Frost Fighter wind shield wiper deicer grid

[oil pan 4]

This is where I try to install the Frost Fighter wind shield wiper area defrost grid before the next big winter storm.
Problem is frost fighter doesn't make a wind shield deicer for passenger vehicles. The setup uses 8 grids about 6 inches wide and it has to be between 68 and 83 inches.
Problem is I only need about 60 inches and 4 grids.

Needless to say I will be going off book for this one.

Originally posted here down near the bottom of the page:
http://ecomodder.com/forum/showthrea...a-32503-5.html

[spacemanspif]

Can't wait to see how it works.

Could you cut down the middle of the lines, stick the lines where you want and then use a repair kit to join the 2 halves? I've used the kits where lines have broken and it has always worked well for me. I assume cutting 2 lines off the top won't affect the functionality of the grid?

[oil pan 4]

I am just going to apply them as instructed, just shorter runs of lines and fewer of them and provide my own power source.

Using shorter runs or fewer lines will how no effect on the functionality of the grid its self at all. Problem is the provided power/time controller will not work. If I try to use the provided power/time controller it will fry the grid or its self.

I was not sure how much power to apply. Then I realized they spelled it out very clearly in the technical specifications. For the 83 inch install using all 8 grid lines the books says it should use 16 amps. So I know length, amps and volts that is more information than I need. I end up getting a total power dissipation of 0.3 watts per inch of grid.
With the short install of 68 inches and 20 amps I get 0.44 watts per inch.
So any where between those two watt/inch numbers should be good.

Now I plan to use about 60 inches and 4 grids.
If I want to get 0.3 watts per inch then I will need to limit power to the grids at 6 amps on the low end.
Then on the high end, 0.44 watts per inch I want to limit power to 8.8 amps.
I have a feeling that 6 amps will be plenty.

The other good thing about using half the grids is that gives me more grids to put some where else. But I will have to buy another pair of grid bases. Grid bases are the sticky thing that the grid ends attach to and get their power from, also where you hook up the power.
I am thinking with the other 4 grids I will just run them the down the length of the passenger side rear glass. That way I can see my blind spot when I am in the left lane when its icy or when the window is frosty.

[oil pan 4]

Alright, it does not work with the resistor. All it did was heat up the resistor real good. With the resistor the frost was perfectly comfortable sitting on the resistor grid lines them selves.
I wired it straight up to power, it was drawing 9.5 amps.
That melted the frost.
I think what I will do is make a High and low switch. The works because all I had was an On-off-on switch.
To regulate power down to the deicer I think I will need a PWM.

[Joggernot]

I thought rear window defrosters took 25 amps to work. You might be going too light in the amp department.

[oil pan 4]

This is a fraction of the size of a rear window defroster.
If it draws 10 amps it will eventually burn up the grids.

This is what happened this morning:
I called the Planned Products LLC (the frost fighter company) to order more little parts to I can use the left over grid to put a defroster on the passenger side rear glass of my suburban.

I told them I chopped up their system and put it in a passenger vehicle.
Their response was because I was calling to order parts.
Apparently these grids will burn up if you run them for extended time with no current limiting. They always get calls when this happens.
So don't do that.
Apparently there is a fine line between disaster and success. These grids hooked up to straight vehicle power with no current limiting, a 1.3 ohm grid on 14 volts would draw around 10.8 amps. According to their specifications I should limit my grid to 8.8 amps (0.44 watts per absolute inch of grid line).
Adding the 0.3ohm resistor to the grid with battery voltage at 12 volts will limit amps to 7.5, running it at 14 volts, engine on will limit it to 8.8 amps.
So according to the frost fighter parts/tech support people the extra 2 amps you get form no current limiting is enough to fry it.

Then when I told them I used their technical specifications to calculate the amount of wattage needed per inch of grid then scaled it down to my application they were pretty surprised, they have never seen any one do that.

$15 for parts plus shipping got me enough bits and pieces to use up the rest of the grid on my suburban side glass.


Here is where I believe most people go wrong when they go off book. They look at the rear defroster and see the grids go straight across and copy that. These grid lines are too thick to do that.
Just wiring these grids straight across is a recipe for disaster.
You want to double the distance the current has to travel.



I am thinking I would like to retain use of the incorrect configuration, where power is wired straight to the grids.
Put it on a ToF relay, a time to off relay and set it so it can only draw full power for maybe 20 or 30 seconds then the relay times out and switches power through the resistor.
The High setting would likely be used for snow and blizzard conditions like what we had here last weekend.
(so much for man made globul warming soon making snowy winters a thing of the past)

[oil pan 4]

Tried out the 0.3 ohm resistor. It was showing 8.5 amps on battery power only.
It was slower to melt the frost, compared to no resistor.
With the voltage drop after the resistor, with alternator power should be very close to my grid watt/inch target.

Next time I have some time off, some time next week I want to put the grids on the side window and regulate power with a PWM. Should be sometime next week.

The additional parts I ordered from Planned Products LLC (the frost fighter company) should be here any day now.

[pletby]

Watching with interest. Nothing worse than a half frozen windshield in a heavy snowstorm where half your vision is obscured by heavy melting snow streaked because of iced up wipers and a frozen top half of windshield, while others around you can't see either.

What is a PWM?

[oil pan 4]

The PWM is short of Pulse Width Modulator.
It controls power like resistor but with almost none of the resistor heating losses.