USB in series?

R

robgendreau

Explorer
Anyone ever hack together a system to put some USB power sources together in series for 12v use? I think USB is standardized at 5.5v, so it would be three sources and voltage conversion down to 12.

I ask cuz I seem to have a bunch of LiOn USB output batteries now, but some of my stuff is 12v in. And I don't relish working with all those fiddly little USB wires, so I also wonder if there's a USB female breakout of some kind out there?

thanks,
Rob
 
1stDeuce

1stDeuce

Explorer
Well, a USB is only capable of some pretty small juice output, so even tripled, you're looking at ~3a total. Perhaps up to 6a if they're the charger type outputs... Not sure what you're thinking of running, but 6a isn't much for most 12v accessories, aside from phone chargers. Which would rather use one USB power supply by itself...

If the units were stand-alone, I guess you could put three of them together for 15V total, but I'm not sure your 12v electronics would like that. And 10V is too low for just about any 12v device.

Good luck!
C
 
rayra

rayra

Expedition Leader
I wouldn't bother, since most vehicles are littered with available 12v wiring you can add 12v power ports to. I'd be more inclined to wire them up in parallel (if that's even safe / workable) and keep the USB power sources for USB devices like phones, tablets, rechargable GPS devices. Or even USB-based lighting, portable work or area lights.
 
R

robgendreau

Explorer
Thanks, but I'm aware of the amperage limits (there is a new one coming, but most of the USB outputs in use are at most 2.1A, for fast charging some smartphones and tablets). The amps provided are more than enough for lots of stuff I use. BTW if you do need them in parallel there are cords for portable hard drives that do that.

And the point is to have a battery away from a vehicle. But turns out others have beat me to it; in searching for parts I've run across tons of 12v packs for cheap. They are using the same cells as what I've got now, but much friendlier connection possibilities, so it isn't worth it for me to dismantle what I've got (which I got free, hence the desire to convert them for 12 v use). Those high discharge rate LiPos for jump starting are getting cheaper too by the way; not optimal for max AH although they are around 12AH or so, and can serve double duty. Not sure about their longer term viability for discharge/recharge though.

thanks,
Rob
 
dwh

dwh

Tail-End Charlie
What kind of batteries? Bust 'em open and you'll find a bunch of lithium cells - probably 3.7v. String those together any way you like.

li-ion-cylnd.jpg
 
R

robgendreau

Explorer
That's doable but I'd want the protection circuit, and maybe the charging, included as well. Those batteries can do bad things when they misbehave, like bring down planes. The nice thing is that there are cheap little USB chargers that have all those components for less than I can buy them for separately, hence my original desire to make a 12v pack out of them. And yeah, a normal cell is 3.7v.

BTW the RC plane, copter and car enthusiast suppliers have the best prices on some of this stuff.
 
pugslyyy

pugslyyy

Expedition Vehicle Engineer Guy
R

robgendreau

Explorer
I guess I should wait; USB 3.1 type C will apparently do 3A. The just announced Macbook 12" will apparently sport that connector.
 
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