High alternator output - Bav 44, D2-55 engine

[Wavegoodbye]

Sirs, advice sought
After starting my engine I tested the alternator output to the starter battery and it was up at 15.1v.
The lead from the alternator to splitter is showing 15.1v as well. The house bank we’re not receiving a charge as they are at 13.1v
I want to install gel type batteries as the house bank, continue to use a lead/acid battery for starting duties and don’t want to risk overcharging or cooking the batteries on a long motor-sail. The boat is in Latin American Caribbean waters With high ambient temperatures
Can you help please

[tiger79]

It sounds as if the splitter is faulty, which means that the alternator can't sense the battery voltage correctly, so is increasing the charge voltage.

If you swap the start battery and house battery connections on the splitter, it will help you to diagnose what's wrong.

[IslandAlchemy]

Replace the splitter with a VSR.  Even if the splitter isn't faulty, it will reduce the voltage drop.

[tiger79]

Replace the splitter with a VSR.  Even if the splitter isn't faulty, it will reduce the voltage drop.

Not necessarily.  For many years, Bavaria have been fitting low-loss splitters with virtually no voltage drop.

[JEN-et-ROSS]

Does the alternator have a 'sense' input connected to the battery bank..?
Many marine alternators have this, automotive ones tend not to need this as the battery is very close to the alternator and therefore voltage loss is very low.
i.e. a connection that 'senses' the voltage at the battery bank and allows the alternator to compensate for a voltage drop caused by splitters or very long cable runs.
Is it possible that you're losing a Volt or so at the splitter and more loss in the cable run or multiple connections between the battery bank and the alternator?
If so, the alternator may simply require to supply 15.1v to ensure that a 13.1v 'float' charge is delivered to the battery bank.............Bill.

[JoAnn]

I recently had the same problem.  My issue was that the splitter failed when I inadvertently ran the bow thruster with a dud battery set (my fault) and it tried to draw to much current via the splitter.  The splitter had three battery outputs Starter, House, and Bow Thruster.  The House and Bow Thruster failed but the Feed to the Starter battery kept working.  The Alternator has a seperate field (sensor) wire direct to the House Batteries to determine the required output.  Since the House batteries were not receiving any alternator current it was showing 13.6 volts (I was in marina and they were fully charged) and the alternator was trying to compensate by increasing output which was going the starter motor only, 15.1 volts.  Momentarily connecting house battery feed with starter battery feed corrected the alternator output voltage as a check of where the problem may of been. Replacing the splitter, with like for like, permanently fixed it for me.

[Wavegoodbye]

Hi fellow owners, I found a loose connection between batteries and alternator (yellow sensing wire - all is well now
Thank you for your time, advise and support  😁