Because you can't SEE the damage and the odds are you don't have access to the equipment to do any real meaningful SOC testing.
I do have the test equipment, about $5000.00 worth, I am also one of the only marine electrical systems techs offering physical capacity testing. I am one of the few who has ponied up for the equipment to do that.
I also work directly with battery manufacturers and am currently in the middle of some long term PSOC testing for one of them right now. This is a new AGM variant that looks very, very promising. I compile data, run testing and send the data off to the manufacturer.. This testing has been geared specifically at marine use and how to best develop a battery that can survive this type of abuse. This company understands not everyone will move to LiFePO4 or other chemistries so is working hard to build a sulfation resistant lead acid battery. This gives me excellent access to some of the best engineers in the business, and still, I leave my LA batteries on board all winter......
Yep, I leave my batteries on-board 100% disconnected but charged/equalized before disconnecting. I can do physical capacity tests to see exactly the impact it has. I have done this multiple times. (capacitance, pulsed load and carbon pile testing is a joke compared to a physical 20 hour capacity test) It has not lead to shorter life and in fact the batteries I service last a good long serviceable life nowhere close to 3 years..
Heck even my AGM reserve battery, that winters on-board, is not on a charge all winter and my boat is 4' from my house. I use one of the smartest chargers made yet I still won't leave it unattended because there is simply no need to do that in the winter... I simply won't do that to my battery when there is less than zero need to.....
And yet, they ALL will say what I just said. Thirty days, and you've probably damaged the batteries. 90 days, and you've definitely damaged the batteries.
And because you don't have the equipment you believe them, then connect to a charger and leave it there thinking it will do good
. Remember these are the folks trying to sell you lead
who are telling you to leave a battery on constant charge....
Most of these chargers are certified pieces of $hit and are far from anything even resembling smart. They do nothing to prevent stratification during winter storage and all they do is hold the voltage slightly above resting with mA level current that serves no real purpose in cold weather because there is little to no self discharge going on..
My now 8 year old Wal*Mart batteries have outlasted many sets of Trojan's left on charge but yet they were left on-board every winter not on charge.
Can't be? Cold weather slows all the chemical process dramatically including sulfation and self discharge. This is chemistry 101..
You think doing nothing works well enough? OK, do nothing. They'll be happy to sell you new batteries every three years instead of every six or eight years.
I had a set of 12 year old GEL's on my bench two weeks ago for capacity testing. They have been on-board for 12 years and not charged in the off season... I have many customers well beyond 8 years with typical wet cells all stored on-board & disconnected. As long as the batteries are put away properly
the only real effect you have is stratification but a constant float charger will not prevent that either. Oh the marketers will have you believe their charger is as smart as Einstein they do still do not prevent stratification.It is is pure hog wash that a constant float voltage prevents stratification. You need to roll
the electrolyte to do that and this requires voltages above gassing... So now you have stratification WITH additional charge current. Think about it, I do, and this is one of many reasons I will not leave a battery in cold storage on constant float.....
I would personally rather see an owner hit them with 14.6V - 15.5V once or twice per winter, a good gassing voltage, than risk burning their boat down with a crappy "smart" charger. Most yards disallow any sort of charging during the winter for just this reason..
Not my opinion. Objective fact, repeated and confirmed by every business that's in the business of making batteries.
are simply opinion
when it comes to winter storage.