Low voltage Low heat, battery powered heater

[nmeeker87]

Hey guys! I have been following the forum for quite some time now. With all of you smart people out there, I am hoping you can help me design a heater, or at least lead me in the right direction.

What I am attempting to create is a battery powered heater, to maintain a temperature of between 40 degrees Fahrenheit and 60 degrees fahrenheit. I have done quite a bit of research. I have thought to use Nichrome wire, a total of about 36 inches.

So the known so far is, 36 inches, and a temperature of about 50 degrees. However here is the kicker:

I need to power this via battery, during the winter. I will use thermal switches to begin and end the circuit. So it will not run constantly. I estimate it will run 8 hours a day. So at 8 hours a day, I need 36 inches of nichrome wire to heat at 50 degrees with NO maintenance for around 4 months. 8 hours x 120 days is 960 hours run time. I realize this is quite a demand, and I'm not sure if i can get this done, but I'm sure its possible. Problems are made to solve right?! The battery type is an unknown, and the gauge of the wire unknown.

Any advice guys would help. Battery type? Configuration? Nichrome Wire gauge?

Thanks guys!

 

[Bystander]

What's the heating load? Or, the heat leak you're fighting with this heater? No maintenance? You're running fairly heavy duty automotive batteries flat at 5 watts over 4 mos. at a 1/3 duty cycle.

 

[nmeeker87]

So, the heating load I would like to ignore, and just maintain the goal of heating that wire to 50 degrees. And I was hoping not to use such a heavy (weight) battery. I thought possibly using D batteries in a series or lantern batteries in series to increase maH. Possible ?

 

[Bystander]

the heating load I would like to ignore,

You can't --- it defines how much energy is required.

 

[NascentOxygen]

So, the heating load I would like to ignore, and just maintain the goal of heating that wire to 50 degrees. And I was hoping not to use such a heavy (weight) battery. I thought possibly using D batteries in a series or lantern batteries in series to increase maH. Possible ?

You need to indicate what it will be heating and how fast it will be losing heat. If you were to enclose the nichrome in an ideal thermos flask then once the wire reached desired temperature you could (in theory) disconnect the electricity and the nichrome wire would remain at that temperature!
But it could hardly be termed a heater when it isn't heating anything. http://thumbnails112.imagebam.com/37333/0363e9373324851.jpg

 

[psparky]

Are you heating some type of shack deep in the woods?

If so, may want to consider insulation around whatever you are trying to keep warm. This will keep your battery demand down.

 

[Sommerfeldt]

This is interesting - I've been working on something similar, and I'm building a protoype right now.

I've got the same issue, however - I don't know what to do about a heat source.

I don't mean to hijack the thread, but to explain quickly - I'm building a battery powered fan heater, designed to run for 2 - 3 hours / day, on a 12v 5500 mAh battery, to be recharged w/solar power. Fan is 0.48W, 0.04A, so that shouldn't take up much battery time.
My goal is to heat a space of about 12 m3 to ~35F in 2-3 hours, from as low as 14F.

Now, I don't know if it's possible (having NO science background or foundation), but I'd like to try it. :D

-S-

 

[NascentOxygen]

This is interesting - I've been working on something similar, and I'm building a protoype right now.

I've got the same issue, however - I don't know what to do about a heat source.

I don't mean to hijack the thread, but to explain quickly - I'm building a battery powered fan heater, designed to run for 2 - 3 hours / day, on a 12v 5500 mAh battery, to be recharged w/solar power. Fan is 0.48W, 0.04A, so that shouldn't take up much battery time.
My goal is to heat a space of about 12 m3 to ~35F in 2-3 hours, from as low as 14F.

Now, I don't know if it's possible (having NO science background or foundation), but I'd like to try it. :D

-S-

Hi, and again ... http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

Your 5.5AH 12V battery is approx 60 watt-hours max. So the absolute best you can hope for is that it will operate a 30 watt light globe for 2 hours. You can picture the amount of heat, it's the same as a 30 watt incandescent bulb in your house lighting. It will be hot to touch, but probably not take the chill off a room, alas. Heating is a greedy use of energy.

 

[Sommerfeldt]

Hi! Thanks, and thanks for the reply.

Heating is an energy hog for sure, that's the massive issue. However, it's not for a room per se, it only about 12 m3, which isn't very big at all. Would it be possible to somehow calculate the energy requirement to raise the temperature in that kind of space from say 15 to 35 F?

60 Wh isn't much, but there are hand warmers w/ ~5000mAh which keep the heat for about 3 hours - I don't know how that would translate int raising the temperature of air, though. :P

-S-