Thanks for the excellent questions for more details Paul!
i want to be able to heat the batteries between 50-70 degrees F.
i have 4 battery boxes, each has 3/4" PS insulation on the top, bottom and sides.
The front (engine compartment) box and rear box (behind rear axle) are square, have 6 batteries in a 3x2 arrangement.
The two side boxes (on either side of the drive shaft) have 4 batteries in a 4x1 arrangement.
In keep the input heat approx. equal for each battery, i use a 80w blanket for the 6 battery boxes (13.3w/battery) and a 50w blanket for the 4 battery boxes (12.5w/battery).
The warmers run off of 110V AC before and while i'm charging.
The scientist in me wants to be able to monitor the temperature of each box on a digital display, as well as control their temperatures.
i'm willing to spend a couple hundred as long as i have a solid reliable solution. i'm an electronics hobbist wanna be... i imagine building a PIC computer controlled device that has 4 inputs for the thermocouples in each box and 4 outputs that can switch the heaters on and off. Thanks!
Between what temperatures do you like to keep your battery boxes? How many battery boxes do you have? What is the watt ratting of each heater, or voltage and current rating. I assume that these heaters run off of 110 AC. Do you need to monitor the temperature or need any kind of gauges? How much are you willing to spend?
There are many solutions to temperature control, everything from using a thermostat for a house to using industrial PID controllers. One rather inexpensive solution does not use electronics at all. Many refrigerators use a simple sealed chamber that drives a pressure switch. As the temperature warms up the pressure increases and the pressure switch turns on the compressor. In your case you would want to invert the operation.
Paul
