Quote Originally Posted by mmandley View Post
Bro honestly letting the boat idle isnt going to help much, an alternator is really barley putting any power out at idle.
It needs to be at 2K RPM to reach max output.

SO if you try the same thing with your new alternator their is a good chance you will toast it in time as well.

NOt trying to rag bro honest. I like your upgrade, and its a value added one but if you tie up and crank that long, you need to look into golf cart battery upgrades.

Mike are rated at 20amp for 570 minutes each
70amps for 180 minutes each <if i recall>

I have ran mine all day with the tunes about 1/2 and never an issue but i do have to shore charge them because my boat cant get them to max that fast
I’m not sure I completely understand. Here’s my thought process:

The alternator converts energy from mechanical to electrical. The mechanical energy is supplied from the engine, whose input is chemical energy in the form of gasoline. The electrical output power of the alternator must be less than the mechanical input power from the engine, which must be less than the chemical power from gasoline combustion.

The alternator's maximum output power requires maximum engine speed & max fuel consumption. Now fortunately, alternators are equipped w/ regulators which provide constant voltage operation, by selectively adjusting the field current, the magnetic field strength can be varied & consequently a regulated output can be achieved despite varying loading & engine speed.

If the engine is idling under light load, the regulator will adjust the field current for the needed load power w/ constant voltage, approx. 13.8V. If the load is then increased, the voltage out momentarily droops, so the field current is raised by the regulator. The voltage at the alternator output increases to the right value, & the new current value is obtained. But the power has increased as well. This increase in electrical power mandates a corresponding increase in mechanical power from the engine.

If the fuel consumption is constant, i.e. no increase in fuel, than the idle speed will drop. Since the fuel consumed at the original engine idle speed did not increase, & the alternator demands more mechanical power from the engine, the engine must lose some of its mechanical power. The rpm drops as a result but the power out remains the same. Not sure how more engine rpms will make a difference unless your alternator is causing your engine to stall.

I would have to imagine that your factory alternator is sized such that it’s max output is enough to keep up with all demand even at idle. Add more demand though and I would say no matter how many batteries you have if your alternator is undersized ie max output power can’t keep up with demand you are in trouble as no matter the rpm it’s going to be running all out to keep up?

I’m in the same “boat” as you guys hope I don’t need to replace the alternator?