# Ceramic Heater and 160VDC?



## gdirwin (Apr 7, 2009)

Ceramic heaters are meant for 120V RMS (or 240V RMS), but what about in-between voltages? I hope to use 160VDC for my pack voltage - how will a 120V ceramic heater work?

I know they have an "inverse resistance" characteristic, which hopefully will increase the resistance as it gets hotter... It is the RMS value of an AC waveform which dominates its energy rating (ie thermal heating capacity) not the peak voltage (which would be 169.7V).

Anyone used 160V (or higher) and a 120V ceramic heater?


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## ZEVUtah (Apr 10, 2008)

Do you have room for 2 heater elements. If you can use two then wire them in series and each of them would use half of your voltage right? 

KJD


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## Overlander23 (Jun 15, 2009)

Most of the $20 consumer ceramic heaters have two heat settings which is accomplished by switching elements in parallel, 750W or 1500W. If you run these in series you'd cut the voltage in half... you wouldn't need another ceramic heater.

I believe Etischer has some experience with this. His ceramic cores had four circuits... originally switched in pairs in its original life as a room heater. In his EV he ran two pairs in series for his 320v system.

http://www.diyelectriccar.com/forum...-passat-37316.html?&highlight=etischer+heater


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## gdirwin (Apr 7, 2009)

Thanks for the replies - the problem with using elements in series is that you get either 120V or 240V rated voltages - 160V is in the middle. The power (Watts) is a function of the voltage squared (assuming a constant resistance).

Applying 160VDC to all 4 elements in parallel (120V rated each) the heater would absorb 1500 W * (160/120) * (160/120) = 2667 Watts (or 178% of the rating).

Applying 160VDC to 2 parallel strings (with 2 120V series elements per string) the heater would absorb 1500 W * (160/240) * (160/240) = 667 Watts (44.4% of the rating).

Too much or too little.




My hope lies on the inverse resistance effect in these ceramic heaters. The "barium titanate" material is unique in that its resistance increases as the temperature increases. In other words, if you apply a higher voltage, they will get very hot very quickly, but then the current will reduce (resistance increases) as the temperature rises above some level...

I believe Etischer is planning a 320VDC build with 230VAC rated elements (similar problem - maybe even a bit worse!) but so far has only tested with a 230VAC supply...

I am still not sure if this is a big problem or not... Anyone else used 144 or 160VDC with a 120V element? Trying to avoid magic smoke...


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## ZEVUtah (Apr 10, 2008)

You might want to talk to Randy at Canadian EV. Heating would be more of an issue up his way. 

http://www.canev.com/KitsComp/Components/Heater.html

It seems like I read that the elements rated at 144 volts could be used at 156 and they were OK. Not sure if 160 volts would push them over the top or not.


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