A senior in highschool no degree yet and I haven't taken any electronics classes. I am fairly knowledgable when it comes to computers if that gives you any baseline for electronic knowledge
Nichrome Wire Heater
- Thread starter andregtable
- Start date
Let's assume that a car fender is 8" wide covering a radius of 15" and a semi-circle. That is about 360 square inches of fender well area to heat per fender.
If 1 watt per square inch is enough, then you will need 720 watts to heat it. I think a cars alternator can handle 1500 watts (luxury car with heated rear defrost (150 wats) heated seats (2x100 watts), premium sound (40 watts), fog lights 40 to 55 watts each. 2 x 55 watts for headlights, ... In other words, you will manage about a 1/4 watt per square inch with out overwhelming the electrical system. At that, you better hope it stays really close to 32 F so you have enough power to melt anything.
According to this site:
Most late model alternators produce 120 to 155 amps or more. Current output increases with engine speed, from around 20 to 50 amps at idle up to the unit's maximum output at 2,500 RPM or higher (refer to a service manual for the exact charging output specifications for your vehicle).
That means that your estimate is about ballpark correct, I think...
@andregtable, consider this for a moment... do you think the power output of an ordinary hair dryer (which is about 1,300W) would be enough to accomplish what you want?... because a normal car's alternator is not up to the task.
I only want to heat a 10x6 area where the snow builds most. My car has a 180amp alternator and my electrical draws 100 amps max during winter (both heated seats on, rear defroster on, heated ac, high beams) i have a chart that tells me how much each thing draws the defroster draws 30amps and the lights and such draw around 5 so there is some room to work. Obviously im designing this for my main car but i would like to be able to use it on my other cars, hopefully with minimal tweaking.
Chill. It takes time to understand the project and do the research.
So NOW you define the area you want to heat.
Refusing to reveal your goal wastes my time. I feel annoyed with you.
Nobody asked for it. If you're annoyed and your time is being wasted feel free to leave. Im asking for help, if i knew what was needed to get the answer i wouldn't be here.So NOW you define the area you want to heat.
Refusing to reveal your goal wastes my time. I feel annoyed with you.
You didn't ask for help?
Please do not use my math or look-up tables.
Cant say im not going to use your math. I said upfront that I can answer any questions you have. Like i said in my last post i clearly wouldn't need help if i knew what was needed to solve my problem.
Post 12 paragraph 3.
Not really. Very few stock automotive alternators can support continuous high current loads.
Unless you have a aftermarket commercial application unit and all the oversized wiring to support it your stock alternator and wiring will heave a meltdown if it tries to run near its limits for more than a few minutes.
Problem solved. $35. http://www.ebay.com/itm/200-Watt-12...809732?hash=item2eec692684:g:rXIAAOSwLN5Whfs~
I think you need to double that for the total load. Doesn't the car have 4 wheel-wells?
Dr.killjoy
- Joined Apr 28, 2013
- 1,196
The heating mat is a great idea but also remember that snow and ice are also great insulators .. I would try using pam or some anti stick spray in conjunction with the mat and I would just keep the mat warm to slightly hot to the touch in order not to damage the car..
Here are some more numbers to play with.
Thermal conductivity of ice = ~1.6W/metre/°C
So for a 1cm thick ice layer, to maintain the temperature at 0°C on the car body side of the layer with -10°C in the wheel well you would need ~1.6*10/0.01 = ~1.6kW per sq metre.
Thermal conductivity of ice = ~1.6W/metre/°C
So for a 1cm thick ice layer, to maintain the temperature at 0°C on the car body side of the layer with -10°C in the wheel well you would need ~1.6*10/0.01 = ~1.6kW per sq metre.
Thats great but i dont want to buy something i want to learn how to make it. I know that is always an option but how fun is it when you just buy something? I'm trying to learn here
I think I'd start small and see how it goes with a prototype or series of them. In my experience very few blue-sky designs work great - or at all - on the first shot. But that's fine - that's how you learn what the important variables are. When you don't know what you don't know, you have to collect data. Some factor not yet identified may turn out to be the critical factor. The modern incandescent lightbulb came about after Langmuir's discovery that filling the bulb with inert gas was far superior to the vacuum used by Edison and others before him.
So I'd start with a 10-15A heater. Any car will probably have room to add a 10-15A load without concern for heavier wiring, adding relays and all that. You can just tap into existing circuitry. You'll only have ~150W, but that may be enough to learn if the idea has merit.
Consider upgrading from nichrome to René 41.
I think it's been said before but I'll reiterate: You don't need a temperature-controlled feedback loop to control your wire, you need to control the current through it. A given piece of wire will have some maximum current it can tolerate without getting too hot. Let's say that's 20A. You will operate well below that, say 10A. That amount of power will establish a ∆T between the wire and the environment, and heat will flow from hot to cold.
The temperature of the wire and the ∆T will vary with ambient conditions, but that's OK. You're not incubating eggs, you're melting ice. That requires heat flow, not a temperature. (Obviously you have to have a temperature above freezing.)
How do you control current? There are circuits to control current but you can likely achieve what you need by the clever choice of wire. You'll need a table of wire properties and to do the math to simulate a wire based on your inputs of length and gauge. You might choose a gauge and length of wire that will draw 10A from a 13V supply. Done. If you cannot make self-limiting work, and need to limit the current externally to the coil, we can guide you current-controller options. There are tons available because this is exactly what automotive LEDs need, so you can easily buy one. The circuits can be fairly simple if you'd prefer to build one.
So I'd start with a 10-15A heater. Any car will probably have room to add a 10-15A load without concern for heavier wiring, adding relays and all that. You can just tap into existing circuitry. You'll only have ~150W, but that may be enough to learn if the idea has merit.
Consider upgrading from nichrome to René 41.
I think it's been said before but I'll reiterate: You don't need a temperature-controlled feedback loop to control your wire, you need to control the current through it. A given piece of wire will have some maximum current it can tolerate without getting too hot. Let's say that's 20A. You will operate well below that, say 10A. That amount of power will establish a ∆T between the wire and the environment, and heat will flow from hot to cold.
The temperature of the wire and the ∆T will vary with ambient conditions, but that's OK. You're not incubating eggs, you're melting ice. That requires heat flow, not a temperature. (Obviously you have to have a temperature above freezing.)
How do you control current? There are circuits to control current but you can likely achieve what you need by the clever choice of wire. You'll need a table of wire properties and to do the math to simulate a wire based on your inputs of length and gauge. You might choose a gauge and length of wire that will draw 10A from a 13V supply. Done. If you cannot make self-limiting work, and need to limit the current externally to the coil, we can guide you current-controller options. There are tons available because this is exactly what automotive LEDs need, so you can easily buy one. The circuits can be fairly simple if you'd prefer to build one.
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