Updating system with SARV3, alternators, & DAC

For all issues involving the Smart Alternator Regulators, V1, V2 and V3

Updating system with SARV3, alternators, & DAC

Postby LAdamo on Sat Jul 25, 2015 2:39 pm

I'm looking at an update to my "old school" charging system aboard my Valiant sailboat. The system currently consists of main diesel with self regulated 50amp alternator, 8kW diesel generator with self-regulated 50amp alternator, a 600 Ah Lifeline AGM #1 bank, a Grp27 Lifeline AGM #2 battery, a Xantrex LinkPro Monitor, an Isolator Eliminator, and one dreaded 1-Both-2 switch. My intention is to replace both alternators with Ample Power Alternators, add a single SAR-V3 plus a DAC, and re-wire per Ample Power guidelines such that #1 is a true house bank charged by either/both alternators and #2 is a true start bank without the 1-Both-2 switch.

I have a couple of questions before I proceed:

- Is the DAC appropriate with this system? It seems that is it really designed with twin engines in mind, and I read somewhere on the site that running only one engine at a time, as would normally be the case in my situation, could lead to pre-mature wear on the alternator. If it is not, what would be the recommendation? - leave the engine alternator alone since it is more likely to run for long periods anyway and concentrate on high output from the generator? - or plan to use the AC charger when running the generator and focus on a high output alternator for the engine? - replace both alternators and get (2) external regulators?

- What are the pro's and con's (besides having to run additional cable) of an isolated ground on the alternator?
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Re: Updating system with SARV3, alternators, & DAC

Postby Coulomb on Sat Jul 25, 2015 9:34 pm

The purpose of the DAC is to prevent field current going to an alternator which is not rotating. That would happen if you regulate an a main engine alternator and one on the genset. Since they won't always be running at the same time, the DAC is necessary.

Isolated ground alternators are most often used on metal boats where the electrical system is not connected to the hull. There's nothing wrong with using them otherwise. In fact, wiring the ground of two isolated alternators together at one point will reduce errors and noise.

Adding a high output alternator to a genset may result in overheating of the genset if it is inside a small sound enclosure. Upgrading the AC charger is a good choice, but look carefully at the output curves versus battery voltage.
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