I saw the note on the drain on the 12V battery for the heated seats. Does anyone know if the cabin resistance heating is 12V as well? If so, do you think it would help much to add a deep cycle battery (or two) in the trunk connected to a reasonably sized AC inverter connected to a battery charger and then plugging this into one of the 12V ports (cigarette lighter) to "charge" the 12V battery when running the heat and the heated seats? This might get back some of the range lost in the winter. Still would have to recharge the batteries added every time you used them... Again, just an off the wall thought.
There is no such thing as a free lunch! If you're using the car's energy to recharge a battery to run things in the car, you are actually in a lose-lose game because of the losses from all the inverting/converting and electrical to chemical to electrical energy conversions. To say nothing of the losses/dangers with carrying all that weight around. Finally, the DC ports in the car are of very limited capacity. They would take forever to charge a deep cycle battery, let alone 2.
I agree that this is a little off the wall. I wasn't planning on charging the deep cycles from the car. Think of it as augmenting the high voltage battery capacity of the car. Adding a couple of cells to help pull the 12V DC load in the car so the high voltage battery is not drained doing the job. You would discharge the deep cycle batteries and then recharge them at night at 120V. Even so, you are right that you wouldn't want to push more than 10A back in this way (circuit is probably fused at 10 or 15A) and that is only 0.12kWh per hour saving from the battery drain. Not worth the trouble for the 100 lbs extra you would be carrying... So you are right, nothing is for free...
