Does my alternator charge battery at low RPM?

[poconojoe]

Hey, another electrical question. I did a search but couldnt find an answer.
2003 Bayliner 185 bow rider, 4.3 L Mercruser and alpha one drive. The alternator is a 70 amp.
so, here's the question: When crusing at low speed, which I like to do a lot, is my battery getting charged?
I remember hearing (with any engine) that you need to be at a certain rpm for any charging to occur.
Is this true? If so, at what rpm does my alternator "kick in"?

 

[Bondo]

Re: Does my alternator charge battery at low RPM?

Hey, another electrical question. I did a search but couldnt find an answer.
2003 Bayliner 185 bow rider, 4.3 L Mercruser and alpha one drive. The alternator is a 70 amp.
so, here's the question: When crusing at low speed, which I like to do a lot, is my battery getting charged?
I remember hearing (with any engine) that you need to be at a certain rpm for any charging to occur.
Is this true? If so, at what rpm does my alternator "kick in"?

Ayuh,.... Usually, when startin' my motor, Ya, ya gotta hit 1000 or so rpms, 'n the alternator comes onto line,...

Once on line, it stays chargin' til ya shut the motor off, even at 650/ 700 rpms idlin',...

 

[UncleWillie]

Re: Does my alternator charge battery at low RPM?

Ayuh,.... Usually, when startin' my motor, Ya, ya gotta hit 1000 or so rpms, 'n the alternator comes onto line,...
Once on line, it stays chargin' til ya shut the motor off, even at 650/ 700 rpms idlin',...

+1
Especially with an alternator.
The older Generators were not so good at charging at low RPMs.
If the voltage at the battery measures (with a hand meter) above ~13.8v, You are charging!
In reality you are going to see more than 14v(Good) or less than 13v(Bad).

 

[poconojoe]

Re: Does my alternator charge battery at low RPM?

Thanks guys! Come spring, I'll have to keep an eye on the volt meter. I guess that will give me an idea.

 

[agallant80]

Re: Does my alternator charge battery at low RPM?

You should look at your volt gauge. Some of them will read what is in the battery and some will read if the alternator is putting anything out. In my bayliner if I turn the key to on but don't start the motor the gauge will slightly go up but still be close to 0volts. I installed a digital gauge in the cabin that reads what is in the battery bank.

 

[alldodge]

Re: Does my alternator charge battery at low RPM?

You should look at your volt gauge. Some of them will read what is in the battery and some will read if the alternator is putting anything out. In my bayliner if I turn the key to on but don't start the motor the gauge will slightly go up but still be close to 0volts. I installed a digital gauge in the cabin that reads what is in the battery bank.

This looks more like corrosion/bad connection issue.

Edit: and agree with others

 

[agallant80]

Re: Does my alternator charge battery at low RPM?

This looks more like corrosion/bad connection issue.

Edit: and agree with others

My boat is brand new. If I start the boat it reads what the alternator is putting out. Some reason it does not read what is in the bank only what the alternator is putting out.

 

[poconojoe]

Re: Does my alternator charge battery at low RPM?

It sounds like it would be a good idea to install a battery meter too.

 

[gm280]

Re: Does my alternator charge battery at low RPM?

Contrary to what a lot of folks think, an alternator outputs a voltage/current any time it is turning (if field voltage is present). The issue is, is it putting out enough output to charge your battery? That is where higher RPM's come into play. And that could be at a different RPM depending on the condition of your battery and anything else drawing power from it.

 

[alldodge]

Re: Does my alternator charge battery at low RPM?

My boat is brand new. If I start the boat it reads what the alternator is putting out. Some reason it does not read what is in the bank only what the alternator is putting out.

I know, and don't want to hijack the thread with a different issue(s) but, meters have enough impedance to be able to read a voltage. While digital meters have a higher impedance, the basics of analog vs digital would not be off by 12V, maybe 1 to 2V over a distance. Case in point, my Rinker meter read pretty much correct for many years. A few years ago I noticed it started reading around 12 to 13V depending on rpm and load. Put my hand held digital across the same terminals it reads 13.5 to 14.5V. An analog meter would not be that far off from a digital unless there is something else going on, meter corrosion, wires, connections, etc.

 

[Splat]

Re: Does my alternator charge battery at low RPM?

There is no way to read what the alternator is putting out vs. Battery voltage. Once the circuit is alive it's all the same unless you disconnect the alternator, or momentarily collapse it's charging field.

Once your alternator is going the only reading available is that of the entire circuit. Barring poor wiring and voltage drop.

 

[agallant80]

Re: Does my alternator charge battery at low RPM?

Its bayliner. They do strange things. I am thinking they hooked it up to the alternator where the diods could prevent it from reading back in to the bank. It seams that they did it so you would know if your alternator was working or not. poconojoe, when you turn your key to on but the motor is not running does your voltage gauge show anything?

 

[poconojoe]

Re: Does my alternator charge battery at low RPM?

Its bayliner. They do strange things. I am thinking they hooked it up to the alternator where the diods could prevent it from reading back in to the bank. It seams that they did it so you would know if your alternator was working or not. poconojoe, when you turn your key to on but the motor is not running does your voltage gauge show anything?

With all the talk here, I too was wondering what the volt gauge would show with ignition on/engine off. Can't check it right now. I apologize for that. Boat is in my garage and batteries are in the basement on a trickle. Had knee surgery and I don't think I should be lifting a battery for a while.
When I'm up to it, I'll check it out and report back.
Thanks all!

 

[bruceb58]

Re: Does my alternator charge battery at low RPM?

With all the talk here, I too was wondering what the volt gauge would show with ignition on/engine off.

12.6V with a fully charged battery.

May read lower if there is voltage drop between the battery and the ignition switch(where the gauge is usually connected).