Well, the heater... ( I can't prove what the heater puts out )... the 24v DC transformer puts out 75 watts.

75 watts is more than most electric blankets for your bed... but your bedroom has a pretty decent ambient to begin with.... OTOH, the battery is in a tight confined space with no air circulation... so 75w could be a lot.

I guess weak is a matter of opinion, but 75w is 75w.

In a 40 degree garage ( so no wind or anything ) my Tav would be 60's to near 70 degrees with 3 to 3.5 hours of plug time.

In a 20 degree garage, my Tav is normally in the 50's each A.M.

The very first time I used it, (40 degree garage) I got a Tav over 85'F and the car kicked on the A/C when I turned the key. Not a desired event, but that has never happened since. I have to wonder if this part is electronically contolled, or thermostatically controlled... and maybe the car had to "learn" the first time?

You know it would help if these darn things came with directions!
-John

P.S. Mark - it may be counter productive to leave it on all night.... if there is a thermostat that says "kick on at 40 degrees, kick off at 65". I know in industrial areas with heat trace on pipes, that how some work. Perhaps in the middle of the night, yours exceeded the upper limit ( I don't know what that is ) and kicked off. Then, it chilled a while, but never came back on before you turned the key. I'm 99% there is a thermostat control. The amp draw on mine varries, but I have not kept good records for this.

 

John, I'm also 99% sure there is a thermostat involved with the battery heating cycle, and located inside the battery compartment. Otherwise, if the heater were plugged in continuously, the constant 75-watt heater, applied to the sealed battery with carpet over it would eventually 'fry' something. The thermostat might be something simple like a bi-metal contact that opens/closes the heater input circuit as the temp raises and falls. If this is the case, then after the requisite amount of time to warm the battery, additonal plug-in time would be waste energy.

I still have an unresolved issue with my 08 FEH battery warmer circuit, where I have the plug at the battery, but can't locate the other end in the engine compartment. I've come to the conclusion it doesn't terminate in a plug like the 05-07 models. Then I checked continuity of the two input wires on the receptacle at the battery, and showed an open circuit. But come to think of it, the battery was already WARM when I checked it that evening. So if the thermostat in the battery is a bi-metal make/brake for the input circuit, AND the battery was already warm, then the circuit would appear open. I obviously still have more checking to do when the battery is COLD, -> check input resistance, and then apply 24VDC while monitoring current draw to see if the heater really is hooked up on the 08 FEH AWD. Now to find the time to do this early in the morning between work and wife demands for the car

 

This thread is already pretty old, but I don't see any better one to post this to.....so, here goes...

I have a 2008 FEH that I purchased new in late 2007. It's been a great vehicle, but every time I visit the dealer, & see the Salesman I bought it from....AND, it's colder than HE-double-hockey-sticks outside.......I ask him WHY HE NEVER OFFERED THE #*€% COLD-WEATHER OPTION .???? I don't have the block heater, & MORE IMPORTANTLY, DON'T HAVE THE BATTERY HEATER PARTS TO THE WIRING HARNESS ,!!!! I asked about getting it installed afterwards, & was told 'NO !!!!' I even purchased the transformer & front harness from another dealer.....but, when I was told that hooking it up could invalidate the battery warranty, I gave up for a while. THEN, I found this and put one of the Stair Tread heating mats on top of the battery, attached to the control unit from the same company....AND IT WORKS ,!!!! This winter, as we've had multiple -20 degree mornings....the battery has not gone down overnight AT ALL !!!! I put a thermostat in line that only allows it to come on if the ambient temp is below +20 degrees F. Wonderful. Cost me about $145, but worth every penny. It keeps the area somewhere around 50 degrees overnight. Not overly hot, just enough to help !!

Here's the website :

http://www.heattrak.com/Products/Res...-Products.htm#

Hope this helps someone else avoid the problems with the Traction Battery constantly discharging in frigid weather to keep itself warm !!