I live in Western Canada and have an unheated hangar. Out here, winter comes around every year. We operate a farm that that has something in excess of 75 batteries on the place in machines varying from garden equipment to Caterpillar tractors. Many of our farm machines sit unused (or used only very occasionally) through the winter months. We do not have any heated machinery storage except for my wife's car and my pickup truck. Some of our machinery sits outside all winter. (It's a DRY cold.)Obviously, equipping all these batteries with battery minders is as impractical as finding a place to store all these batteries in our heated shop. So this is what we do:
When putting machines into winter storage, be sure that battery electrolyte levels are full, that the battery is fully charged, that terminals are clean and that the ENTIRE BATTERY IS CLEAN AND DRY.
Disconnect at least one battery cable if there is ANY chance whatever of any parasitic current draw (clock, on-board computer, etc.). (Also reduces the fire hazard.) Since the airplane has a master disconnect switch, this is taken care of automatically.
We try to check our batteries every couple of months. (It's something that tends to be put off so I'm embarrassed to admit we sometimes only get around to doing it maybe once during the winter.) There is no such thing as a perfect insulator so any battery case will permit a tiny bit of current to migrate between the posts. If a battery's voltage is down we'll put a charger on it for a while.
Yes, sometimes we'll discover in the spring that the "Battery Fairy" has cast an evil spell on a battery during the winter but that battery was probably ready to fail anyway. The fact is, we don't buy any more batteries in April than we do in August, nor in January than we do in July.
I normally change out my airplane battery after four or five years and put the old one on something like a garden tractor or other machine that uses a small engine.
I don't care if my airplane battery is built by Gill or Concord. If one of them wasn't any good they would not have remained in business all these many years.
It is my carefully considered opinion that if a battery is taken care of properly a battery minder is unnecessary.
Don Ostergard
Drumheller AB
c-flhv@magtech.ca