So I was conducting a few experiments related to thermal imaging with an infrared camera at university the other day and thought it would be interesting to measure the output of a standard set of aftermarket ATV/snowmobile/motorcycle grip heaters (hand warmers). It turns out that they get a lot hotter than I imagined they would and I learned a few things I'd like to share. First I'll go through the tests I did and then I'll draw a couple conclusions. The grip heaters that I tested were manufactured by Kimpex, part number 912025, a kit that Kimpex recently replaced with part number 12-170. They can be seen in the link below: http://www.kpx-kimpex.com/catalog.php?action=nav&page=942&show=1 To power the grip heaters, I used a 12V motorcycle battery that is rated at 8Ah. This means that the battery could run a current of 8 amps at 12 volts for 1 hour (well theoretically anyway). Here's the initial setup connecting just one heater element up to the battery to measure it's temperature: I used a thermal imaging camera system owned by the university. It has a camera on a tripod, hooked up to a computer and monitor as shown below. The easiest way for me to share the thermal images with you is to just take a picture of the computer screen with my digital camera. Here's what the heater element looks like to the camera with the camera at a distance of about 6 feet from the heater element: As you can see, the heater element is quite hot. There are 3 smaller plus signs or markers on the screen with numbers beside them. These numbers correspond to the three temperature readings displayed at the upper left of the screen. There is an adjustable temperature/color scale on the right of the screen. Marker # 3 indicates that the heater element is at 89 C (192 F). This is not quite the actual temperature of the element because the camera is also measuring the temperature of the air between it and the heater element. The closer the camera is placed to the element, the hotter the element appears, but the difference is not that great, so I just left the distance at that. So 89 C that’s pretty hot right ? Well, turns out things get hotter. That temperature is in free air with the element exposed to convection losses into the room and conduction losses into the cool cinderblock wall (18.39 C). I changed things up by adding another element (the kit comes with two). Both elements are connected in parallel as the manufacturer’s instructions indicate, but I did not use the low heat setting resistor included in the kit. This resistor soaks up a voltage drop, so the grip heater elements don’t see the full 12V. I was interested in the max output, so I didn’t bother with them. I also used an adjustable power source instead of draining my motorcycle battery. Here’s the power source. I adjusted it to put out 12V DC. The two heater elements connected in parallel drew 2.32 A. This means that since the voltage across them was 12 V, then the power they are consuming is: P = V*I = (12 V)*(2.32 A) = 27.84 W So they are sucking up almost 28 watts of power. My XL600R bike has a Ricky Stator that puts out 200 W, and I think ½ of that is for lighting and accessories (but I’m not 100% sure of that). So since my headlight is 55 W and the tail light is much less than that, I think there would be no problem running the grip heaters. I placed the two grip heaters (connected in parallel) inside a tin box to attempt to contain the heat. The idea was to create a controlled volume, to raise the specific heat. I wrapped insulation around the box as well as placed some in the bottom of it to try to contain the heat. I wanted all (or as much as I could get) of the heat to exit through one surface – the top. Then I put the lid on the tin box. Then I changed the setup to measure from above, since heat rises that would be the best direction to measure the output. Then I turned everything on and began recording the temperature. The temperature of the tin box lid climbed in a sort of logarithmic curve from room temperature (around 24 C) to a steady state temperature of 52 C after about 20 minutes. This is quite warm (or hot depending on your perspective) to the touch. I watched it for an hour and the temperature remained at 52 C. So I thought that was a pretty good approximation of the sort of heat escaping through the box lid area. I’ll save the heat transfer calculations for another day. Then I was curious as to how hot it was inside the tin box, so I lifted the lid. And holy cow, it was hot in there. By the time I was able to take a picture the temperature had dropped to 122.5 C (253 F), but was slightly higher than that the instant after I removed the lid. I think it was just over 130 C. So, yikes, those little buggers get hot! I also did a test where I placed both heater elements into the tin box, sandwiched between layers of insulation, so that there was insulation above and below each element and there was no air space in the box. As some of you might predict, this did not