Hello,

I have an 80-meter nichrome wire and I want it to heat up to 40 degrees Celsius maximum (30 to 40 is ok). I want to connect it to a battery that is enough to make it hot for at least 10 hours.

The ambient's temperature is negative 15 degrees Celsius.

What is the diameter for this wire? what is the resistance?

What are the spec of that battery in this case?

 

energy in equals energy out. You need to calculate, or experiment to find out what energy is required to sustain your temp given the environmental heat conductance. Your battery must then provide that over the term. The wire is simply a state converter.

 

What is the diameter for this wire? what is the resistance?
What are the spec of that battery in this case?

I don't think it would be practical.
80 meters of 24 gauge nichrome 60 wire has a resistance of 440 ohms. Using Jacobs nichrome wire calculator which would not go below 200F the voltage required was 774 volts at 1.76 amps. Estimating appx 675 volts at 1.53 amps for 40C

 

I don't think it would be practical.
80 meters of 24 gauge nichrome 60 wire has a resistance of 440 ohms. Using Jacobs nichrome wire calculator which would not go below 200F the voltage required was 774 volts at 1.76 amps. Estimating appx 675 volts at 1.53 amps for 40C

what if I reduce the length to 10 meters instead? could you tell me the specs of the wire in that case?

 

what if I reduce the length to 10 meters instead? could you tell me the specs of the wire in that case?

Estimating the wire requires 1.53 amps.
10 meters of nichrome 60 wire has 55 ohms of resistance, 440/8 = 55
Voltage required: 55 x 1.53 = 84.15 volts

 

What is the ambient material? Its thermal conductivity will affect the answers you're looking for.

 

It also depends on the shape of the wire. If it is tightly coiled, it will take much less energy than a straight piece of wire.

And is it in open air or in contact with something else?

This cannot be answered in general terms, you would almost certainly have to experiment with it.

 

Just guessing; perhaps the TS has heated clothing fabric in mind?

 

Just guessing; perhaps the TS has heated clothing fabric in mind?

Hope he has a motorized cart to carry the battery. I have a pair of heated gloves, the two cell 18650 battery (per glove, 4 cells for the pair) lasts maybe 2-3 hours on a charge.

 

It also depends on the shape of the wire. If it is tightly coiled, it will take much less energy than a straight piece of wire.

And is it in open air or in contact with something else?

This cannot be answered in general terms, you would almost certainly have to experiment with it.

It's in contact with a fabric of polyester ,

 

Being 'in contact' with the fabric doesn't tell us much. Is it totally surrounded by the fabric? How thick is the fabric? What is the U-value of the fabric (or its thermal conductivity rating)? Is the wire straight, zig-zagged, coiled ....?
You will have to experiment with a sample of the wire and fabric, as Bob suggested.