteries suitable for the RPi?

Fri Jan 27, 2012 1:59 am

I suggest cheating.

http://www.dealextreme.com/p/5.....ters-91411

This has inside it 2*18650 lithium cells, and a power converter suitable to charge them from USB, and to provide a USB output.

I plan to measure the efficiency over the next several days.

You could in principle simply use this board with your own battery.

The power converter board looks well constructed.

Stock, it will run the Pi for around 7 hours.

Garacesh
Posts: 17
Joined: Wed Jan 25, 2012 12:16 pm

Re: Rechargeble batteries suitable for the RPi?

Wed Feb 01, 2012 12:07 pm

Any luck? How'd the efficiency tests go?

MrStipo
Posts: 8
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Contact: Website

Re: Rechargeble batteries suitable for the RPi?

Wed Feb 01, 2012 1:29 pm

So whats the purpose of using batteries anyway? I mean yeah it would be a fun project but adding a battery pack still wouldn't make this a mobile device... you still need a monitor, keyboard, mouse (depends).

I was going to try to hook mine up to an old gameboy for the screen and battery pack, then developing some games but I got to thinking I'd rather use it as a home theater system, it's perfect for the bill.

I also have the idea of taking an old laptop, stripping out the insides (and reinforcing it) and attempting to wire the RaspPi to the various components, creating a RaspPi laptop.

This is all theoretical of course, chances are I'd be screwed by drivers or something which I have no idea how to write or modify, interesting thought though.

Garacesh
Posts: 17
Joined: Wed Jan 25, 2012 12:16 pm

Re: Rechargeble batteries suitable for the RPi?

Wed Feb 01, 2012 2:26 pm

Because if you can hook a battery up to it, and a touch-screen (and install an on-screen keyboard) it WILL be portable There's a few touch-screen discussions going on here-and-there. I intend to buy a 2nd release Pi and hopefully by then someone'll have discovered an iron-clad working touchscreen.

Heck, even if I need a stylus I'd be happy. Has a more retro/techy feel.

That's what I hope to achieve, anyway. I assume some others are just going to use batteries for backup power, or heck, I dunno really. We all have our own ideas in mind.

mobeyduck
Posts: 173
Joined: Tue Nov 29, 2011 6:39 pm

Re: Rechargeble batteries suitable for the RPi?

Wed Feb 01, 2012 2:45 pm

Just because we can still sounds like a good reason

You can also add a wifi adapter and put a ssh client on your phone and use it in the train there are so manny possibilities

Garacesh
Posts: 17
Joined: Wed Jan 25, 2012 12:16 pm

Re: Rechargeble batteries suitable for the RPi?

Wed Feb 01, 2012 5:29 pm

mobeyduck said:


Just because we can still sounds like a good reason


Works for me! xD

thewimreaper
Posts: 4
Joined: Wed Dec 28, 2011 12:36 pm

Re: Rechargeble batteries suitable for the RPi?

Thu Feb 02, 2012 12:27 am

would it be possible to use one off those on the go emergency phone battery chargers.

or even an solar charger like the ones from philips of duracell.

6+11= i hate math

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