Take a stab at it what do you think? heat element/battery

[John Crosby]

This is a question I am throwing out to everyone. Let me give you the scenario below and I would like your suggestions (and reasoning) for items you recommend. Let's see what you come up with!
SCENARIO: Extremely safely heat a small (12" x 20" ) thin wafer heating element with a small sized rechargeable battery source. Must be very safe, no overheating, no explosions, no overheating of battery pack, and as lightweight as possible. MUST be very economical and products already available in bulk production.
-must reach heat setting extremely quickly (would like to hear sample time frames in your suggestions)
-heating element encased on plastic mold, forming thin plastic sheet with small battery pack attached to it
-"low" heat in the 90's F, "high" heat around 105+-F
-Must reach desired heat setting and hold for 20 minutes+-, then will automatically shut off and not be used for many hours
-Would prefer to get numerous uses from one charge, but at least 2-3 uses is required
-battery pack needs to be in flat linear arrangement and can be the width of a single battery and as long as 15-20 inches(basically, can't stack the batteries, must align them in a straight line)...and remember, as light as possible
-Does not have to cool quickly
-battery pack will be inches away from the heating element
-will also need to power battery life display, and low,high light
-finished product will be form molded plastic encasing battery (with charging port exposed) and heating element with controls, etc.
-finished product will be somewhat rigid, but will require slight flexing ability but will not be folded or creased, etc, like clothing

Questions (***most ECONOMICAL avenue for all questions that would support mass production***):
1.) What is the smallest type and size battery pack that would provide numerous uses (20 minutes of usable heat with 3-12 hours of downtime) on a single charge? Question #2 may determine power source.
2.) What would be the most economical flat wafer heating element to use in this application (carbon fiber, Mica, aluminum sheet, etc.)? Question #1 may determine heating source.
3.)What would be the ultimate small rechargeable battery source paired with the ultimate wafer type heating element source that is currently on the market that could easily be paired together? Looking for point and click ideas that you would suggest if you had to pair these two items together today from readily available extremely economical products to mass produce this product.

**Bonus**= On a lighter note, if money was no option and production/manufacturing was not a hindrance, what would you use!?

NOTE: I am not a physicist but I think I've covered most of the variables that you should need to answer this question. If I've missed something major, please let me know. Thanks everyone!

 

[berkeman]

Welcome to the PF.

What is the context of your question? Why are you wanting to do this? What have you tried so far?

 

[John Crosby]

Want to get more knowledge for a product that I am designing and would like to get info from people who love this sort of thing. Haven't tried anything, but it's a pretty common use, just wanted to try to nail down a "best fit" through your feedback.

 

[berkeman]

Want to get more knowledge for a product that I am designing and would like to get info from people who love this sort of thing. Haven't tried anything, but it's a pretty common use, just wanted to try to nail down a "best fit" through your feedback.

We prefer that folks show some effort of their own before we offer suggestions and ideas. Please do a little reading, and tell us some typical ways this can be approached...

 

[John Crosby]

Absolutely...although I didn't want to cloud the waters with my suggestions. A 12V rechargeable battery pack application with a Mica heater plate seems to be the most effecient/economical option, but not sure if that's overkill to sustain 100 F for 20 minutes or if that would allow for numerous run times separated by potentially 12 hours of downtime between each use. The benefit of a small solution is cost and weight, and the desired perfect mix would be the cheapest solution that will effectively provide numerous uses before a charge is needed. A 7.2V 2900mAh lithium battery could be the way to go as well for instant heat, but I don't know what Ah would be most efficient for this purpose. Honestly, there isn't much information to be found on heating using a battery source because it's not very efficient, but for the short duration of heat I need and the relatively moderate temp I am trying to achieve (and the requirement to use grid electricity) it seems to be a good fit. I also need something that would require a very simple charging system...preferably something that just plugs into a wall
Also, I'm not sure if a Mica heating element is the most efficient/economical in this application, but it seems to be from the research that I've done. We don't need great flexibility, but it must be thin, and most importantly they are fairly inexpensive...but more knowledge in that area would be helpful as well.
I guess I'm looking for experience as opposed to knowledge, and I can't get that from reading more information so that's why I'd like your opinions.

 

[John Crosby]

Absolutely...although I didn't want to cloud the waters with my suggestions. A 12V rechargeable battery pack application with a Mica heater plate seems to be the most effecient/economical option, but not sure if that's overkill to sustain 100 F for 20 minutes or if that would allow for numerous run times separated by potentially 12 hours of downtime between each use. The benefit of a small solution is cost and weight, and the desired perfect mix would be the cheapest solution that will effectively provide numerous uses before a charge is needed. A 7.2V 2900mAh lithium battery could be the way to go as well for instant heat, but I don't know what Ah would be most efficient for this purpose. Honestly, there isn't much information to be found on heating using a battery source because it's not very efficient, but for the short duration of heat I need and the relatively moderate temp I am trying to achieve (and the requirement to use grid electricity) it seems to be a good fit. I also need something that would require a very simple charging system...preferably something that just plugs into a wall
Also, I'm not sure if a Mica heating element is the most efficient/economical in this application, but it seems to be from the research that I've done. We don't need great flexibility, but it must be thin, and most importantly they are fairly inexpensive...but more knowledge in that area would be helpful as well.
I guess I'm looking for experience as opposed to knowledge, and I can't get that from reading more information so that's why I'd like your opinions.

Meant to say "requirement NOT to use grid electricity"