# hair dryers and ceramic heaters



## dtbaker (Jan 5, 2008)

evmetro said:


> I have been reading about these heaters on this site with interest. Can you hook these up directly to dc traction pack power, or do you need ac power? I will be running 34 gbs 200 cells for 108 volts.



you can use ceramic heater cores at pack voltage.... you need a big fat contactor or SSR to turn them on and off. I used the fan 'on' power for the signal so that the heater would never come on without fan.

I have a whole section on my website if you go poke around.


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## evmetro (Apr 9, 2012)

Thanks for the input. I am converting a metro as well, so your site was fun. Sounds like the ac heater is ok to run off of dc.. nice. 12v fan power to contacter to traction pack.


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## evmetro (Apr 9, 2012)

Ok, so I picked up a ceramic heater at home depot for 22 bucks, and got the element out. It sounds like it is ok to power it with dc, but my question here, is how effective it will be. My main pack is 34 200ah gbs gen 3's. My gut feeling is that it will not perform as well as it would if I plugged it in an ac outlet in my house. Anybody know how this 1500 watt ac element will perform wired to this pack? Should I add a second element? My heater contactor is big enough to run a controller, so It will support as many elements as needed, I just don't want to dig into my range too deep...


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## subcooledheatpump (Mar 5, 2012)

How well it performs depends on how large of an area you are trying to heat

what car are you using it in?

If it's a smaller car it might be okay. 

If you have a mid sized car, then I'd say try using two of the 1.5 kW heaters in parallel. 

I take it you have a vacuum contactor, or as you say, one big enough for the main controller. You should be okay switching that much current then. 

Ceramic heaters are also self limiting devices, just in case you do have any fan issues, their temperature won't increase beyond a preset limit.


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## evmetro (Apr 9, 2012)

This is a metro. I am fabbing a heater core simulation with the element built in. Northern Ca climate... contactor is either a lev 200 or ev 200. I ordered it on the phone and don't remember which one. Should be here tomorrow.


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## mora (Nov 11, 2009)

Go and get another heater element and wire it in parallel. I had 30 cells (96V) in my pack and four of those 110V 1500W heaters wired in parallel. Two of them on at the same time was barely enough, four was okay. Less than half rated power anyway. I added more cells to my pack (144V) and now heat is good no matter outside temperature. Each element runs very close to 1500W.

You could switch both elements individually in case you don't want lots of heat and want to reduce amp draw.


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## mk4gti (May 6, 2011)

I tried running with one 1500w and it wasn't enough to get the cabin lukewarm. Get two in or plumb in a water heater.


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## tomofreno (Mar 3, 2009)

I also installed ceramic heaters in a metro, well a Suzuki Swift. Some details here:
http://www.diyelectriccar.com/forums/showpost.php?p=203777&postcount=599
At mid 20's F ambient I need to leave the heater on roughly 2/3 of the time to stay warm while traveling at 55-60 mph, less if going slower. I think that is due to air leaks around the doors (I know there are none in the firewall). I plan to try adding some weather stripping this year to see if I can improve it. On a sunny day, with ambient around mid 30's F or above I don't use the heater much at all, sun is enough. Of course, that depends on how you dress. In northern CA I would guess maybe one heater core would be enough, but the added cost of another is small, labor the same, and you already have a contactor that can handle the current, so I would install 2 in parallel, and bring all wires outside the heater box so you can access them easily to re-arrange connections if you want. I would wire it so you can power just some of the elements in each heater (check the connections for the "low" setting), or all of them for "high", but that requires an additional contactor. You also get much better air flow with two cores, which helps a lot.


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## dtbaker (Jan 5, 2008)

evmetro said:


> This is a metro. I am fabbing a heater core simulation with the element built in. Northern Ca climate... .


I suggest two. I have one element, and it is barely enough. If you have you dash pulled apart go for the stock heater core space, or consider one of the 3000 watt fluid heaters using the stock core (more expensive).

