12.9v on or off the charger? That's too low if on the charger. Even the smallest trickle chargers put out ~13.5v
It is possible to have a one of the six cells go bad, reducing the battery's appropriate full charge voltage to 10.6 instead of 12.7 the charger is dumb and keeps trying to put as much as 14.7 into the battery. This extra voltage overcharges the battery and boils off electrolyte. Under this condition the battery voltage may never get to 14.7 but it can easily get to 12.7. It will quickly decay and stabilize near 10.6-ish when the charger is removed. This may take a few hours to occur. If/When a load is applied the voltage will drop dramatically and stabilize near 10.6v. If this is the case then you need a new battery. Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD On Sun, Jul 15, 2018, 7:29 AM Danny Haughey via CnC-List < cnc-list@cnc-list.com> wrote: > Hi Rick, > Thank you for the insight. The start battery showed just 12.1 when I put > it on the charger. I just went out and battery now shows full at 12.9 > volts. > > It seems like the charge isn't getting to the batteries. This is one > system I haven't dug into yet. I guess that's going to change... > > I think I need to find a diagram somewhere > > > > Thanks, > Danny > > -------- Original message -------- > From: Rick Brass via CnC-List <cnc-list@cnc-list.com> > Date: 7/14/18 11:09 PM (GMT-05:00) > To: cnc-list@cnc-list.com > Cc: Rick Brass <rickbr...@earthlink.net> > Subject: Re: Stus-List Charging issues > > Generally, yes, if you are showing about 14 volts when the engine is > running, the alternator is probably OK. > > > > When you say the start battery is not charging, is it safe to assume that > the start battery will not start the engine? > > > > Under normal circumstances, and depending on the Amp-Hour capacity of the > start battery, it will probably never get below 95% to 99% state of charge. > (Unless, of course, you are using it to also power your house loads.) > > > > For example, the 36 HP Universal in my 38 draws 175 amps for about 30 > seconds in starting, or about 1.4 AH. That is about 1.3% discharge on the > 105AH deep cycle battery I use for starting. (And only for starting except > in an emergency) > > > > So the start battery is capable of reaching full charge in just a few > minutes of engine run time, and the full output from the alternator then > gets directed to the house bank if that is at a lower state of charge. If > both are fully charged, the current flow just creates heat. > > > > Check your start battery with a volt meter and both engine and battery > switch turned off. If you get 12.6 volts or more, everything is probably OK. > > > > If the start battery won’t start the motor, you probably need a new > battery. > > > > Rick Brass > > Washington, NC > > > > > > > > *From:* CnC-List [mailto:cnc-list-boun...@cnc-list.com] *On Behalf Of *Danny > Haughey via CnC-List > *Sent:* Saturday, July 14, 2018 7:31 PM > *To:* cnc-list@cnc-list.com > *Cc:* Danny Haughey <djhaug...@juno.com> > *Subject:* Stus-List Charging issues > > > > So my gauge shows 14amps while motoring but after a long motoring trip my > starting battery and house batteries are not charging. The house batteries > charge under shore power. > > > > I'm taking the starting battery home to throw on a charger to see if it > will take a charge. If oin l I'm seeing the 14 amps can I assume the > alternator is working? > > > > > > > > Thanks, > > Danny > _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > >
_______________________________________________ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray
