The conventional wisdom says to never discharge your batteries more than 50% of their rated capacity and recharge them promptly. The less you discharge them, the longer they last. The 50% level is the working compromise between using them and saving them.
Asking for "unreasonable" performance from your batteries is defined entirely by you. If you never discharge your battery, keeping it on float, it will last the longest (although there is some evidence that exercising the battery periodically is necessary for good performance, in submarines at least). Any use shortens its life. Other than the 50% rule to keep from stressing the plates "too much", and prompt recharging to reduce sulphating the cells "too much", you just have to keep in mind that discharging the batteries shortens their life, and not discharging the batteries makes them useless. Only you can decide what is tolerable in between those two extremes. According to Home Power (available at Barnes & Nobel), chronic undercharging of batteries is the number one reason for premature failure, and chronic overcharging is the number two reason. The majority of real-world experience in living from batteries comes from the folks who subscribe to and are written about in Home Power magazine. All their back issues are available on DVD. I have two pair of Trojan L-16 batteries. I find I use about 100 A/H per day when off the boat, mostly for the freezer and the reefer, and between 200 and 300 A/H when on the boat mostly from TV and computers with some from galley, lighting, and tools. This is some serious use. They last about four years until cells start to short. Our laptops have 2 Mpixel screens requiring heavy duty "car cords", and our TV is a 32" Sony LCD with satellite active antenna has its power cost too. When I look at our A/H meter and see more than 250 A/H on it I start to think about running the genset to recharge (and make RO water). You do need a way to "force" a full charge. We have a 8KW diesel genset in the engine room, but others have a Honda 2KW genset lashed on deck. Both work. I now have 840 watts of PV and am seriously thinking of adding more. I would like to completely eliminate using the genset. I also have two KISS wind gennys that I use occasionally too, but the PV panels are primary. If I have lots of wind and sun I can keep up, but I don't always have them both (or either). Norm S/V Bandersnatch Lying Julington Creek 30 07.695N 081 38.484W > 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? > > We have a variety of charging sources and differing loads which makes > for days when we may see close to 50%, and days when it never leaves > "full" - and since we can't "force" "full" reasonably, we want to make > sure we're not unreasonably asking for our batteries performance. > > Knowledgeable assistance appreciated, and your practice, whether > empirical or just "is" would also be appreciated. > > Thanks. > > L8R > _______________________________________________ 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