I didn't want to pull dash apart, and put heater in-line between the fan and divertor box. My setup is on my site.


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## evmetro (Apr 9, 2012)

Thanks folks for the input. I have the dash out and EVERYTHING out of the car, so this is a great time to get it right. The amount of additional time to up the number of elements is trivial at this point.


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## dtbaker (Jan 5, 2008)

evmetro said:


> Thanks folks for the input. I have the dash out


...ick. I went to great lengths to avoid pulling the dash. Could have made a few things easier/nicer like using the stock heater core area, and perhaps replacing gas gauge with EVdisplay behind the stock display... and fixing my silly fan control which only has off and full blast.

how long do you think it took for you to pull dash? I started, and it was looking like a full 4+ hour job to me...


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## Jamie EV (Oct 3, 2012)

dtbaker said:


> I suggest two. I have one element, and it is barely enough. If you have you dash pulled apart go for the stock heater core space, or consider one of the 3000 watt fluid heaters using the stock core (more expensive).
> 
> I didn't want to pull dash apart, and put heater in-line between the fan and divertor box. My setup is on my site.



Maybe this is a dumb question but what are your winters like? I'm in Ontario Canada. We get -40 sometimes lol.


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## dtbaker (Jan 5, 2008)

Jamie EV said:


> Maybe this is a dumb question but what are your winters like? I'm in Ontario Canada. We get -40 sometimes lol.


santa fe is pretty mild temp-wise. we're at 7000 ft, so we get snow and freezing.... maybe 10 storms/winter in town. Nightimes drop to 15-20 deg f, with maybe a week or two in the 0-10 deg f. But, then we have 310+ days of sun and winter days commonly rise above freezing.

so.... need for heat is minimal with an EV kept in the garage overnight. Need enough for defrosting and driving around in the occasional snowstorm, but not super insulated battery boxes w/ heaters.


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## evmetro (Apr 9, 2012)

Dtbaker, the dash takes two or three hours to pull, but it is really easy in a metro. You do not need to pull the dash to fix your fan speeds. The fan switch takes 10 minutes to remove, and is notorious for failing. Once it is out, you will find that the switch housing is coming apart. Zip tie or glue it back tight and reinstall. It will feel lile new again and you will feel all the detents again. Total time is half hour, total cost is near free


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## dtbaker (Jan 5, 2008)

evmetro said:


> Dtbaker, the dash takes two or three hours to pull, but it is really easy in a metro. You do not need to pull the dash to fix your fan speeds. The fan switch takes 10 minutes to remove, and is notorious for failing. Once it is out, you will find that the switch housing is coming apart. Zip tie or glue it back tight and reinstall. It will feel lile new again and you will feel all the detents again. Total time is half hour, total cost is near free



ooohhh, thats the best news of the day.... I just never took a real close look and been busy with other things; now I'll go back and see if I can pop that front off and go in laproscopically!  I'd really like to have the fan work at low speed and not just full blast.


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## Jamie EV (Oct 3, 2012)

well hell, 1500 watts should heat up a car like a sonofabitch man! I can't believe you have to double them up.


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## subcooledheatpump (Mar 5, 2012)

Consider the interior of the car may need to be 80 or 90F to melt ice on the windshield when the outside could be below zero. Not an easy task. 

For example, the Tesla Roadster uses a 4kW ceramic heater. Not a very big car, but a relatively big heater.


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## evmetro (Apr 9, 2012)

I picked up one more heater from home depot. Two of these fit nicely where the heater core was.


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## jeremyjs (Sep 22, 2010)

Jamie EV said:


> well hell, 1500 watts should heat up a car like a sonofabitch man! I can't believe you have to double them up.


It depends on pack voltage. On a lower voltage pack you won't get full rated heat output. You need DC voltage close to 150 to get the full 1500 watt rating that 120v AC gives you.


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## Jamie EV (Oct 3, 2012)

jeremyjs said:


> It depends on pack voltage. On a lower voltage pack you won't get full rated heat output. You need DC voltage close to 150 to get the full 1500 watt rating that 120v AC gives you.


