Battery operated signals

I have seen a few batterie powered signals at leased two of them were hooked up to a solar pannel. I would guess that maybe someone looks over the batteries once a month?? and maybe more ofton in the winter??

Interesting question. There are still a number of derelict battery pits along the former CNJ mainline, now NJT Raritan Valley Line. At one time the Jersey Central employed some 40,000 (!) from what I've read so there certainly was the possibility of manpower intensive changeouts, in the days before solar chargers. Before solid state electronics, even where utility power was available, chargers would be somewhat problematic, I suppose. Maybe drycells were used.

The batteries located at the distant end of the track circuits are large primary cells that are typically good for 6 months or more. These batteries only operate the track relay and do not light the signals, gates etc which have their own power source.

A typical primary battery is carbon-zinc with a caustic electrolyte and has a capacity of 1100-1300 amp-hours. There would usually be 2 or 3 batteries in parallel for a total capacity of up to 3900 amp-hours. At an average drain of 0.5 amps, this would theoretically provide ample reserve capacity for 6 months or more. Cold weather and track conditions would affect the life but 6 months would be typical. The batteries would be inspected monthly and replaced when the voltage began to deteriorate.

Most DC crossing circuits now use a diode at the distant end with ac voltage applied to the rails from the crossing equipment. This eliminates the need for a battery or power source at the distant end of the circuits.
Many crossing circuits now use "motion detector" or "predictor" electronic technology instead of the simple DC track circuit.