Powering a 5v USB electric blanket with 18650 batteries?

[JEDI]

http://www.ebay.com/itm/USB-Powered...ric-Warming-Heating-Blanket-Pad-/131826353540
(31" x 18")

I have lots of 2000mAh 18650 batteries.

I was thinking of powering the usb blanket with this 6 cell 18650 power bank. (I supply the batteries.)
http://www.ebay.com/itm/5V-4port-US...harger-DIY-Box-For-Smart-phone-/292067500000?

what do you think?
will it work?
if so, for how long?

 

[mindless1]

There is no way to know. We could assume your batteries are accurately rated at 2000mAH, and assume they have practically all their initial capacity remaining after however many recharge cycles they've been through. We could even assume that power bank is in the neighborhood of 80% efficient and do some math like:

6 x 2Ah * 0.8 * 3.6 / 5.0 = 6.9 Ah output

The problem is, we don't know the blanket power input, and I wouldn't even trust any figure given for a generic Chinese product if I had it. However let's suppose they tried to adhere to a 500mA spec, then you have 6.9AH/0.5A = 13.8 hours.

That's if it works. I mean in a perfect world it would but in a world where a power pack only costs 79 cents, my greatest concern would be monitoring voltage over a test run to make sure it doesn't overly charge or discharge the cells.

However, I had assumed you were talking about having six loose cells while that enclosure looks like it has no electrical contacts so you have to DIY spot weld them together.

Also if it is only 500mA, a 2.5W blanket isn't going to feel very warm.

 

[lxskllr]

Also if it is only 500mA, a 2.5W blanket isn't going to feel very warm.

I'm wondering what that even is. Sounds like a gimmick. Another 'usb all the things' device. I produce more body heat than that blanket ever could.

 

[Paperdoc]

Yeah, assuming the 0.5 amp USB2 limit gets you to 2.5W power, and that is miniscule! Even if you assumed the pad could actually use as much a 2 amps (that's a high number for a USB charging port), you'd get 10W out of it. For comparison, I've examined heated travel mugs for coffee, designed to be plugged into an auto cigarette lighter socket to keep your coffee warm. Lately, there are a lot of those things that come with an optional connector to plug into a USB2 port instead. That has led to MANY people complaining that they do almost nothing and never keep the coffee hot, so they must be defective.

From experience with these heated mugs, I have found that ones able to use 15W or less (using a 12 VDC source) cannot keep a mug hot - it continually cools off. A 20W mug might do the job. A 35w mug can make the coffee too hot, and the best ones I've seen had a 35W heating element and used a thermostat to regulate the temperature.

So, OP, Consider that 15W heating capacity a partially-insulated small container cannot keep things very warm and it takes much more than that for real heat in a small space. Now, what does a heating pad require to generate a real heating effect? A LOT! more than 2.5 or 5W! Even if the unit's heating element can take 3 or 4 amps - VERY unlikely, or it would not work with a USB2 source - that would radically reduce the period of use of that battery pack you are considering.