Why would that be? Is there too much resistance? Cause I thought that was the point in this case...


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## tomofreno (Mar 3, 2009)

jeremyjs said:


> It depends on pack voltage. On a lower voltage pack you won't get full rated heat output. You need DC voltage close to 150 to get the full 1500 watt rating that 120v AC gives you.


 If you look at the link I gave in post #9 in this thread you can see this isn't necessarily correct. The two cores I used put out over 3100 Watt using my 36 cell, nominal 115V pack. There are different resistance heaters, and of course results depend on what resistance heater you use. KTA-EV sells different resistance cores for different pack voltages. If you scavenge a core from a ceramic heater like many of us, you get what you get.

1500 W isn't much for a car heater. Most ICE powered car heaters can put out way more, like over 4kw. If the car is well-insulated (most are not) and tight (most have air leaks), 1500 would likely work fairly well for temperatures above mid-20's F. My car has both leaks and poor insulation, so my first heater that put out only about 800W had almost no effect. At ambient temperatures of around 20 F, the heater blew out warmer, but cool air.

Edit: Roland, over on EVDL insulated the doors, floor, firewall and ceiling of the cab of his truck, made it air tight, and claims something around 600-800 W keeps it toasty in MT.


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## dtbaker (Jan 5, 2008)

while we're on the topic of ceramic heaters..... I'd love to revisit what people are using to turn them on and off. I used the ol'standby mechanical contactor kit with magnetic blowout available from kta. Looks like they have changed to offer an enclosed relay, with a diode, cap, and fuse for $80 or so.

What are YOU using, and how's it workin for ya? and at what pack voltage/heater rating?

... I'm asking because if I upgrade to 2 cores for 3000 watts or so, I think I need to upgrade my contactor.


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## mora (Nov 11, 2009)

I'm using two SSR (solid state relays). Two elements for each. I've burned at least 5 of them while experimenting. They also fail on. There might be differences in these relays but I'll share what I've experienced from cheap chinese stuff:

drive them at 13-14V or even higher if possible. On-resistance differs even between 12V and 13V. Higher drive voltage, lower on-resistance. SSR gets hot at 20A even if it was rated for 40A. 40A might be peak value it can stand. Heat sink is absolutely necessary. If SSR comes with heatsink you need to sand contact surface flat. Even then relay might fail after 60min of continous use at 20A load (I've tried, hehehe. It was one hot hour in car while heater was cranked up fully). I believe these relays will be fine if placed in path of cold airflow. Mine are inside center console but I don't care about their temps as I never sit in my car for over an hour. One could place thermal switch to heatsink to switch off the relay in case temperatures rise too much.


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## subcooledheatpump (Mar 5, 2012)

Ceramic Heaters are self adjusting and self limiting, to a certain extent. 

Even with a lower or higher voltage, they can still output full power without problems.

As for relays/contactors, I use a kilovac EV200. I'm running 4kW worth of finned strip heaters in my van on 340 volts DC. 

I've used ceramic heaters before on the same voltage, and more. They work, but 3 kW just wasn't doing it for me.


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## dtbaker (Jan 5, 2008)

subcooledheatpump said:


> As for relays/contactors, I use a kilovac EV200. I'm running 4kW worth of finned strip heaters in my van on 340 volts DC.


do you use diode/cap/resistor for soft-start? if so, please share specifics!


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## subcooledheatpump (Mar 5, 2012)

The contactor has a built in soft start PWM circuit for the coil, it also adjusts the coil voltage/current once pulled in. 

