Ski boot heater blowing fuses

Thread Starter

GFK1984

Joined Dec 9, 2022
4
Hello,
I recenty assembled a pair of ski boot heaters to plug into a 12v socket in my truck. I am not an electrical engineer or designer, but the concept seemed simple enough: I used two 12v RV water heater strips (silicon strips) wrapped around aluminum flexible conduit with a heat shrink wrap. These are wired in parallel, and draw 150 watts each and routinely blow the 20 amp and lessor fuses in other vehicles. Using an online calculator, it appears that my device is drawing about 25 amps, hence the fuse problem. I beleve that I can reduce the amperage drawn using a resistor, but I dont know how to size or source one that would work. Can anyone help me out?

Thanks.
 

dl324

Joined Mar 30, 2015
15,439
Welcome to AAC!
I beleve that I can reduce the amperage drawn using a resistor, but I dont know how to size or source one that would work. Can anyone help me out?
Putting the elements on separate circuits isn't an option?

How long can your battery/charging system tolerate a 25A load?
 

Thread Starter

GFK1984

Joined Dec 9, 2022
4
I only use the warmer when I am driving up, so there doesnt seem to be an issue with draining the battery and I have not seen any issues with the alternator. I actually installed a 30 amp fuse in my truck, so it works fine. But when I share a ride with others, I blow thier accessory fuses:). I do have two accessory outlets, but I am not sure they are fused separetly. Operationally, a single 15-20 amp connection would be best. The heater is plenty hot so its ok if it runs cooler.
 

KeithWalker

Joined Jul 10, 2017
2,609
Hello,
I recenty assembled a pair of ski boot heaters to plug into a 12v socket in my truck. I am not an electrical engineer or designer, but the concept seemed simple enough: I used two 12v RV water heater strips (silicon strips) wrapped around aluminum flexible conduit with a heat shrink wrap. These are wired in parallel, and draw 150 watts each and routinely blow the 20 amp and lessor fuses in other vehicles. Using an online calculator, it appears that my device is drawing about 25 amps, hence the fuse problem. I beleve that I can reduce the amperage drawn using a resistor, but I dont know how to size or source one that would work. Can anyone help me out?

Thanks.
150W in each boot is enough to cook your feet in a very short time. If you wired them in series, they would only draw a total of about 6A and you would still have 37.5 watts per boot. The soldering iron I use regularly is 40W and it runs at 300 deg. C,
 

Thread Starter

GFK1984

Joined Dec 9, 2022
4
I thought of that, but wouldnt I have to cut into the end of one of the silicon heating elements and find wires to connect into? Just not sure whats in there, or how easy it would be to find the right wires. Also, these heaters are to warm-up the boots before putting them on- softens the shell so they are easier to push into when its cold out.
 

KeithWalker

Joined Jul 10, 2017
2,609
I thought of that, but wouldnt I have to cut into the end of one of the silicon heating elements and find wires to connect into? Just not sure whats in there, or how easy it would be to find the right wires. Also, these heaters are to warm-up the boots before putting them on- softens the shell so they are easier to push into when its cold out.
Were the heating elements already connected in parallel when you got them? If not, there will be just two wires coming out of each element. Take a wire from each and connect them together. Apply the power between the other two wires.
 

SamR

Joined Mar 19, 2019
4,484
Simply putting a 30A fuse in so it won't blow is a very bad idea... The fuse is there to protect the wiring from burning out in case of a short and increasing the fuse amperage defeats that purpose and can lead to a fire in the wiring harness!
 
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