Joerg,

That's what I thought when you first started having overheat alarms in your 55 battery area. The Mastervolt alternator is continuing to charge, already charged batteries, causing heat in the battery area. Pochon's suggestion to change the regulator is logical, but I am surprised that they did not check the voltage at the bank and at the regulator to ensure that they were the same.

I am not an electrician: My guess is that either the regulator settings are wrong, the regulator is defective, or there is resistance in the wire and connections between the actual battery bank and the regulator, which is lowering the voltage "seen" by the regulator and "fooling" the regulator to continue charging. 

My non-electrician suggestion: It will be a tedious process checking between both. I believe that you will find the most likely connections near and on the excite relay for the alternator. loosen each connection and use CorrosionX before retightening. Make sure that any crimp connectors are done correctly and have crimped the entire wire, replace any suspects. Check voltage often during the process so that you'll know when you have found and corrected the resistance problem.

As an alternative and temporary patch, maybe you could lower the charged voltage setting at the regulator by 2.5 volts.

Best,

CW Bill Rouse

Yacht School (formerly Amel School) - Supporting Amel Owners

720 Winnie St

Galveston Island, TX 77550

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On Wed, Jul 3, 2019 at 12:25 PM Joerg Esdorn via Groups.Io <jhe1313=yahoo.com@groups.io> wrote:

On my 55, I have a 110A/24v Mastervolt alternator for the house bank and the alpha pro regulator.  I’ve had the battery temp alarm come on several times now because the regulator does not switch from Bulk to absorption.  On my voltmeter on the panel, voltage is 30-31V and charge rate goes up and down quickly from 10-40A, all with the batteries full after days on shore charger.   I checked out the regulator with the Masteradjust software and the sense and battery voltage was just below the 28.5V for the switch to absorption.   So the regulator is seeing 2-2.5V less than what the batteries have - I checked the voltmeter with my multitester.   At the suggestion of Pochon, I just replaced the regulator but that wasn’t the problem. 
Any idea what could be wrong would be much app!   

Joerg Esdorn
A55 Kincsem
just left Barcelona for Valencia