The heaters are connected directly to the battery pack,(via EV200) this pack is seperate from the pack that runs the motor


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## dtbaker (Jan 5, 2008)

subcooledheatpump said:


> The contactor has a built in soft start PWM circuit for the coil, it also adjusts the coil voltage/current once pulled in.


huh, thats nice. I didn't know that about the kilovacs! simpler is way better for people like me. 
...looked up spec sheet, and while the ev200 is obviously overkill for a 15-25amp load, it means it should last a LONG time make/break under relatively small load, right?



d


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## mora (Nov 11, 2009)

subcooledheatpump said:


> Even with a lower or higher voltage, they can still output full power without problems


Did you ever try your elements at lower voltage? Mine simply wouldn't sustain heat output at 96V and fan blowing at medium speed. Low speed was fine but if airflow was increased amps dropped. Element just cooled down. Single element didn't draw more than 10 amps at 96V either. 960W max power. 144V is whole another story. Element keeps the same temperature no matter blower setting. Even without any airflow they won't burn but I believe it isn't good for elements anyway. Amp draw was about the same, actually increased a little bit. But at 144V it is over 1400W. Real difference.


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## mora (Nov 11, 2009)

dtbaker said:


> ...looked up spec sheet, and while the ev200 is obviously overkill for a 15-25amp load, it means it should last a LONG time make/break under relatively small load, right?


Yes. Datasheet estimates 100k cycles (make/break 50A load at 120VDC). I should have got two kilovacs instead of box of chinese SSR in first place.


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## subcooledheatpump (Mar 5, 2012)

Yeah ceramic heaters are positive temperature coefficient. They use more as they heat up. As long as you get the airflow right they should be happy. 

I've tried a 240VAC ceramic heater on 120VAC and up to 600 Volts DC. Never had a problem and from my measurements, always got full power, given the right airflow/ temperature.


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## dladd (Jun 1, 2011)

dtbaker said:


> while we're on the topic of ceramic heaters..... I'd love to revisit what people are using to turn them on and off. I used the ol'standby mechanical contactor kit with magnetic blowout available from kta. Looks like they have changed to offer an enclosed relay, with a diode, cap, and fuse for $80 or so.
> 
> What are YOU using, and how's it workin for ya? and at what pack voltage/heater rating?
> 
> ... I'm asking because if I upgrade to 2 cores for 3000 watts or so, I think I need to upgrade my contactor.


Here's what I've got: The EV200 contactor behind the box provides pack voltage (153v nominal) to a 20a glass fuse (shown in front of the heater box) when the key turns on. Inside the box is a standard automotive relay that is triggered by the heater fan, so whenever the fan is running, the heater elements are on. That small relay then turns on the bigger relay which actually passes the pack voltage to the heater elements. I have two elements, one is run through a 20a switch so I can choose either one or two elements at any given time. I've never needed both, but I live in California and usually am in a garage overnight.

It was all installed by the original builder of my car, so I don't know all the details. Like, how big are the heating elements? Why is there the smaller relay that then powers the larger relay? What is the diode looking thing across the outputs of the large relay?

It works well, but when I want to be able to use the defroster without any heat I have to pull the fuse (that's how I've had it all summer long). 

Is this the same as the older style KTA kit you are using?


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## Jamie EV (Oct 3, 2012)

That's one hell of a contactor relay. Has anyone ever tried running the heater into the old heater core hoses in a closed loop and shunting some to the batt boxes for winter? Can you populate the core hoses with hot air instead of coolant? That would mean no ripping out the dash...and perhaps a different switch for the heater? Just a thought.


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## tomofreno (Mar 3, 2009)

dtbaker said:


> while we're on the topic of ceramic heaters..... I'd love to revisit what people are using to turn them on and off. I used the ol'standby mechanical contactor kit with magnetic blowout available from kta...


 I'm using the same P&B from kta, and these fuses:
http://www.ferrazshawmutsales.com/pdfs/A2DA6D.pdf
Purchased at Discount Fuse. Haven't blown these fuses and the contacts on the P&B look shiny-new. Current draw by the heaters is typically 25 - 27ADC. I typically let it run for about 10-15 minutes then shut it off for about 10 min. Been using the relay 3 winters, 2 with the current fuses and 3kW double core, so the relay has been exercised.

