Alternator output 13.5V

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SEMPERAVANTI41

SEMPERAVANTI41

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Jun 15, 2012
717
BAVARIA C57 Greenport, NY
The manual for my Hitachi 80 amp alternator on my Yanmar engine shows a maximum regulated output voltage of 13.5 volts. The voltmeter on my boat confirms this value. I have a 345 amp hour house battery bank and a dedicated starting battery. The starting battery will normally indicate a higher voltage than the house batteries.

Why is the maximum voltage so low? My built in battery charger which has a temp. sensor charges at 14.3 volts. Would it be possible & wise to raise the alternators charging voltage?
 
Bill Roosa

Bill Roosa

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Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
Does it have an external 3 stage regulator? I'm thinking not. Auto style regulators expect the motor to be on any time there are loads on the batteries. It has a momentary (1-2 min) "fast charge" of 14.4 then goes back to trickle charge mode so it does not over charge (the motor is ALWAYS ON in it tiny little brain) the batteries. After all it has at least a half hour to put the juice back in that the starter took out.
The good news is with 80 amps you should be good as long as you leave the motor running. Most boats don't have 80+ amp drawn from the batts EVER so it should be able to meet all your needs (as long as you leave the motor on)

Seriously, it needs a 3-stage charger designed to recharge (not trickle charge) deep cycle (not auto style) batteries.
 
SEMPERAVANTI41

SEMPERAVANTI41

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Jun 15, 2012
717
BAVARIA C57 Greenport, NY
My Hitachi alternator has a internal voltage regulator. I am trying to find out why the regulated voltage is capped at 13.5 volts.
 
Gunni

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
SEMPERAVANTI41 said:
The manual for my Hitachi 80 amp alternator on my Yanmar engine shows a maximum regulated output voltage of 13.5 volts. The voltmeter on my boat confirms this value. I have a 345 amp hour house battery bank and a dedicated starting battery. The starting battery will normally indicate a higher voltage than the house batteries.

Why is the maximum voltage so low? My built in battery charger which has a temp. sensor charges at 14.3 volts. Would it be possible & wise to raise the alternators charging voltage?
Click to expand
Have the same alternator, and a similar Ah house. My house battery seems to settle into the 12.5 vdc range as soon as we pull the dock power and switch on the house load. Same thing when we shut down the aux when underway. This is read direct at the battery via a Link battery monitor. Multiple batteries, multiple connections, multiple resistance has been my assumption.


Don't think you want more than 13.5 vdc going to a multi-battery house bank unless you also have it temp regulated.
 
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