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Catalina/Capri 25/250 Sailor's Forums

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On board charger

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Navy1
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USA
126 Posts

Initially Posted - 02/05/2009 : 17:23:53

I have a ProMariner Prosport 12 permanently installed to both my boat batteries, along with a Perko 4 position switch. My boat is stored inside in my own building. My question is wether it is better to leave the system plugged in constantly for keeping the batteries constantly topped off, or should I just hook up the shore power once every month or so to keep the batteries topped off. I use one lead acid battery in the system for starting only, and one AGM for the house battery. Thanks - Roger

Roger Richter

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jbkayaker
Captain

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USA
299 Posts

Response Posted - 02/05/2009 : 17:46:36

Frankly I don't know the capabilities of the chargers you are referencing. What I used to do was plug my charger into the boathouse lights. So the charger was ON whenever the boathouse lights were ON which was typically less than one hour a week. That reduces the possibility of a fire when nobody is there and it worked fine for me.

Edited by - jbkayaker on 02/05/2009 17:52:19

At Ease
Admiral

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672 Posts

Response Posted - 02/05/2009 : 18:59:50

As noted above, we don't know the capability (or limitations) of your charger. I have a good three stage charger on my boat, and a cheaper charger with a smart controller to keep it from frying the batteries, in my RV...so both stay plugged in all the time.

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OLarryR
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3440 Posts

Response Posted - 02/05/2009 : 21:54:08

Batteries discharge a little less than .5A/Day per battery in warm/summer weather and about .25A/Day per battery in cold weather. So, leaving the charger off for a month or so is no big deal. For example, my riding mower battery, I never charge it during the winter months (~Jan-Mar) and then charge it for the start of the new season and that battery always seems fine.

I'm not familiar with your charger but chances are the "12" stands for charging rate of 12A/Hr or if it has dual leads to the batteries, then 6A/hr per battery. Now that does not mean that when the batteries get to say 85-90% fully charged, it is only going to take another hour to get to a fully charged state. The way the chargers generally work is that as the battery gets closer to the fully charged state, the charging rate slows down. So, after a month or so, I would leave the charger on for a few days or more. Then turn it off for a month or so. You could take a voltmeter and while it only measures resting voltage, you could after having the charger hooked up for a few days, then wait a day with the charger off and measure the voltage. If it measures less than say 12.8 Volts, then I would leave the charger on longer. If it maintains voltage above that, then you could see if leaving the charger on for one day less each month, still maintains the voltage 12.8 or above.

My batteries are charged with a solar panel and solar controller. After the solar panel shuts down, the voltage is usually around 13.2 Volts. If it remains overcast for a day or two, then I get a better sense of the resting voltage and that is usually around 12.9 Volts. My batteries are not new. I have had the boat now since Oct 2005 and the PO had the batteries for at least a year or more before I bought the boat.

Edited by - OLarryR on 02/05/2009 21:59:23

piseas
Former Treasurer

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2017 Posts

Response Posted - 02/05/2009 : 22:51:49

Roger, I have shore power and 2 batteries. I sail most weekends and motor for about 1 hour that charge the batteries. I use my shore power once or twice a month overnite. That seems to do the trick for me.
Steve A

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Nautiduck
Master Marine Consultant

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3704 Posts

Response Posted - 02/06/2009 : 12:46:39

Over the winter I remove our two AGM batteries and put them on an inexpensive charger about once a month. Personally, I would unplug the shore power and just charge up every four weeks or so.

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Navy1
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USA
126 Posts

Response Posted - 02/08/2009 : 13:52:10

Thanks for the info guys. I will do as most of you say and just plug it in once a month or so. I will also check the voltage after a month, as you say, which is a good idea. Sometimes it funny why you don't think of some of the answers yourself. Has age got anything to do with that?