turn out good. The outside of the can remained somewhat cool, while each element was getting right hot. I took the lid off to see what was going on and the elements were smoking. The element backing had begun to melt and become delaminated. Good thing I stopped when I did. Here’s what the elements looked like after that little disaster. So what to take away from this business? Well first off, the elements get right hot! Also, because of this, they need a heat sink to keep from melting your hands. This is usually a steel or aluminum handlebar. This explains why when you use this type of grip heaters on a motorcycle, the right (throttle) side is much hotter than the left side. The plastic throttle tube insulates the grip heater element from direct contact with the handlebar, so there is not good of a thermal conductivity or heat transfer from the element to the bar. How to correct this? I don’t know. But I am guessing that if you could put the elements inside the bar on both sides, then the bar would get even heat on both sides, but your right hand would still be shielded from the bar by the throttle tube, so now it would be the cooler side. Perhaps a better solution would be to use something to wrap the left side of the handlebar with something to mimic the thermal insulation of the throttle tube on the right side, so that they would be balanced. You could always fix an old throttle tube to the left side so that it wouldn’t rotate and you’d be all set. Except that you would have to buy two sets of rubber grips because as you know on a standard set of motorcycle grips, the right grip inside diameter is bigger to accommodate the throttle tube (so the rubber is thinner, which also contributes to why the right side would feel hotter if the grip heaters were installed with no modifications to the left side to accommodate the difference). Then there is the issue of what folks use these things for. I was surprised when I read Paul Iceman Mondor’s experience using similar heaters to keep camera gear warm during an epic freezing winter trip across Canada. Read about his incredible journey here: http://www.advrider.com/forums/showthread.php?t=230898 In Paul’s own words: “At one point I am going down the road and I start to smell something! It is smelling sweet. Really freaking sweet! I am going “Oh Shit! I am losing coolant!” I stop on the side of the road and nothing? Frosty’s engine is dry! Must be something in the air! An hour later it is still smelling like this! I stop again and I smell the exhaust to see if I am burning coolant! Nope! What the hell!? I keep going an then I stop to take a picture. I open my tank bag and SMOKE is coming out! What the %$#&! I get my cameras out! $3000 of cameras and hardware and the towel that is sitting at the bottom of my tank bag is burning and smoking. I throw it in the snow and look at my stuff to make sure nothing is damaged. The Oxford Wrap around heated grips I am using to warm the bag so my video equipment works have heated so much that it set the bag on fire. My ear plugs case is melted to crap. My liner keeping the cameras from direct contact with the grips is melted and part of the wire for the digital camera battery pack has melted as well.” So clearly one has to be careful of where they choose to use this type of heater. If you want them to not be as hot as the sun, you could put the low heat setting resistor in series before (or after) the heater elements in the wiring circuit. If they are still too hot, add another resistor in series. You might be able to order another resistor from Kimpex, or just visit a Radio Shack, Circuit City, or whatever to get one. Something to keep in mind is that these resistors also get quite hot while soaking up some of the voltage drop, so be careful of where you mount them. What’s left to do? Well I am going to mount up a second throttle tube or something like it to my left handlebar to balance out the heat transfer on both sides when I install a new set of heaters on my bike. The ones I used in this test are toast. I just have to figure out an appropriate way to fix the throttle tube to the bar so it won’t turn and cut off the cable attaching portion. I am also going to use a solenoid to isolate the grip heater circuit from the battery when the bike is turned off. The triggered side of the solenoid will be wired to the ignition so that it only enables the power to get to the grip heater on/off toggle switch when the ignition is on. One last thin is that the circuit will also have a fuse. Since the grip heaters only draw 2.32 amps, so a 5 amp fuse should be fine. Please contribute any advice or experience with this style grip heater (on snowmobiles, ATVs, or motorcycles). Thanks. EDIT: OK, so I read at thumpertalk that there are grip heaters available that have different watt ratings for each side. Presumably, the right side would put out less heat. http://www.thumpertalk.com/forum/showthread.php?t=574261 Perhaps I should just get a set of these.