[Hatchita]

I've been reading many of your posts about the ceramic heater elements and how you guys installed them. But I have a few questions.

I bought a ceramic heater off the shelf, got the element out. It's 1,500 watts element with 4 rows of ceramic elements (375 watts ea) and 4 actual ceramics on each row (93.75 watts ea):



On the side it says it's rated for 120 V / 60Hz / 1500 W.

So question #1 is, these things don't heat up with DC? It has to be AC?

My second question is, even tho it design for 120v, but can it work on a different voltage? a smaller voltage maybe? What will be the difference, will it draw more amps if I operate the element ant a lower voltage?

Thanks in advance...

[rillip3]

It will heat up on DC. It may or may not reach the temperature the AC voltage gave it, but it will provide heat.

It will work on smaller voltages, but smaller voltage = smaller heat. The way a heater works is it is basically one huge resistor. The only difference between it and a traditional resistor is that it's designed to dissipate the heat quickly (so you feel it instead). I would want to test it to be sure, but as far as I know, it will draw more current on 12v than it would on 120, but it will not pull an equivalent power. Sya it pulls 2A @ 120v, I do not think it will try to pull 20 A @ 12v. It will pull a higher amp draw, but it will just stop heating up at some point. You won't be happy with it at 12v, undervolting it that much will lead to very poor heating. If you wanted to run it at, say, 96v, or something close to 120, it will heat up close to what you would expect.

[Hatchita]

Thanks rillip3,

I attached a 12v fan and connected the test rig to a 12v battery. I wired only one of the 4 resistor rows, and tested voltage was present between the aluminum fins that sandwich the ceramics. In theory it should heat "something". But it was cool to the touch. It seems the 12v are just not enough to get it running:

Youtube test here

I'm on my way to the local surplus store. I'm sure I can get a 12v to 120v transformer. I'm only concern about picking one too small that could get ruined with the amperage draw.

Will post results later.

[rillip3]

why not just attach this to the traction pack rather than the accessory?

[EVfun]

Originally Posted by Hatchita

I'm on my way to the local surplus store. I'm sure I can get a 12v to 120v transformer. I'm only concern about picking one too small that could get ruined with the amperage draw.

Uh, transformers don't work on DC!

[Hatchita]

Originally Posted by EVfun

Uh, transformers don't work on DC!

Oh snap... forgot that.... back to the drawing board.

[ElectriCar]

It will work on pack voltage but not 12VDC. Mine runs on 144V and cranks out 2100 watts! But to get the most heat out of it, you have to blow a lot of air through it. Ceramic heaters will not allow you to blow them up by over voltage as I understand it. As they heat up, the resistance increases so it will limit the current increase as it warms up.

[tomofreno]

Just for info, I bought two of these same heaters at Lowes recently (same color wiring, connectors, etc). I measured about 12A with it plugged into the wall at 122VAC and set on high, so about 1460W - after temperature stabilized. That is the complete original heater, just pulled out of the box and plugged in. Electriccar's higher voltage puts more current through it at a given resistance, so quite a bit more heat since it goes up with current squared. My pack is only 115V nominal (36 cells), so I expect to only get maybe 1300W or so out of one. But my original core was 7 1/4" wide, so I have made a custom mount to fit two of these side by side in place of the original core (they are 3.5" wide, 3.87" along the dimension the terminals are on). Hoping to get 2600W out of them, and maybe a bit more with the larger blower in the car.

Hatchita, don't know what you paid, I only paid $21 each, for that price you could just sit two in the back of the car and power each with an inverter. They are wired so all 4 of the ceramic elements are in parallel, but you can't supply enough current to drive 4 in parallel with a 750W inverter and get much heat, but two heaters wired with current through just one (as you did) or two ceramic elements should be enough heat to keep their little feet warm.

[EVfun]

I found some at my local Ace for about $20 that had 2 separate smaller elements. They where the same length, but each unit had 2 rows of ceramic with 3 connection tabs. My idea was to make 2 little heater boxed only about 2 inches tall and place one under each front seat. They could suck air in the back and blow out the front. It would provide a source of recirculating heat. Heating fresh air is important for defrosting, but a little recirculating heat warms the cab up faster when it is below freezing. I recommend 2, "1500 watt" ceramic heating units for a passenger car EV, but my heater box only has room for a one (the stock heater core was a little square thing that was 4 rows thick.)

[jimca007]

The formula you need is power = volts * amps ( P=IV)
so
1500/120 is the current ( 12.5 amps )

1500/12 would be 125 amps to maintain the power output you had at 120v when using a 12 v supply

not really do -able so using your inverter to boost to 120v again is the best bet but you'd need a 1.5kw inverter to power all the elements