TeaAddict
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Is battery pack strong enough?

Wed Nov 14, 2012 10:18 pm

Hello. In my local Walmart, I have seen energizer battery packs for sale, and I was wondering if one could power my Pi. I'm not sure if it is enough. It outputs 5V and has 800mAh. Didn't say how much current it could output on the package, but at 800mAh, if the Pi consumes 500-700mA, this battery should power the Pi for over an hour right? I just wanted to ask before I buy it.

Also, are there any other compatibility issues other than power output when it comes to batteries? Note: it does have a Micro-USB connector.
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redhawk
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Re: Is battery pack strong enough?

Wed Nov 14, 2012 11:25 pm

I had a quick look on the Walmart website but couldn't find anything, do you have the model number or product link??

If this helps I have the black version of this USB battery pack charge it's sold under a different brand in the UK - http://www.amazon.com/5000mAh-External- ... 00852YV6E/
It delivers 5.3v @ 1A max and claims to have a battery capacity of 5000mAH, needless to say it was capable of powering my PI with Wifi adapter.
As for how long it lasts while on full charge I cannot say I've never really tested it to find out.

I did do a recent experiment with 2 x AA 3000mAh Ni-MH batteries and a 5v step-up buck converter.
I got about 1 hours worth of X-Windows and streaming online mp3 music (Digitally Imported) via LAN before the PI died from lack of power. :lol:

Richard S.

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Re: Is battery pack strong enough?

Thu Nov 15, 2012 6:09 pm

lol I couldn't find it on the website either!

BTW your link is broken :( could you try it again I would like to take a look at it.
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Re: Is battery pack strong enough?

Thu Nov 15, 2012 6:21 pm

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redhawk
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Re: Is battery pack strong enough?

Thu Nov 15, 2012 6:23 pm

Yes sorry about that I copy and paste my original post because I spotted a mistake, it corrupted the URL in the process.

The link is - http://www.amazon.com/5000mAh-External- ... 00852YV6E/

My battery pack:
Image

Richard S.

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Re: Is battery pack strong enough?

Thu Nov 15, 2012 8:31 pm

Very cool looking setup! But wouldn't it be easier to just connect the battery to the Pi's Micro-USB port?

Also, what about just connecting four rechargeable Ni-MH batteries to the +5V GPIO, or stripping the insulation off a Micro-USB connector and wiring it to the four batteries?

(Forgive me if this is a dumb idea I am a bit new to electronics :oops: )
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redhawk
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Re: Is battery pack strong enough?

Thu Nov 15, 2012 9:13 pm

The circuit in the photo is from one of my electronics projects a digital power on / off switch which is why the PI isn't directly connected to the battery pack - http://www.raspberrypi.org/phpBB3/viewt ... 64#p205664

As for 4 x rechargeable Ni-MH batteries this is one way of powering the PI however you are only providing 4.8v (4 x 1.2).
Another problem is when batteries discharge their total output voltage tend to drop under load this may cause the PI to reboot, shutdown or trouble with USB devices.
The solution for this is to use a step-up buck converter it's a little power board that takes an input supply of 2 - 5v and provides a stable output of 5.2v
(step-down buck converters are similar but take a higher input voltage i.e. 12v and convert it down to 5.2v)
That way you're guaranteed to a) provide a stable voltage for the PI and b) to use as much charge from your batteries as possible.

Richard S.

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Re: Is battery pack strong enough?

Thu Nov 15, 2012 9:39 pm

But the Pi is designed to take 5V. if you apply 5.2V, wouldn't that damage the Pi, USB devices, HDMI, etc?
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redhawk
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Re: Is battery pack strong enough?

Thu Nov 15, 2012 10:09 pm

But the Pi is designed to take 5V. if you apply 5.2V, wouldn't that damage the Pi, USB devices, HDMI, etc?
Internally the PI's CPU and RAM is powered from a 3.3v regulator (RG2) therefore you shouldn't worry about the voltage being a little over 5v.
You need the extra voltage to compensate for losses from the power cable and the on-board polyfuse (F3), also attached USB devices especially wifi dongles would cause the voltage to drop further.

You may start out with 5.2v but in practice you'll actually end up with a lot less than 5v when you're using your PI with USB devices.

For more information on PSU please check out - http://elinux.org/RPi_Hardware#How_Can_ ... dequate.3F

Richard S.

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Re: Is battery pack strong enough?

Fri Nov 16, 2012 1:46 am

Could you link me to a good and simple tutorial on how to make a Buck Converter? I cant find any that are on my skill level.
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redhawk
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Re: Is battery pack strong enough?

Fri Nov 16, 2012 10:49 am

Building a buck converter is easy, making one that provides high current at continuos 5v is not.
If you want to power your PI with a buck converter then I would suggest you purchase a ready made board i.e.

Step-up example:
http://www.ebay.com/itm/DC-DC-Converter ... 1016633368

Step-down example:
http://www.ebay.com/itm/LM2596-DC-Step- ... 0942757086

These boards come in a variety of specs (working voltage output current) you'll need to find one that suits your needs.
Most come from China / Hong Kong so there would be a postal delay, however they are definitely worth the wait.

Richard S.

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Re: Is battery pack strong enough?

Fri Nov 16, 2012 10:52 am

redhawk wrote:Building a buck converter is easy, making one that provides high current at continuos 5v is not.
If you want to power your PI with a buck converter then I would suggest you purchase a ready made board i.e.

Step-up example:
http://www.ebay.com/itm/DC-DC-Converter ... 1016633368

Step-down example:
http://www.ebay.com/itm/LM2596-DC-Step- ... 0942757086

These boards come in a variety of specs (working voltage output current) you'll need to find one that suits your needs.
Most come from China / Hong Kong so there would be a postal delay, however they are definitely worth the wait.

Richard S.
Instead of looking at ebay these parts and many others are available in UK from MANY resources Maplins CPC Farnell Rapid ............... With less delay and easier to return when faulty
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redhawk
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Re: Is battery pack strong enough?

Fri Nov 16, 2012 12:44 pm

Actually I believe TeaAddict is from the US we don't have Walmart here only Asda in the UK. :)

As you rightfully said you can purchase boards from local suppliers but their asking price tends to be 2 to 3 times more.
So I guess this is a question of either waiting 2 to 3 weeks for overseas postage or pay double for a few days delivery.

As for RS, Farnell and Maplin I've already searched for "buck converter" and "power module" but there isn't really much to choose from and certainly not within a reasonable price range.

Richard S.

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Re: Is battery pack strong enough?

Fri Nov 16, 2012 12:53 pm

Fine wait for 2-3 weeks get a cheap one with poor datasheet.

Often the ones on ebay are cheap for a reason, where as the ones from local sources are more likely to be ones that actually have good specs and follow the specs when you get them.

There are many places to find DCDC converters (the normal term used in the industry)

2-3 tiumes the price is not always the case when you also consider shipping costs, I have got things cheaper and quicker rather than pay up 5 times the part cost in shipping.

ebay is a great place to get clone components that may not actually work as they should do in my experience.
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redhawk
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Re: Is battery pack strong enough?

Fri Nov 16, 2012 1:09 pm

I agree not everything from China is all bells and whistles (lot of fake electronics) but from what I've ordered so far on eBay has been more than satisfactory for the price.
It's not ideal to run a PI off batteries anyway but a buck converter would at least provide a longer lasting stable power supply which wouldn't be possible with batteries alone.

Richard S.

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