The Promariner ProSport 12 I refer to is a 12/24 volt, 12 amp for two battery banks, and is shown in Overtons & West Marine. It is a permanent installation unit that cost $139.99 in Overtons. Thanks - Roger

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Stu Jackson C34
Admiral

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844 Posts

Response Posted - 02/09/2009 : 16:01:40

You need to find out if your charger is a true three stage charger. If not, your charger could be killing your batteries. Read the West Marine Advisor on charging batteries, and also download and read the Ample Power Primer at www.amplepower.com.

Since you don't say how much you take OUT of your batteries when you use the boat, there's no way anyone can tell you how much you need to plug in to charge them fully. You need to do an energy budget, also discussed in the West Marine Advisors. (Whoops, I just looked and they've removed that great link. The idiots!)

The best thing you can do is charge them fully and leave them unplugged. Continuous float charging harms batteries.

Edited by - Stu Jackson C34 on 02/11/2009 11:42:19

essen48183
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USA
143 Posts

Response Posted - 02/10/2009 : 18:26:34

I have the same one. It charges two banks independently using the full 12 amps on one if needed up to 14.6 V in charging mode then conditions them by holding to 14.6 for a short time for conditioning mode, then switches to 13.something maintenence mode. I keep mine plugged in when not sailing, that's why I bought that charger. Keep that one plugged in. Doesn't matter what king of battery... those values change based on the little plastic colored thingys for AGM lead acid, etc.

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essen48183
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143 Posts

Response Posted - 02/10/2009 : 18:37:45

I should add my opinion on the 4 position switch. I think on sailboats with outboards with alternators and backup-pull starting... the utility of an "engine" and "house" battery is lost. On a powerboat or inboard diesel, this is necessary so you can get home. You deal with the complexity and nuisance of the switch for starting and charging to keep from being stranded. However, while you are using power you are using from one bank and are more likely to drop below 50% shortening your battery life. The weight of two batteries is better left to 2 deep cycle house batteries unswitched and placed as ballast where they are needed most... in a c250 in the bow instead of sandbags. If you remove 50 pounds from the aft and move them to the bow is is the same as adding 100 pounds of sand up front.

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Stu Jackson C34
Admiral

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844 Posts

Response Posted - 02/11/2009 : 11:29:05

Essen, very good point. On many of Catalina's larger boats there is a port list. So one day some guy smugly wrote in how he'd added 200 pounds of lead to offset the list. I wrote back: "Why didn't you just add more batteries?!?"

I also agree that for a C25 a battery switch for two separate batteries is not the way to go. The largest single house bank you can have is the best, and is appropriate for engine starting too, since it only consumes a very small amount of AHs, like maybe one! It also increases the life of the batteries because a smaller % of discharge with the same load on a larger bank increases the battery life.

Edited by - Stu Jackson C34 on 02/11/2009 11:45:07

britinusa
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5404 Posts

Response Posted - 02/11/2009 : 17:46:19

2pc.

We have a off|one|both|two battery switch. If one battery does take a nose dive in volts, we can switch to the other, but if no switch, then we would have two flat batteries.

Paul

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essen48183
Navigator

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USA
143 Posts

Response Posted - 02/11/2009 : 20:05:29

Correct, however, what we are saying is that the switch is unneccessary. It is worse for your batteries to drain one bank to a lower percentage and then switch over. It is better for the amount of amp hours to take it from both at the same time. For example if you had a 800 amp hours requirement based on your needs between charges, and you had two 1000 amp-hour batteries. Your batteries would last longer if you took 400 from each rather than 500 from one and 300 from the other. Sometimes if you weren;t right on top of things you might accidentaly take 600 and 200... really shortening the batteries life span. The best way to be sure to take 400 from each is to have the switch on both.... so why pay for the complexity?And why think about switching. Power boaters and large sailboat's with diesels must so they are sure to always be able to start the motor (and charge the banks back up with the alternator) Just a thought. I could be wrong. I ended up just making one bank on my last boat for this reason after much thought and planning for two.

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