Reward for lost Kraken!
Join Date: Apr 2006
Thanked 132 Times in 129 Posts
Rep Power: 11
Re: Lifeline Batteries
I find it sadly unamusing that even the battery makers keep contradicting their own information about how each type is best treated or used. Even in Lifeline's little blurb about battery life, I'm guessing they made an "oops" because their #1 scenario for best battery life does not mention equalizing at all--and they're one of the few AGM makes who say to equalize their AGMs. While most everyone else says that is unnecessary or will kill them.
"BTW this is the hidden cost of the wet cells..acceptance rate and" Chef, I would note that the acceptance rate for wet cells is normally given as C/5 (one fifth of the charge capacity) while it is given as C/4 for AGMs. That means wet cells can be charged at 20% of their rated capacity while AGMs can be charged at 25%. A real difference--but not a huge one. And while many folks have reported charing AGMs way faster for years with good results, again, that's just what the folks who make them have to say about it.
After messing about with alternator data sheets, pulleys, etc. I have come to expect any "stock, built to a price" boat to simply be set up WRONG for the best charging. It starts with alternators, which simply cost more when they are sized to produce full power at low speeds (idle, cruising) while not overheating at high speeds.
I find wet lead to be a tar baby, I just know every time I get near them, something will be ruined by acid. Pants, shirt, parka, carpet...something. But that's just my luck. I try to keep sone disposable clothing and lots of cardboard and plastic around when I'm near them.
And AGM is simply pricey, no matter how you look at it. Maybe a 30% premium for AGM flat plates, 50% for spiral cells (Optima) which also have less capacity because they are a box full of tubes, so the box isn't full of lead. Case-for-case size, spirals will have about 10% less capacity.
But AGM does have one compelling case, and that's low self-discharge. If the batteries are going to sit without being trickle-charged, i.e. over the winter while the boat is on the hard with power not always available, that's where AGMs win. They can SIT for six months and pretty much come back to 100% afterwards, while a wet lead battery starts to take permanent sulphite damage at 30 days. If you're living on board or boating every week all year round, or have reliable power (dockside or solar) that's not an issue.
I applaude the folks like bt and Maine who have tried to set up battery banks on the bench and get some objective long-term testing done. And I'm astounded that Maine could leave wet calls all winter and get no capaity loss, cold or no cold. I only wish the industry would try as hard to lose the smoke and mirrors.
Last edited by hellosailor; 06-02-2012 at 11:18 AM.