Hmmmm . . . I see. The issue is that we use the boat a lot and routinely spend two nights on the hook. The extra 40 amp hours would go a long way.
I just ordered a Victron Battery Meter; maybe I'll leave the batteries as is and get this installed. Then I can see my actual power consumption and make a call after that. Perhaps a new regulator would limit the amp draw and protect the alternator? --- In [email protected], "Phil Agur" <pja...@...> wrote: > > Mike, > > > > Except the moral of my story was your alternator's rating is based on the > charge rate dropping fairly quickly to 50% of it rating or under 28 amps for > any extended charging. Two 79 Ah batteries 50% down would most certainly > push you alternator's case temperature to its limits. If that melts the > brush holders then you're done after that. IMHO you definitely need to > maintain the factory A-B switch approach so you can direct the alternator to > a single battery at a time until they are mostly recovered, especially if > you ever need to use the jumper pack. > > > > It might be possible to parallel them up using a truck style battery > isolator in parallel with the A-B switch. The reason I say that is the > Isolator is a pair of large rectifiers in a heat sink. Each one creates a > .6V drop between the battery and the alternator output which slows the > initial charge rate. It would then also function as a diode blow out > preventer since the isolator would keep the alternator loaded even if a crew > member turned the A-B switch through Off while the engine was running at > speed. It still does feel as safe as the factory solution. > > > > Phil Agur > <http://www.catalina27.org/public_pages/profile270.htm> s/v Wing Tip > C270 LE #184 MMSI 366901790 > > > > > > From: [email protected] [mailto:[email protected]] On Behalf Of > mkeller23173 > Sent: Thursday, July 01, 2010 11:10 AM > To: [email protected] > Subject: [IC27A] Re: AGM Batteries > > > > > > Gotcha, we're on the same page, I misread. > > I think I've decided to wire the new batteries in parallel to increase the > amp hours. I have one of those car jumper packs I will bring as a backup > starting battery until I can install a real starting battery in the fall > (probably one of those small PWC ones will work). > > Regarding the alternator, my off the cuff calculations are as follows. Two > 79AH group 24 batteries = 158 amp hours total. Since we'd never drop below > 50% of those amp hours, the max that would be needed to put back into the > batteries is 79. We have a 55amp alternator on our Yanmar. Since AGMs can > draw as much as 75% of the needed amp hours, that really only leaves us with > a 4 amp larger draw than the alternator is capable of providing (59 vs 55). > I figure 50% would even be excessive so I think we're safe. > > Time will tell if I'm right. > > Thank you everyone for the help and comments, much appreciated! > > Mike >
