Alternator Overcharging Batteries?

[kenbo]

Originally Posted by john61ct

I read "built that way" as referring to the full "just put out a set voltage then cut back when the alternator heats up" in #2, rather than temp compensation / protection in general

The way most internal voltage regulators that have temperature compensation work is to apply either a reduction (hot) or increase (cold) to the Vset of the regulator.

In more sophisticated voltage regulators, temperature protection of the alternator is done by reducing or capping the field current resulting in a depowering of the alternator thereby reducing the internal heat produced by the stator and bridge rectifier. The Vset would remain controlled by the temperature of the battery not the alternator, or more specifically, the voltage regulator.

[kenbo]

Originally Posted by sailinglegend

My expensive hot rated Balmar 6 series alternator has temperature compensation so after half an hour is down from 14.4v to below 14 volts.

It's set up on a two-way switch so if the external regulator fails you switch to the internal regulator.

Your expensive hot rated Balmar 6 Series is a Delco CS144. It's internal voltage regulator has temperature compensation as far as I know unless Balmar had a custom one made without it. Possible but not likely.

[Stillwater1]

Well. So much to think about. Thanks to you all for your answers.
Further info. The trip the other day was not what normally happens with the boat. She sails and only uses the Yanmar to get into or out of a slip or to the fuel dock. I run it once a week for 20-30minutes at 2000 rpm as a maintenance thing. She is charging at 14 volts, that does not seem to change ever.
The solar panel charges the batteries at the proper voltage requirements (14.5 for absorption, 13.2 float) and is the main charging device now. Over the past week the batteries have been at between 90 and 100% SOC. So I am not gonna worry too much for now.

[Maine Sail]

Originally Posted by kenbo

Your expensive hot rated Balmar 6 Series is a Delco CS144. It's internal voltage regulator has temperature compensation as far as I know unless Balmar had a custom one made without it. Possible but not likely.

The 6-Series is based on the CS130D platform with a custom DE frame and rear frame plus Balmar's own internal components including stators, rotors, rectifiers, rectifier isolators etc....