External vs Internal Regulator

[john61ct]

If you were to bother upfitting an external VR, then it should be adjustable voltage.

Many bank types need a specific setpoint, there is no one size fits all.

[ben39]

I don't know where you are cruising, which ambient temperature?
What internal regulators many times missing is temperature compensation, because no temperature sensor at the battery mounted.
If you cruise in the tropics very important. So an external regulator should have always a temperature sensor mounted at the batteries.

If you are a sailor you have the risk of overcharging the batteries.
For example: You are on the engine and your regulator is already from bulk to acceptance mode to float mode.
You stop the engine, because you think there is enough wind for sailing.
But 10 minutes later you start the engine again.

Regulator stays in acceptance mode on a fixed time based setting and was already in float.
At the time of restarting the engine regulator goes to bulk and AGAIN to the long acceptance mode, before going to float. At this point you have the risk off overcharging and damage your batteries, especially AGM, wet cell loss only some more water.

I just post my experience about the regulator I am using in another blog:
Arduino based Alternator Regulator Project - Cruisers & Sailing Forums

This regulator monitors also the amps. If the amps in acceptance mode are very low, means batteries are full, regulator switch to float mode. AND don't stay to long in Acceptance mode

So if you buy a external alternator controller, look for one that also ""read"" the amps that goes into the battery, your battery is more protected for overcharging.

Another protection on a external regulator is protecting from the alternator for overheating, with a temperature sensor on the alternator for regulation.