Apollo 13 inside my car !  or how to get lower AMP for a heater ?

Hi redgreenblue,

What you are trying to do will be difficult as you are fighting design. Since the heater is designed for 120 VAC @ 2.1 Amps this means that the effective resistance of the heater element is 57 Ohms. If you take a 57 ohm heater and power it with 12 volts we will have a current of 210 mA or just under a quarter of an Amp. This translates to 2.5 watts which will not provide any usable heat. One option would be to use an inverter but unfortunately this would demand at least 25 Amps from your 12 volt system. While you could wire the inverter directly to the battery and use it only when the car is running you would have the expense of an inverter. If you take any of these suggestion make sure you leave some tolerance . For example for a 250 Watt heater you would want an inverter that can handle 300 or 350 Watts as a safety factor. The motor is another question. If it is an induction motor then it must have AC to operate. Some of the better inverters will run an induction motor. You mentioned that the motor was DC. You may want to check and verify this as it is unusual for the manufacturers to put additional expense into these small heaters. If they have AC voltage available for the heater element they likely are also using the same for the motor.

Correction: I was too quick. Your motor is 12 volts. That leaves you with only the problem of how to convert a 120 volt heating element to a 12 volt one.

It may be better to just buy a heater that is designed for 12 volts. Here is a small 600 BTU/Hr 12 volt 15 Amp model that mounts on a visor.

https://www.walmart.com/ip/Roadworthy-THR6000C-12-Volt-Auto-Heater/47651732

In my opinion the cost to use an inverter to run the small AC heater would be impractical. Converting the AC heater for use in the car will be impractical also.  Sorry.

John

Hi,

thanks for the advices.

Before buying this heater I actually bought the same 12 volt 15 amp model you send. Unfortunatly that thing does not give heat as it should but the main problem is it stop to work after 2 times, so my opinion is this is not a reliable solution. You can also check on youtube you'll see that most peoples who also baught this kind of small heater didn't have what they expected. I don't want to be rude, it's simply did not convinced me. Been on the problem for a while now.... so I kinda look everywhere for solutions.

I've already got the inverter, it's a 400 watt. I purchased this one becuz it's the closest to 250 watt so the less expensive...for the needs.

Also I changed the fuse on the lighter port from my car to 30 amp expecting to be letting more AMP to the lighter but it didn't.

Anyway, so I got 2 choices now, according to what you said

Hook the inverter directly to the car battery or buy another battery that I'll use only for that.

Still I wonder why the 'switch is able to make the heater go from 250 watt at 'LOW' and then to 460 watt at 'HIGH'" I don't know if you seen the pictures but I'm wondering if the switch is responsable for the 'AMP' switch or only the 'voltage ?

thanks John !!

Hi Sorry

I didn't look at the pictures before I wrote the first time. I have looked now and so I hopefully won't have a red face this time. The heater actually has (2) heaters that can be hooked up together to create the high and only one to create the low. From what I can see each heater is designed to handle 120 volts and put out 1/2 of the max output of the heater. Your inverter should work with this unit but it may have to have heavier wires running to the battery. If you put in a bigger fuse but don't change the wires the wires could over heat and start a car fire. Based on your original 250 watt rating of the heater I would expect the inverter to draw 25 Amps when it is running the heater. If you have the inverter inside the car you will at least capture what ever heat it is also producing.

I am sorry that the visor heater didn't work. unfortunately there is a lot of poor quality stuff out there.

John

I will bother you one more time. You mentioned that the heater is at 460 Watts when it is on high in the last posting. At 460 watts the heater would draw about 40 amps from the 12 volts. This would also exceed the rating of the inverter. If an inverter detects an over load of this nature most will just shut down and refuse to work. You had a question about Amps and volts. In your case you  have 12 volts. Depending on the resistance of the item that you attach to the 12 volts a current will flow. The wattage of a load is determined by the voltage across it multiplied by the current that it is drawing from the power source. The only way to change the current flow from a fixed voltage like 12 volts is to change the resistance of the load. Since the resistance of the ceramic heaters are fixed we don't have anyway to change the load.  You may want to begin with the heater on the low setting so you don't overload the inverter or the vehicles wiring. Also keep in mind that this type of load on a 70 Ah car battery will more or less drain it below start level in an hour or so. Sorry I don't have a more upbeat fix for you.

John

Alright,

Now I understand probably why I coudn't find an easy solution on that... Like you expected, at 'high' level on the heater, the inverter shot down, I tried this option to see what it would do...also drain out the 30aH battery I had to test the whole thing.

There just one thing that bother me, it's that I don't understand how the heater is 'fixed' by a resistance ?

And why changing this resistance won't work ?  Why this don't work like a regular resitance ?

Maybe something I didn't understand here...anyway forget it.

still very cold I'll need to use a fuel heater even if this sound totally crazy.

c ya

redgreenblue  wrote:

 

. . . . still very cold I'll need to use a fuel heater even if this sound totally crazy.

 

 

Not crazy at all! Eberspächer have been around for decades!

Hi Andrew,

The heater element itself is the resistance. If we could get inside and tap onto the resistance wire 1/10 of the way down then we would have the proper resistance for 12 volts which is 1/10th of 120 volts. The other option would be another ceramic heater that was built to have the proper resistance for 12 volts. Heat is a very difficult energy form to obtain from the electrical system in a car. The relatively low 12 volt system demands low resistance and high current in order to generate the sufficient amounts of heat needed for our comfort and to compensate for the relatively poor insulation afforded by the cars design and large glass surface area.

I personally would drive cold and with lots of clothes or even not drive before I would drive with a fuel type heater in the enclosed space of a vehicle. Fuel heaters quickly consume the oxygen levels in an enclosed environment and then they produce carbon monoxide which will silently and odorlessly kill you over time. The effects can be accumulative if adequate time is not left between exposure. There has to be a better solution than using a fuel heater.

Good luck

John

Hi John,

The linked heaters are mounted in the engine bay nowadays.

I think the old units from the VW campers were cab mounted but - for your stated safety reasons - I guess that’s why they moved them.

OK I feel better. Just didn't want to loose a friend to CO.

John

Amen to that, death by a shonky setup is never good!