One big issue here is that a lot depends on how much you use your batteries and how much you use your engine. If you motor a lot, you may have a chance of recharging the batteries (fully or close to it and even overcharging them (as Joe said)). But if you mostly sail and use the engine as auxiliary propulsion, you would hardly ever reach the full charge. This is one of the many reasons why many people install quite complex charging systems, especially, if they use any of the higher end batteries (e.g. the AGMs like to be fully charged after a discharge and require more complex charging curve).
Marek (in Ottawa) (still on hard, but there is a light at the end of that tunnel) From: Della Barba, Joe via CnC-List Sent: Tuesday, May 06, 2014 12:46 PM To: Rich Knowles ; [email protected] ; [email protected] Subject: Re: Stus-List Charging with engine, was mixed batteries An alternator with a fixed set point will try and reach that voltage but not go over. It may not be able to reach it if the batteries are low and/or demand is high, but it will not go over. I have an adjustable regulator with a set screw to turn the set point from about 12 to 15 volts. Various “3 stage” or ‘smart” regulators will vary the set point according to their built-in programs and user settings. Some have temperature sensors that will change the set point according to alternator temp, battery temp, or both. For an example, a regulator might supply 14.4 volts for bulk and absorption stages and 13.5 volts for the float stage. This is a pretty complicated subject for an email list, but long-story-short is you can destroy very expensive batteries very quickly by not paying attention to what your alternator is trying to do. Ages ago I got an expensive Rolls 4D battery and the 13.8 volt setting on my stock 35 amp alternator was not even *close* to being able to adequately charge this battery and it sulfated to death in about a year or two L Conversely gel batteries are quickly ruined by a regulator set over about 14.0/14.1 volts. Joe Della Barba Coquina C&C 35 MK I From: CnC-List [mailto:[email protected]] On Behalf Of Rich Knowles via CnC-List Sent: Tuesday, May 06, 2014 12:26 PM To: [email protected]; [email protected] Subject: Re: Stus-List Charging with engine, was mixed batteries An alternator, if no external smart regulator is present, will put out whatever the internal regulator is set at. It could be anything from 13.4 V to around 14. For a shore charger it is best to have a smart charger that will reduce the voltage to around 13.2 to avoid boiling off the electrolyte during prolonged charging. Rich On May 6, 2014, at 12:54, via CnC-List <[email protected]> wrote: At the risk of beating a dead horse (battery), I have one more question for the list. When the average sailboat engine is running, what is the likely charging voltage to the battery or batteries? Unless one has an alternator output controller which matches the recommended voltages for the batteries being charged, it seems that they would be charged with whatever voltage the alternator supplies. If this is the case, and if one rarely charges the battery(s) at the dock, it seems a little pointless to fret over what the voltage profile the battery charger provides, since the batteries are likely charged mostly when the engine is running without such a controller. Charlie Nelson Water Phantom [email protected] _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com [email protected] -------------------------------------------------------------------------------- _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com [email protected]
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