I thought that was the whole thing with tenders in that you didn't have to disconnect the batteries to prevent slow discharge from stray current. I would surely think that if you charged a battery fully, disconnected it till ready for use, it should last a long long time without any battery tender attached. I put the Walmart supplied Schumacher battery tenders on everything that has a battery so I don't have to unhook and rehook the terminals and it seems to work. I still have the original battery in my 2007 Silverado Z71 Classic which was made in 2006 so it is 6 years and counting. It has been discharged fully a couple times, once from leaving my trailer (electric brakes) hooked up for a week and parked outside and another time before I put on the tender, I left my GPS and radar detector on for 8 weeks when I was out of country and came back to a completely dead battery. Jumper started it both times and let the alternator charge it back up and it still starts well even in cold weather. I have never had a battery last more than 4.5 years before as the heat in the south kills them pretty quickly.
People up here whine about the cold, but I guess people everywhere whine about the weather..... yes, heat seems to be pretty tough on batteries. I've traveled in the SW, but never lived there (it is one part of the USA I would like to, though) - I suspect that many batteries just run out of water, never being topped up.
As we are discussing, the first thing to recognize is the problem of tons-of-onboard-electronics-in-idle-mode slowly draining a battery, in modern vehicles. And, that's just the OE stuff, not counting the nice to have add-on toys that drained yours.
A battery tender used on a modern vehicle will offset this constant drain, as you practice. (Providing.... the tender keeps working, the "BetterHalf"/kids don't unplug it on you, the GFI doesn't trip....).
Jerry's approach of disconnecting a battery (as posted, I like the simple low cost disconnect switches myself) will work too, in the short/medium term. All batteries will self-discharge (some types slower than others) eventually, even with no load at all connected - Jerry deals with that issue by charging with a bigger charger before the
long term storage time frame hits.
I also like that a disconnected battery is a deterrent (OK, realistically just a minor one) to vehicle theft.
As some people have posted here, if you use low cost tenders on equipment parked outdoors, some will fail due to moisture damage. If you are not checking regularly, you can then end up with an equipment battery sitting there with an extra load on it from a baffed out battery minder. That was before this new class of IP65 sealed minder/tenders came along..... one of the reasons I plunked down some of my limited cash for one recently is that I am truly impressed with that aspect of these new ones, it is useful to me.
My comment was mainly to agree that Jerry had a viable approach to dealing with this modern vehicle problem, not to say that tender/minders do not work.
Your vehicles, equipment, indoor storage space, local climate and availability of 120VAC will be factors in deciding which approach makes more sense.
Rgds, D.
Some vehicles today 'learn' and store driving habits I have read.
