nerdydude101
Posts: 25
Joined: Mon Jul 01, 2013 12:18 am

Recommendations on how i should proceed?

Fri Aug 01, 2014 12:16 am

So i want to make a portable raspberry pi media center that will last at least 2-2.5 hours, i have all my parts scoped out:
•the pi (obviously)
•The screen: (http://www.dx.com/p/7-digital-lcd-scree ... 9NZYWNIpU0)
•a keyboard: (http://www.amazon.com/FAVI-FE01-BL-Wire ... b+trackpad)
•for a case i don't exactly have easy access to a 3d printer so i will be using my imagination and a little innovation (so whatever it will fit into, a pencil box, I've got some container like things, just whatever basically)

aside from this i will be using some flash drives to store movies, i think the os is xbmc (i can never remember the name). My issue comes with powering all of this, i have asked around and people said my best bet would probably be to use LiPo batteries, but i would need a ~19v one and i would need 2 5,000mAh ones to get ~10,000 mAh which is just super expensive, so i thought that maybe i could use a single LiPo battery (somewhere around the 12v i need for the screen) specifically for the screen, and maybe a portable battery bank with usb ports like this one (http://www.amazon.com/10000mAh-Dual-Por ... ttery+bank) or similar, haven't decided on which one to use, but my question is, is it plausible? or for that matter, will it even work? It would provide the 5v 2A for the pi and the LiPo battery will give the screen 12v, so what are the issues i should be considering here?

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AndrewS
Posts: 3625
Joined: Sun Apr 22, 2012 4:50 pm
Location: Cambridge, UK
Contact: Website

Re: Recommendations on how i should proceed?

Fri Aug 01, 2014 1:13 am

If you've got a 12V power supply, you can also use that to power the Pi with something like http://www.adafruit.com/product/1385

nerdydude101
Posts: 25
Joined: Mon Jul 01, 2013 12:18 am

Re: Recommendations on how i should proceed?

Fri Aug 01, 2014 2:36 am

This in parallel with the wires to the screen would give the screen 12v to then from what I understand( just confirm I understand please haha), just out kf curiosity though, would what I was doing have worked? I don't see any issues with tk but I commonly over look things, also is the +-5% on the product you linked dangerous to the pi?

drgeoff
Posts: 11373
Joined: Wed Jan 25, 2012 6:39 pm

Re: Recommendations on how i should proceed?

Fri Aug 01, 2014 10:52 am

nerdydude101 wrote: also is the +-5% on the product you linked dangerous to the pi?
The RPi is quite OK with 5.25 volts (5 + 5%).
Quis custodiet ipsos custodes?

nerdydude101
Posts: 25
Joined: Mon Jul 01, 2013 12:18 am

Re: Recommendations on how i should proceed?

Fri Aug 01, 2014 4:00 pm

I can't seem to find any 12v 5,000 mAh LiPo batteries, do you know of any? Also, how exactly do they charge? I've never specifically used LiPo so do they have a port or a chord or something or will I need to buy a charger? I would prefer to not have to take it out of the enclosure but it won't really be a problem

jaybee007
Posts: 20
Joined: Thu May 29, 2014 8:49 pm

Re: Recommendations on how i should proceed?

Fri Aug 01, 2014 5:18 pm

I'm in the process of creating exactly what you are talking about ;) .
I have used an old xbox 360 hddvd for my case it has the original power board still inside and that provides me with 2x12v,2x5v,2x3.3v and 2xgnd so it is ideal. (very cheap from eBay as it's obscelete tech,blu ray won that war ), a 4.3" ssd1963 screen, I tried to upload a pic to show you but it's apparently to large a file. The only problem would be the size ,it's quite big but a bonus is you just use the one cable to power and charge the device . I have made it portable buy using a 5v power bank but to be honest this is not working very well. It only lasts around 20 minutes I think you may need a bigger supply to last the amount of time your looking for. Mine is only 2800mah

nerdydude101
Posts: 25
Joined: Mon Jul 01, 2013 12:18 am

Re: Recommendations on how i should proceed?

Fri Aug 01, 2014 5:31 pm

Yeah, with the screen I'm trying to use and the pi I need 10,000 mAh to run for ~2 hours, which is quite a lot of money for the battery's, the overall cost if this thing is around like $240 without the usbs and about half of that is just the batteries, LiPo batteries seem to be ideal I just don't know about how they charge or where to find a decent priced 12v one (the one I find is 14v which is too much but I may be able to work with it, not sure)

drgeoff
Posts: 11373
Joined: Wed Jan 25, 2012 6:39 pm

Re: Recommendations on how i should proceed?

