Voltage and heating circuits?

The boost converter can handle the ~5A plus start up surge? Can you just run the heater circuit off the battery direct?

George H.

At 12 volts, you'd get a bit more than half the heat that you'd expect at 16. No hazard. Try it and see if it's warm enough.

John

If the heater is indeed nothing but resistance, it won't do any harm at all, but you'll get a drastically reduced heat output. I'm way too lazy to do the math; if it's nichrome, the difference would be exaggerated, because nichrome has some insane tempco of resistance.

But there's very little danger that you'll burn the house down. :-)

Cheers! Rich

it will heat less powerfully by the ratio 12^2/16^2 which is 144/256, 9/16, or about 56% but it's not that bad, lead-acid batteries are usually around 13-14V ballpark 70-80%

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?? 100% natural

nichrome's tempco is very close to 0, stainless steel on the other hand goes up quite a bit from room temp to red-hot.

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?? 100% natural

Guntar Gunderson:

If you need more heath than half of the rated, maybe it's less expensive to buy another battery to be put in series with the one you have and build a simple, very low frequency, PWM controller, that will cost you about $5.

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It won't get as hot as it would running it on 16V.

Hm. I must have been thinking tungsten, as in bulb filaments.

Thanks! Rich

"Rich Grise is off his Drugs":

** Ni-Chrome has a large tempco ??

News to everyone that has ever used any.

Wot a moron.

.... Phil

"Rich Grise"

** Still wrong - dickwad.

In practice, the heat difference would be diminished compared to a simple resistance - cos as the applied voltage drops, so does the resistance of tungsten.

..... Phil

Uh, yeah, that's what I just said.

Thanks, Rich

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I was looking at the temperature dependence of Tungsten the other day (In a CRC). As with most pure metals the resistivity increases about linearly with temperature. The temperature coefficient has units of inverse temperature and one over it should be close to the temperature (in degrees K) of the reference temp. (20 degree's C or 293 degree's K) I think the numbers was something like 250 or 220K. ~4 parts per thousand.

Resistors have amazing tempco's in comparison.

George H.

** No dickwad - you said the direct opposite in fact:

" if it's nichrome, the difference would be exaggerated, because nichrome has some insane tempco of resistance."

Piss off - IDIOT !!

..... Phil

Yeah, and I stood corrected: After I was duly informed of my error, (see upthread, if you're a man) I said, and you can look above, "Hm. I must have been thinking tungsten, as in bulb filaments."

"Dickwad?"

Oh, well, guess you missed your Tourette's meds today.

But thanks for playing! Rich

You can't insult me if you can't even spell "f*****ad."

Please go take your meds.

Thanks, Rich

Guntar, are you still there? Just ignore the silly little flame wars. Phil has been doing that for years. Others have pointed out that heat from a resistor varies with the square of the voltage, so you might be able to get by with a single 12 volt battery, or two of them in series if you need more heat. But you don't have much control over the amount of heat you're getting that way. You could have an adjustable heater if you go with two batteries and a simple controller, whereupon you could simply turn a knob and get just exactly the amount of heat you need. I googled "adjustable duty cycle heater controller" and found some that run on 12 volts, but you would probably want two batteries in series (nominally

24 volts). If you're comforatable with a soldering iron, you could make your own controller -- it's a simple project, because all you need is a circuit that turns on and off at a low frequency, like once a second. You adjust the duty cycle and therefore the amount of heat. We haven't heard back from you, but there are people here that just love to offer their know-how on stuff like this. But you've gotta talk to us!