Which begs the question, isn't a heating pad just a wire run up and down the insides of a rubber pad? We have provided a link to a helpful PDF which outlines the wiring aspect in the blog, at the end of step 4.

Heating | DC GUY, Power To The People - For Less DIY Battery Heating | DC GUY, Power To The People - For Less

We also consider how the heater mat must be fixed to a surface and the type of control system or safety features required. The battery does not produce a lot of heat internally, and the heat pad does not preclude heat transfer, as much of the heat is transferred through the sides that are not covered. The wire was then just wrapped round hooks at the end of the frame is a zigzag pattern to use up the calculated length. I have the smaller one in my underbody pack, and its been good down to 20F so far (1/2" XPS insulation, and 5 exterior sides).Once the temperature of the ambient temperature sensor reaches 45°F, the switch is disabled, stopping current from flowing through the pad. Easy to install with Self-adhesive design and 3mm thickness foam insulation prevents heat from disappearing rapidly.

RS PRO Silicone Heater Mat, 2 W, 12 V dc | RS

I have read the instructions, as well, and there are several incorrect statements, and the photos do not show how you are wiring the pad. After the thermal wraps are in place, wire each heating pad to the main fuse panel or directly to the lithium battery using the included 10 amp fuse (we installed ours directly to the batteries using positive and negative bus bars). Placing a heating pad below the battery will eliminate the only face of six that is causing the low temperature problems.

If you’d like to measure the draw from the heat pad in itself, then yes, you want to wire the heat pad up to the load side of the shunt. I started by deciding the approximate power rating I estimated would be required to warm the area I wanted.

Heat Pad with Battle Born Batteries How to Use a Heat Pad with Battle Born Batteries

Negative push-in connector: two black (negative) wires from the heat pad and one white (negative) wire from the temperature sensor.

I would personally put the batteries in a insulated container, then add a thin sheet of conductive material like sheet aluminum over the pad so that the heat it produces can warm up your entire battery bank. I would think that 36-38° on and 40-45° off would suit our needs, you don't need to do anything other than keep it above 32°. We all know that lfp batteries shouldn't be charged below 32°f and with my batteries the EMS will shut charging down if any of the 20 prismatic cells do drop below 32°f, after 44 months we were in extreme cold and couldn't move from it like we normally would do. Heating for much time using a battery is not going to work because the watt-hours in the battery will only power the heating pad for a fairly short time. Some ballpark math indicates that if you insulate that pack with 1/2-3/4" XPS all around, then a 60W heating pad should be good below zero.