Fri Aug 01, 2014 9:16 pm

nerdydude101 wrote:Yeah, with the screen I'm trying to use and the pi I need 10,000 mAh to run for ~2 hours, which is quite a lot of money for the battery's, the overall cost if this thing is around like $240 without the usbs and about half of that is just the batteries, LiPo batteries seem to be ideal I just don't know about how they charge or where to find a decent priced 12v one (the one I find is 14v which is too much but I may be able to work with it, not sure)
You MUST use the proper charger for LiPo or Li-ion batteries. Otherwise they are exceedingly dangerous. Explosions and fires. If you are lucky and are not killed you may find your insurance company refuses to meet your medical claims and house rebuilding costs.
Quis custodiet ipsos custodes?

nerdydude101
Posts: 25
Joined: Mon Jul 01, 2013 12:18 am

Re: Recommendations on how i should proceed?

Fri Aug 01, 2014 10:28 pm

Well then using a 12v Li-ion battery with what I'm doing work ok or is there any serious danger (I'll make sure to get the proper charger but when it comes to the battery powering what I have (one 12v screen and using the UBEC DC/DC Step-Down (Buck) Converter - 5V @ 3A output to step it down for the pi) is there anything I should know?)

dj505
Posts: 5
Joined: Sat Aug 02, 2014 9:03 pm

Re: Recommendations on how i should proceed?

Sat Aug 02, 2014 9:29 pm

If you want a reliable power source and you have access to a Costco (and a membership for the store) or even the Source/Radioshack (depending on if you are Canadian or American) or any other electronics store you can get a portable battery pack called a Mophie for around $50 CDN, charge the Mophie for about an hour or two with a Micro USB cord (Like the Pi) and use it to power the Pi. You'll need a cord that is Micro USB to USB. The Mophie itself has one USB port on it used for outputting the charge to the device, and when you wat to start powering it just press the button on the side. Best part is it works for anything you have a USB adapter for, up to and including a tablet such as an IPad or Nexus or whatever brand/model. There are a few different models but all (except the phone cases that charge the type of phone they're meant for) should work perfectly. It holds enough charge to power an iPhone 5 twice (fully) and should hold enough juice to power the screen and any peripherals like mice and keyboards and maybe even small speakers, too. It will definitely last a few hours. Hope this helps :D

rfrazier
Posts: 60
Joined: Fri Jul 25, 2014 5:14 am

Re: Recommendations on how i should proceed?

Sun Aug 03, 2014 5:04 am

Nerdydude,

Regarding what @drgeoff said, as far as I know ANY battery with Lithium (Li) chemistry can explode or catch fire. I would strongly recommend a pre made battery pack like those that have been discussed, with it's own pre designed charger. As @dj505 mentioned, there are many of these 5V packs available. If you want 12V, you could get or build a 5V - 12V converter, with proper current levels, or possibly use a separate 12V battery pack with either NiMH, NiCd, or Sealed Lead Acid chemistry. You may be able to find a pre made pack for that, or could consider building your own pack from cells. You still need a proper charger for those, and it's different from Li batteries. But, those don't (USUALLY) explode. Overcharge a lead acid battery (generating hydrogen), and it can explode. If you don't mistreat them, sealed lead acid batteries are good for 12V sources. A visit to a Batteries+Bulbs ( http://www.batteriesplus.com/default.aspx ) store, if you have any around, or their web site, can be quite interesting. They have all types of batteries, many of which might work for a project like this.

These Wikipedia articles have lots of info, maybe too much, but you can skim over them.

http://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery
http://en.wikipedia.org/wiki/Lithium-ion_battery
http://en.wikipedia.org/wiki/Nickel%E2% ... um_battery
http://en.wikipedia.org/wiki/Nickel%E2% ... de_battery

For the first two primarily, take note of paragraphs relating to explosions, safety, and transport restrictions.

Stay safe.

Sincerely,

Ron
(PS - If you email me and don't get a quick response, you might want to send again after a couple of weeks. I don't always see new email messages quickly.)
Ron's Tech Rant Blog: techstarship.com - Blog RSS: techstarship.com/feed/
Ron Frazier

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