On Apr 18, 2009, at 9:07 AM, Skip Gundlach wrote: > 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)? > > 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?
Skip, Windsun, a solar equipment provider that seems to be very well regarded and quoted/linked in many places when I was doing my homework, has a pretty good FAQ on batteries here (no connection what so ever to the company): http://www.windsun.com/Batteries/Battery_FAQ.htm The relevant part: http://www.windsun.com/Batteries/Battery_FAQ.htm#Cycles%20vs%20Life Has graphs, etc. I can't find the link to Trojans own publication, but their numbers back up Windsun's and Norms and everyone else's going from memory: 50% DoD is the sweet spot for lifespan and usability. Also, I'll echo what Norm, Ben, and James have said about under/over charging, Victron's reference library, etc. 40% as Ben (I think?) said is the the maximum number of cycles point, but you're carrying more weight for less usable watts. Remember to factor in charge acceptance rate when dealing with charging inputs, etc. (seen/heard too many "just stick a bigger alternator on your engine" comments to 'cure' battery and charging problems). For flooded it's the C/8 rate, which is about 108 amps for your setup (C20 is 435Ah per, yes?) at bulk rate. Not really a huge concern in your case for renewables, but useful to figure out what RPM to run the engine if you have the temp/ output curve for your alternator at different RPM (or maximum usable RPM in order not to waste fuel). Hope that helps Regards, Dan _______________________________________________ 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
