Solar and Alternator

[jwag956]

I feel like the more I read about alternators, the more confused I get.
I have a standard internal-regulated alternator and a SunSaver6.
The SunSaver6 is connected directly to the battery as is the alternator.

I keep reading (but not understanding) that alternators 'detect' voltage and de-rate theirs or actually stop charging.

Would having the solar active while underway actually cause the alternator to not charge the battery?

I have some anecdotal evidence that sometimes it appears to (in that after a couple hours of cruising, my battery is fairly depleted (sorry - didn't write down the voltage).

 

[DavidM]

Your internally regulated alternator produces a fixed voltage, usually about 14.0 volts. The SunSaver solar controller produces a voltage that is dependent on the current it is providing to the batteries. When the battery voltage gets above 14.0 volts, the alternator will produce little charging current. But the SunSaver will continue to charge at a current depending on the solar panels connected and the battery's ability to accept that current.

In other words, both the altenator and the SunSaver work together to charge the battery until the battery voltage gets above 14.0 volts then it is only the Sunsaver.

David

 

[Jeff F]

I agree that solar shouldn't interfere with the alternator's ability to provide a healthy charge and manage house loads.

I'd check to see if the alternator is working. Closely monitoring the voltage will likely give lots of further clues.

 

[rslifkin]

DavidM's description is dead on. With my internally regulated alternators, if I start in the morning with the batteries down a bit, both solar and alternator will feed power. If there's enough sun to push the batteries up to absorb voltage with the loads while running, the alternators just take a nap once the solar gets the voltage above whatever the alternators are aiming for at the time. Once the solar drops to float, the alternator voltage is generally a bit higher than the solar float, so the alternators wake back up and supply power while the solar sits around and does nothing.