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Old 05-13-2015, 10:53 AM   #1
Trawlerpeople's Avatar
City: Midland
Country: Canada
Vessel Name: Gipsy Queen
Vessel Model: Gavin Summerhill 29
Join Date: Aug 2013
Posts: 18
Charging mystery finally solved

We have owned our boat since Aug of 2013 and enjoyed many day trips with only one night on the hook. The po told me the charging system on our trawler was designed to recharge the entire double house bank (parallel setup) plus the 8D starting battery while underway without assistance from shore power. With our limited use away from shore power, I never really saw that this system performed as advertised. During this springs system checks we noticed arcing from a loose alternator connector and then the tach quit. This prompted a visit from the marina electrical guru who found the system was not working at all and with our habits being short trips out (a day or so) followed by shore power charging, we were actually camoflaging the fact that the system was not working. It may have been faulty for awhile. The electrician pointed out that the only power the diesel needed all day was the original start in the morning which was no problem because the 8D had been shore power charged prior.
As recommended we had the alternator rebuilt and a new voltage regulator installed and for the first time found it charging each bank (2 banks) at 75 amps while underway! The result is that everything seems to work better now - even the gauges seem to work better and we arrive back home with all batteries fully charged just as the original owner suggested. I think they said it is a three or four?stage alternator, twin belts, 200 amp rating that only now seems to be pulling it's weight. The po told of many long cruises where he only had to run the engine for 3/4 of an hour each morning to top up the system after the night before. Our boat has no generator, but dual 12/110volt systems throughout.
This is likely not new to the more experienced members, but it may get some owners thinking , especially diesel owners who just do day trips as we were. Looks like we finally have the boat with all systems operating as intended. Now we just need a destination!

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Old 05-13-2015, 10:59 AM   #2
RT Firefly's Avatar
City: Slicker?
Country: Bumpkin?
Join Date: Oct 2007
Posts: 12,758
Mr.T. Good to hear. We had EXACTLY the same problem with a former boat and solved it exactly the same way (alternator rebuild). Journey on...

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Old 05-13-2015, 11:19 AM   #3
City: Carefree, Arizona
Country: usa
Vessel Name: sunchaser V
Vessel Model: DeFever 48
Join Date: Apr 2008
Posts: 8,077
Are you saying you idle your engine for 45 minutes each day to charge the batteries?
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Old 05-14-2015, 07:15 AM   #4
FF's Avatar
Join Date: Oct 2007
Posts: 19,749
An alternator can only create its rated output , they are not "smart"..

The smart voltage regulator is what keeps everything going.

A marine house battery smart V regulator is totally different in how it sees its task, from one for a start battery .

Sparking at the alt will instantly kill it as the load gets disconnected while it is putting out amps , which usually blows the diodes.

DO NOT turn off the battery switch while the alt. is charging.

Shut down the engine then shut it off , or you will need another alt. rebuild.
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Old 05-16-2015, 09:40 PM   #5
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City: Cape May, NJ and Englewood, FL
Country: USA
Vessel Name: Irish Lady
Join Date: Dec 2007
Posts: 2,810
Boats that only go from marina to marina or never leave the dock without the genny running can mask serious DC system problems like you found. Its good to exercise the battery storage capacity regularly to make sure it hasn't gone south.
1984 Monk 36 Hull #46
Currently southbound in Georgia.
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