48 to 12v with Heating Pads connection

[GyroGypsy]

All, See attached proposed diagram for connecting Heating pad for my Lithium phosphate batteries

I bought at 48v to 12v step down converter, it comes with a 20 amp fuse connected to the 48v hot side.
We already have 2x 48v batteries but our problem is that they get very cold during the winter months and we need to keep them heated.
We bought TWO Facon 13.5V 65watt heating pads we would like to attach to our batteries. (Attach in Parallel)

Any thoughts on this? not sure if i've missed anything with this set up. the heating pads should shut off at 68F and turn on at 45F.

Is there a wiring diagram or any other videos i could look at to get a guide? i just don't have the confidence for this at this time.
Again, a bit of a novice here. would love some help/feedback

48-12v link
facon water heating pad

I tried the Facon 7x25" tank heating pads, attached to .020 aluminum sheets, sandwiched between two Tesla S modules. The internal Facon thermostats would short cycle, only heating for about a minute, then be shut down for the next 20 minutes or so, while the insulated battery compartment temperature continued to fall. One of the Facon pads ran less than 2 amps, or less than 50% of the specified power. Still looking for similar sized silicon pads that i will externally control.