On Fri, Apr 17, 2009 at 09:07:21PM -0400, Skip Gundlach wrote: > > We have new, L16H batteries in our 880AH house bank, flooded cell. In > a perfect world to make them last longest, I know that they'd never be > allowed to drop below 100% capacity - but then, what's the point of > having a battery?
They make pretty boat decorations? :) > So, the question (well, maybe two) is: > > What is the recommended, real-world cycle? That is, how low do you > take your flooded batteries on a regular basis? Related, is there a > readily available source for information on the numbers of cycles to a > given percentage of discharge in a battery life span? I.e., 500 > cycles to 50% and back to 100% but only 100 cycles to 20% and up to > 75%, or the like (recognizing that these numbers have no relation to > any battery made)? I don't know of any resource of that kind, unfortunately, but my approach - which at least allows some kind of handle on the process - is to consider over-discharging (which I define as anything below 60% on heavy-duty batteries) as progressive degrees of damage; the further down you go, the more damage there is. If I had to put numbers on it, I'd say that completely cycling a heavy duty battery (100% to 0%) a hundred times or fewer will kill it dead. With "perfect" usage - and by that I mean never letting the total drop below 60% or so, recharging at as high a rate as practicable (up to 20% of AH capacity), and equalizing the batteries on a regular schedule - you could get several thousand cycles out of it. That's really what you're working for: trying to maximize that number. Anytime you abuse the batteries, you're shifting it down. > Second, what do those of you with flooded cells, not connected to the > shore power all the time (that is, full-time cruisers or rarely > connected to the utility-based power cord) have as a practice? What > charge regime, and how, do you observe? Never below X%, seldom above > Y%/Always more than Y% of capacity? Yeah, sorta, more or less. In general, except sometimes. :) The regime that I described above is what I try for; however, the realities of living aboard, the necessity of occasional heavy power use, sometimes being away from the boat for weeks at a time, etc. all militate against that "perfect" usage. As a result, I expect (based on all my previous experience) 4 to 5 years out of a set of batteries based on my usage patterns. I do want to point out that part of my success with keeping my batteries alive as long as I do is thanks to the skipper of "Bandersnatch": a number of years ago, I listened to Norm's advice about equalizing batteries much more often than recommended by even the most conservative battery manufacturers, and testing the individual cells with a hydrometer to get a feel for what's actually going on inside. It's made a really big difference. > Knowledgeable assistance appreciated, and your practice, whether > empirical or just "is" would also be appreciated. Everything I know about this, I've learned from my years on the water. Oddly enough, my understanding of matters electrical and electronic has mattered very little - this is a science all its own, combining chemistry, physics, common sense, brute force, and experience in arbitrary amounts. I hope you find it helpful. -- * Ben Okopnik * Editor-in-Chief, Linux Gazette * http://LinuxGazette.NET * _______________________________________________ Liveaboard mailing list [email protected] To adjust your membership settings over the web http://www.liveaboardnow.org/mailman/listinfo/liveaboard To subscribe send an email to [email protected] To unsubscribe send an email to [email protected] The archives are at http://www.liveaboardnow.org/pipermail/liveaboard/ To search the archives http://www.mail-archive.com/[email protected] The Mailman Users Guide can be found here http://www.gnu.org/software/mailman/mailman-member/index.html
