Cruisers Forum

Join CruisersForum Today

  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
Thread Tools Search this Thread Rate Thread Display Modes
Old 08-03-2013, 11:32   #1
Registered User

Join Date: Aug 2012
Location: California Central Coast
Boat: Pacific Seacraft, Dana, 24
Posts: 81
Send a message via ICQ to EveningTide
Atomic 4 voltage regulation

A friend has a Cal 28 with an Atomic 4 motor. The motor is a rebuilt, installed two year ago and the alternator is also rebuilt. The motor was slow cranking and we had to use a shore battery charger for 15 minutes to raise the battery voltage to the point that the motor would start. After it had run 10 minutes I noticed that the battery voltage read 13.4 volts. I checked with my multimeter and got the same reading. Changing the RPM did not affect the voltage at all- it seems the regulator is set at 13.4 volts. This voltage seems about right for float charging but would be way too low if you wanted to fully charge a battery that had been significantly discharged. This boat is used as a day-sailor and there is very little electrical load when sailing so the batteries will rarely get discharged. Could the alternator purposely have been set to float the batteries rather than overcharge them? Is this how they did it back in the Atomic 4 days? Comments, please.
EveningTide is offline   Reply With Quote
Old 08-03-2013, 11:39   #2
Registered User

Join Date: Dec 2008
Location: Oriental, NC
Boat: Mainship Pilot 34
Posts: 1,461
Re: Atomic 4 voltage regulation

Most alternators even today have a simple, single voltage regulator set to supply 13.5 to 14.0 volts. It sounds like your alternator is doing what it is supposed to.

I would hook up the shore power charger to the batteries once in a while to bring them up to fully charged status.

djmarchand is offline   Reply With Quote
Old 08-03-2013, 16:15   #3
Registered User
S/V Alchemy's Avatar

Join Date: May 2008
Location: Toronto
Boat: Custom 41' Steel Pilothouse Cutter
Posts: 4,965
Re: Atomic 4 voltage regulation

You need to either swap out the internal regulation or consider external regulation. Then you can charge the batteries at set points you determine.

Of course, if you have the stock 35 amp Motorola or Delco alternators, you're not going to charge anything particularly quickly. I think of the alternator on a direct-drive Atomic 4 as being fit to run nav lights under motor at night, and not a whole lot else.

You can always shorten and "up gauge" your wiring, too, to get maximum pop out of the juice you are making, but I would say if you have charging issues, go to a pair of Group 27s or even Group 31s, upsize to a 55 amp alt, and monitor state of charge with some sort of regulation when 14.2 needs to go to 13.4 or whatever equals "float" on this boat.
Can't sleep? Read for fast relief. Can't read? Avoid, because it's just personal reviews of sea books.
S/V Alchemy is offline   Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 19:37.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.