[Mtntrek]

Similar to the Magnum inverter / charger whose remote temperature probe is to be secured in the battery compartment on or near the battery bank. Since batteries (especially AGMs) can be damaged by overcharging in high ambient conditions, better charge controllers throttle their output. Generally temps much over 77 deg.F charge controllers should scale back from their 100% bulk, absorb. programmed output(s).
Often these probes have an isolated ring that can be secured to an unused aux. lug on a neg. terminal.