Vinny

A "remote temperature sensor" typically is either bolted to the Negative (ground) terminal of one battery... Or another option is to get a piece of styrofoam, carve out a hole for the sensor, and put it on the side of the battery (glue, jam in between two batteries, etc.).

Most solar charge controllers have an internal sensor that measures ambient controller temperature, and assume that this is "close enough" to the actual battery bank temperature (cold room, cold bank; hot room, hot battery bank).

Lead Acid batteries charging voltage is adjusted to the battery temperature. Hot batteries, reduce charging voltage, cold batteries, increase charging voltage.

For Lead acid batteries, typically the thermal offset is -0.005 volts per degree C per cell (with ~25C being room temperature/zero offset voltage).

Generally, charge controllers should be closer to the battery bank/bus. You do not want a lot of voltage drop from the controller to the battery bus. Accurate charging voltage for the controller... (for 12 volt battery bank, maximum voltage drop should be ~0.05 to 0.10 volts under full charging current).

-Bill