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  #1  
Old 12-18-2012
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Charging batteries

I bought a 1996 Gemini 105M. I have it on a mooring buoy not at the dock. My alternator is only putting about 12.5 v. It took 25 hours of using the engine in my way from Georgia to Miami to bring it to 14.0.
I have 2 banks of batteries. I have three Seavolt AGM's, one group 24 and two size 8D. I am totally ignorant about the boat electrical system, but I know that not being able to hook up to shore power, will eventually discharge my batteries. I have a new Honda EU1000i generator and I was wondering how to charge at least my starting battery. I do not know which battery is the starting battery, but I am assuming is the group 24. Do I connect the generator directly to the battery or do I use a a battery charger connected to the generator. The boat has a Xentrex Freedom HF 1800 inverter/charger. Do I turn it off when I connect the generator to the battery
Any suggestions will be welcome. I also would like some suggestions as to some basic boat electrical system books.
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Old 12-18-2012
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Re: Charging batteries

Being that your batteries eventually reach 14v, your alternator is probable putting out its maximum but chances are your alternator has a very low output (amps) a higher amp alternator will shorten that charging time a lot.
Your generator only has about an 8amp dc output so direct connection to the batteries would take forever.

Last edited by cruisingdream; 12-18-2012 at 11:12 PM.
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Old 12-18-2012
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Re: Charging batteries

You should consider getting that alternator tested. It should be putting out ~14VDC. Amps will vary with the model (HO, etc) but you should be able to top off your battery bank within 30-45 mins without issue.

To answer your question regarding the generator, you would need a 12-14V DC output from the generator to directly connect to your battery. I do believe the Honda 1K has the output capability but may use a proprietary connection. I dont think it is necessary to turn off the inverter when charging directly. Without a DC output or connectivity you would have no other option but to connect to an AC battery charger. Keep in mind, in either case, your amperage load will be limited with the small Honda genny and may take some time to charge fully.
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Old 12-19-2012
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Re: Charging batteries

This information should assist.

• View topic - E Bay Solar Panels
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Old 12-19-2012
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Re: Charging batteries

I second the recommendation of a solar panel. I installed a simple 40 watt panel with a controller and in-line fuse to keep my batteries charged. Seems to work great.
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Old 12-19-2012
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Re: Charging batteries

Welcome to the world of Gemini's! My previous boat was a 2007 105MC, Hull 987.

Your Westerbeake alternator should be putting out 14.1v, it's a standard 55 amp alternator, which means at idle it's only really dumping 20amps. You need to get it checked.

Gemini's don't come with chargers, but I'll assume the previous owner put at least a 20amp onboard. If he did, and it's working you should plug your Honda directly to the 30 amp plug and use it to power your charger, that is the most efficient way to use your Honda as the 12v outlet only puts out 8 amps.

If you have not done so yet join the Gemini Cat's group at yahoo, great information.
Yahoo! Groups

If you have davits you should look at hanging at least a 125w panel between them, it's not hard to do and the benefits are outstanding. You can also put it on the dog house roof (simpler install) - then pull the boom to the side with the traveler so it gets good sun. A solar panel is the only way you are going to be able to keep those AGM's topped off and AGM's need to be charged to 100% periodically or the die a premature death.

Your batteries should be on two shelves, the upper shelf is likely the group 24 starting battery and the 8d's on the bottom (that's a lot of weight on the port side by the way).
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Old 12-19-2012
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Re: Charging batteries

Quote:
Originally Posted by nmejicano View Post
My alternator is only putting about 12.5 v. It took 25 hours of using the engine in my way from Georgia to Miami to bring it to 14.0.
This could have a few causes.

#1 Poor factory wiring in alternator system leading to voltage drop. Could be bad connections, undersized wire or bad case ground on the alt.
#2 Diode isolators in system
#3 A bad diode in the alt giving you 1/3 or 2/3 the output.

To test this the alternator needs to be measured across the B+ terminal and ground. You then test the voltage at the battery bank. If the voltage at the back of the alternator is not within +/- .1V of the voltage at the battery bank then you have a voltage drop issue and this will drastically SLOW your charging. With bad enough voltage drop it can take 25+ hours to charge a bank and the voltage won't get to 14+ until the current is very low..

Quote:
Originally Posted by nmejicano View Post
I have 2 banks of batteries. I have three Seavolt AGM's, one group 24 and two size 8D. I am totally ignorant about the boat electrical system, but I know that not being able to hook up to shore power, will eventually discharge my batteries.

As others have mentioned you'll want to invest in solar. You can't keep AGM batteries sufficiently charged with an alternator.


Quote:
Originally Posted by nmejicano View Post
I have a new Honda EU1000i generator and I was wondering how to charge at least my starting battery. I do not know which battery is the starting battery, but I am assuming is the group 24. Do I connect the generator directly to the battery or do I use a a battery charger connected to the generator.

Battery charger connected to the generator.


Quote:
Originally Posted by nmejicano View Post
The boat has a Xentrex Freedom HF 1800 inverter/charger. Do I turn it off when I connect the generator to the battery.
No, you want to use that to charge the batteries. You may need to go into the set up and see if you can limit the current output so you don't overload the EU1000..


Quote:
Originally Posted by nmejicano View Post
I also would like some suggestions as to some basic boat electrical system books.

Charlie Wings book is one of the best. Easier for a novice to understand than Calder.. It's called "Boatowners Illustrated Electrical Handbook Second Eddition"..
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Old 12-19-2012
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Re: Charging batteries

The 12V output of the Honda EU1000i is unregulated, so you must monitor the charge state of the battery. For that reason, it's probably better to use a regulated charger.

If you do ever use the Honda's DC output, be sure to turn the Eco-Throttle OFF for maximum output and faster charging.

The DC charging cable (if you need one) has the correct perpendicular two-prong plug, two medium clamp-type clips, and is sold by any Honda dealer. Part Number is 32660-894-BCX12H and lists for $11.98.

Here are some links:

Honda Dealer Locator

Honda Accessories Catalog

-Robert@Honda
Caveat: I work for Honda, but the preceding is my opinion alone.
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Old 12-19-2012
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Re: Charging batteries

Listen to what MaineSail says.

AGM's can suck a lot of current so the 12.5V wouldn't be surprising if it rose more quickly. But if it takes 20+ hours to reach 14V you have some significant issues.

I would first inspect the wiring. A bad connection could be causing what you're seeing and is a simple fix. Like Mainsail says, the way to find this would be to measure voltage at the alternator and compare it to voltage at the battery.
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Old 12-19-2012
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Re: Charging batteries

Thank you all for all your input. I have just bought a Honda EU2000i and I got an adapter from West Marine 15A male to 30amp female. I am also planing on installing solar panels next year. The boat is already wired (2012) for solar and wind, so other than water, I hope to be energy independent. I can also use the little Honda generator for emergency power at home during the hurricane season. Very much appreciate yourinput. Have a nice Holiday season.
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