Voltage and heating circuits?

[Guntar Gunderson]

I have a simple heating circuit that takes 16V @ 3.5A. I want to run
it on a 12V-48A/hr deep-cycle battery.

Now, I can get a DC-DC boost converter for $80, NBD.

What will happen (generally) if I hook it up to the 12 volt source?
It doesn't have any solid state circuits... it's simply a resistance
device; I don't expect it to burst into flames. Am I violating any
basic safety rules if I plug into a lower voltage?

Gunz

 

[George Herold]

On Jan 12, 10:57 pm, Guntar Gunderson <f...@fee.com> wrote:

I have a simple heating circuit that takes 16V @ 3.5A.  I want to run
it on a 12V-48A/hr deep-cycle battery.

Now, I can get a DC-DC boost converter for $80, NBD.

What will happen (generally) if I hook it up to the 12 volt source?
It doesn't have any solid state circuits... it's simply a resistance
device; I don't expect it to burst into flames.  Am I violating any
basic safety rules if I plug into a lower voltage?

Gunz

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

George H.

 

[John Larkin]

On Wed, 12 Jan 2011 21:57:58 -0600, Guntar Gunderson <foo@fee.com>
wrote:

I have a simple heating circuit that takes 16V @ 3.5A. I want to run
it on a 12V-48A/hr deep-cycle battery.

Now, I can get a DC-DC boost converter for $80, NBD.

What will happen (generally) if I hook it up to the 12 volt source?
It doesn't have any solid state circuits... it's simply a resistance
device; I don't expect it to burst into flames. Am I violating any
basic safety rules if I plug into a lower voltage?

Gunz

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

 

[Rich Grise]

Guntar Gunderson wrote:

I have a simple heating circuit that takes 16V @ 3.5A. I want to run
it on a 12V-48A/hr deep-cycle battery.

Now, I can get a DC-DC boost converter for $80, NBD.

What will happen (generally) if I hook it up to the 12 volt source?
It doesn't have any solid state circuits... it's simply a resistance
device; I don't expect it to burst into flames. Am I violating any
basic safety rules if I plug into a lower voltage?

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

 

[Jasen Betts]

On 2011-01-13, Guntar Gunderson <foo@fee.com> wrote:

I have a simple heating circuit that takes 16V @ 3.5A. I want to run
it on a 12V-48A/hr deep-cycle battery.

Now, I can get a DC-DC boost converter for $80, NBD.

What will happen (generally) if I hook it up to the 12 volt source?
it's simply a resistance device;

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%

--
⚂⚃ 100% natural

 

[Jasen Betts]

On 2011-01-13, Rich Grise <richg@example.net.invalid> wrote:

Guntar Gunderson wrote:

be exaggerated, because nichrome has some insane tempco of resistance.

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.

--
⚂⚃ 100% natural

 

[F. Bertolazzi]

Guntar Gunderson:

I have a simple heating circuit that takes 16V @ 3.5A. I want to run
it on a 12V-48A/hr deep-cycle battery.

Now, I can get a DC-DC boost converter for $80, NBD.

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.

 

[John Fields]

On Wed, 12 Jan 2011 21:57:58 -0600, Guntar Gunderson <foo@fee.com>
wrote:

I have a simple heating circuit that takes 16V @ 3.5A. I want to run
it on a 12V-48A/hr deep-cycle battery.

Now, I can get a DC-DC boost converter for $80, NBD.

What will happen (generally) if I hook it up to the 12 volt source?

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

It doesn't have any solid state circuits... it's simply a resistance
device; I don't expect it to burst into flames. Am I violating any
basic safety rules if I plug into a lower voltage?

---
Not if what it's heating doesn't care about the lower temp.


View in Courier:
-+
E 16V |
R = --- = ------ ~ 4.57 ohms |
I 3.5A |
|
3.5A--> > 16V case
16V--[4.57R]--GND |
|
|
P = IE = 3.5A * 16.V = 56 watts |
-+

-+
E 12V |
I = --- = ------- ~ 2.63 amperes |
R 4.57R |
|
2.63A--> > 12V case
12V--[4.57R]--gnd |
|
|
P = IE = 2.63A * 12V = 31.56 watts |
-+

With 16V in, then, you'll get about 56 watts out of the heater, and
with 12V in you'll get about 32 watts.

That means that with 12V into it it'll get about 32/56 ~ 57% as hot as
it would with 16 V across it.

---
JF

 

[Rich Grise]

Jasen Betts wrote:

On 2011-01-13, Rich Grise <richg@example.net.invalid> wrote:
Guntar Gunderson wrote:

be exaggerated, because nichrome has some insane tempco of resistance.

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.

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

Thanks!
Rich

 

[Phil Allison]

"Rich Grise is off his Drugs":

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.

** Ni-Chrome has a large tempco ??

News to everyone that has ever used any.

Wot a moron.


..... Phil

 

[Phil Allison]

"Rich Grise"

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

** 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

 

[Rich Grise]

Phil Allison wrote:

"Rich Grise"

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

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.

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

Thanks,
Rich

 

[George Herold]

On Jan 14, 1:25 am, "Phil Allison" <phi...@tpg.com.au> wrote:

"Rich Grise"



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

** 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

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.

 

[Phil Allison]

"Rich Grise"

Phil Allison wrote:
"Rich Grise"

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

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.

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

** 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

Thanks,
Rich

 

[Rich Grise]

Phil Allison wrote:

"Rich Grise"
Phil Allison wrote:
"Rich Grise"

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

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.

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

** 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."

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

 

[Phil Allison]

"Rich Grise is a Fucking MORON "

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

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.

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

** 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."

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."

** And that is where you made the second error - fuckhed.

Now you've made a third and forth time just to prove how thick you are.




...... Phil

 

[Rich Grise]

Phil Allison wrote:

** And that is where you made the second error - fuckhed.

You can't insult me if you can't even spell "fuckhead."

Please go take your meds.

Thanks,
Rich

 

[Phil Allison]

"Rich Grise is a Fucking MORON "

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

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.

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

** 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."

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."

** And that is where you made the second error - fuckhead.

Now you've made it a third and forth time just to prove how thick you are.

Thick - like two short planks.




...... Phil

 

[Michael Robinson]

"Guntar Gunderson" <foo@fee.com> wrote in message
news:gltsi6tro7pplutg4rhtrcl0f46ptjo0v2@4ax.com...

I have a simple heating circuit that takes 16V @ 3.5A. I want to run
it on a 12V-48A/hr deep-cycle battery.

Now, I can get a DC-DC boost converter for $80, NBD.

What will happen (generally) if I hook it up to the 12 volt source?
It doesn't have any solid state circuits... it's simply a resistance
device; I don't expect it to burst into flames. Am I violating any
basic safety rules if I plug into a lower voltage?

Gunz

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!