I have a similar setup on my cat. It came with twin Yanmars which
have simple alternators with internal regulators. I replaced one
alternator with a high output, regulated by a 2000R regulator. It
would, on occasion run the output voltage up to 17 V until I figured
out what was happening.

The high output alternator was still connected directly to the
starting battery. When the battery combiner latched everything
together, it worked fine. But if the connection parameters weren't
met, the regulator sense was seeing the house bank, but the output was
going to the starter battery. This mismatch could permit overcharging.

The solution was to reroute the output only to the house bank, and
feed the starter battery only through the combiner. Recently, I added
an EchoCharge, and had to reroute the other alternator output. All
charge sources are now directly (more or less) to the house bank,
while the starter batteries are isolated by the EchoCharge, and the
normal connection between the starters and their alternators is severed.



Mic wrote:
Maybe you have a suggestion:

Situation:

A Cat with 2 engines and 2 alternators

"Yes, it is an external regulator, a NextStep. Which works just fine
with both engines going, it is only when the port engine is running by

itself that it overcharges. There must be a problem with the wiring
somewhere that I just can't find. Also, we have 5 gel cell batteries
and they all seem to be fine."

I believe the Parallel Solenoid has been replaced.

This is not my boat but is an issues with someone elses, any
suggestions, the only info. that I have is the above, so a Q and A
does not apply.....

TIA