6 Amp Alternator charging how much.

Stu Jackson · Apr 18, 2009

It'll put out 6 amps until the battery bank

is around 85% full until the battery bank acceptance will begin to seriously restrict the amount of charge that the battery will, uhm, accept. That's why they call it that. See: http://c34.org/bbs/index.php/topic,4787.0.html

Maine Sail · Apr 18, 2009

Stu is right

Stu is right but there is one more point. It will put out a max of 6 amps when cold. As the alternator heats up it may put out less than it's rated face value.

Let's say you get 5 amps hot.

-75 amps drawn off the bank / bank is 175 amps / 85% of 175 ah's is 148 ah's/ 48 amps is what will get you back to 85% state of charge / It will take you roughly ten hours at 5 amps to get back to 85% state of charge the rest could take you more than ten hours to reach 100% SC....

Hope that made sense..?

Warren Milberg · Apr 19, 2009

Jack:
Don't want to rain on your parade, but be aware that most small solar panels suitable for a boat your size (say 5-10 watt output or so) are really battery maintainers, not chargers. If you get a larger output model that could provide charging, (1) they tend to get expensive, and (2) you'll need a voltage regulator. I use a 5-watt ICP solar panel to maintain my batteries, but I keep them charged with built-in charger.

sailingdog · Apr 19, 2009

Jack—

I'd recommend you read this primer on solar power for boats I wrote a while back.

jackhartjr said:
Maine Sail, that was perfect!
I had been on several boards and asked that question.
Thanks to you and Stu!
Jack
PS...guess I better start looking at those solar panels a little closer! The good news is with a 22 foot boat, not a lot of 'toys on it and planning to put LED lights throughout including reading lights...we won't have a lot of power needs.

Bill Roosa · Apr 19, 2009

What are the loads?

Since you have a smaller boat with fewer loads then you should not need to discharge the battery that deeply.
Also, if you are just weekending it then the battery charger could be your primary means of keeping the batteries charged up. As a cruising setup you are going to get frustrated without some additional source of electrical energy with out a doubt. Id be thinking wind personally but it really depends on how you use your loads and motor and the size of the battery bank.

Ron20324 · Apr 19, 2009

Also not wanting to rain on your parade, but most outboards I've seen have only a 12-volt output (at your 6 amps in this case). You can't charge at that voltage unless your batteries are less than that. Even my Honda 2000 generator only puts out 12 volts- barely a maintenance charge.

MoonSailer · Apr 19, 2009

Add a Battery!!!! The cheapest thing to do is add another battery. Two of three batteries should be enough for a weekend or longer. A small solar and running the outboard would just extend it a little. But if you figure during aweek you would run the outboard 6 hours you would get about 30 amp hours ..enough to run the anchor light 3 nights.!!!!

Benny · Apr 20, 2009

I have some experience with power systems on a 22' boat. It is just not practical for space and weight considerations to install more than two batteries. A couple of group 27 wet cell, deep cycle will provide you around 200 amp capacity. Gas generators, solar panels and wind generators are just two expensive and cumbersome to install in a boat your size. Your alternative is to recharge your batteries with a shore power plug-in electric battery charger. It is not good for the life of wet cell batteries to deplete them more than 50% of its capacity so that may leave you with about 100 usable amps between recharges. A 20 amp battery charger will recharge them batteries back to 100% charge in about 9 hours. You can do it 2 ways take the batteries out of the boat and recharge them at home or take the boat to a marina slip and recharge them there. A boat on a trailer can be parked near an electrical outlet but a boat on a mooring would be limited. A 20 amp three cycle charger can be purchased at any discount store for around $50. We do some cruising on a 22' boat every year and we time stays at marina slips to enjoy hot showers and ammenities plus to recharge our batteries. The alternator on your outboard was designed to power navigation lights and not to recharge batteries. It probably lacks the "umph" in voltage to push the charge into the battery. Conduct a power survey so you'll know your consumption and your need to recharge intervals. Good luck.

MoonSailer · Apr 20, 2009

You can also use your tow vehicle to recharge your batteries. Use battery cables connected to the discharged batteries and run your car or truck . Two batteries were usually enough for me over a weekend. I guess that you need a volt meter and use it to check the voltage output of your outboard. With simple systems it is RPM dependent where higher RPMs gives a higher voltage. Voltage will determine the amps going through the battery. A given voltage will produce a given amperage moving through a given resistence.

sailingdog · Apr 20, 2009

You'd have to run the engine on your tow vehicle a long time to really recharge the batteries.

MoonSailer said:
You can also use your tow vehicle to recharge your batteries. Use battery cables connected to the discharged batteries and run your car or truck . Two batteries were usually enough for me over a weekend. I guess that you need a volt meter and use it to check the voltage output of your outboard. With simple systems it is RPM dependent where higher RPMs gives a higher voltage. Voltage will determine the amps going through the battery. A given voltage will produce a given amperage moving through a given resistence.

MoonSailer · Apr 20, 2009

Many vehicles have 100 amp alternators and if hooked up to two batteries you could get a substantial charge in an hour or so. You could also drive somewhere to get dinner or groceries etc during the charge time. You could do just the bulk charge phase and leave the 100% charge till later using a plug in charger at home. We are not talking ideal routine here we are talking out for a week and wanting to put some juice in the batteries.