The resistance of ceramic heaters is typically U-shaped as a function of temperature. I measured resistance of one of the cores at room temperature and after turning the heater on as described in the link I gave in post#9 this thread, and it was significantly lower with the heater on. I then removed the fan I had placed on blocks over the heater core and the resistance increased.


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## evmetro (Apr 9, 2012)

Wow! Lots of great info on this thread. Does anybody know how hot these ceramic elements get? The home depot space heaters I got have the elements surrounded with plastic that touches the sides of the element... do I need to be concerned about melting nearby surfaces?


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## EVfun (Mar 14, 2010)

evmetro said:


> Wow! Lots of great info on this thread. Does anybody know how hot these ceramic elements get? The home depot space heaters I got have the elements surrounded with plastic that touches the sides of the element... do I need to be concerned about melting nearby surfaces?


Yes, but only slightly. There are a number of plastics that can withstand the heat. Generally, the heaters are left in their surrounding plastic frame. You will see when you pull the heater apart that the elements are snapped into a small plastic surround that is then attached to the rest of the heater. This frame gives you a non-conductive surface to attach them to your EV heater box. 

Ceramic heaters usually only get hot enough to lightly char newspaper. As their temperature rises above the design point the resistance of the ceramic elements increases and the current falls. I've done tests with the heater elements between 2 stacks of newspaper with no air flow and the current drops to a couple amps as the elements get hot. At normal temperatures the elements draw 12 to 15 amps.


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## swoozle (Nov 13, 2011)

EVfun said:


> Yes, but only slightly. There are a number of plastics that can withstand the heat. Generally, the heaters are left in their surrounding plastic frame. You will see when you pull the heater apart that the elements are snapped into a small plastic surround that is then attached to the rest of the heater. This frame gives you a non-conductive surface to attach them to your EV heater box.
> 
> Ceramic heaters usually only get hot enough to lightly char newspaper. As their temperature rises above the design point the resistance of the ceramic elements increases and the current falls. I've done tests with the heater elements between 2 stacks of newspaper with no air flow and the current drops to a couple amps as the elements get hot. At normal temperatures the elements draw 12 to 15 amps.


I'm working to install a couple of these PTC ceramic cores and have run into a snag. One of them is quite a bit different in terms of resistance than the other even though they are the same brand/style bought at the same time.

When I bench tested them in parallel with my 48 cell pack (155-160V usually) and some nominal air flow, they really wanted to be at 400F-450F. I'd rather they run a little cooler so I rearranged the wiring, still in parallel. That didn't change anything. Those suckers really want to be at their sweet spot temp.
So I tried putting them in series, thinking that halving the voltage drop across each would fix it. With all 5 of the wiring terminals in use for each, they STILL wanted to be at 400F. Those things have a hell of a resistance valley.

In further testing I have been able to get one in the 250F range but the other won't heat up enough (90F) to slide down into the valley, or conversely, one goes too hot while the other is reasonable.

I noticed that the room temp resistance was quite different when I bought them but didn't think much of it, knowing that the real action is when they have voltage applied. I'm going to go buy another and see if I can get one close to one or the other that I have.

450F seems a little hot for day to day operation. Does that make anyone else nervous? Or is that expected and I'm wasting my time?


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## EVfun (Mar 14, 2010)

I never did check actual temperature, only a paper char test. I would guess they elements where hitting 350F. I did observe quite a difference in cold resistance and poor reaction (big temperature differences) trying to run them on reduced voltage to limit heat levels.

What I ended up doing with my 2 element system was to make low the use of half the elements from each heater. My heaters had 5 tabs and where designed for 120 volts between 2 adjacent tabs. Trying to use 60 volts across elements resulted in vastly different heat levels from each unit (120 volts between the center and the outer 2 tabs.) What I ended up doing was to connect terminals 2 and 4 of each heater to pack negative. Then for low connect 1 and 5 to of each heater to pack positive using a KUEP-3D15-12 relay and for high also connected the center tabs (tab 3) to pack positive with another KUEP relay. I used heater fan power to drive the heater element relays so they heaters could not run unless the fan was running.


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