• Mobile App For Android Now Online!

    Download it here. The app is searchable in the Google Play Store under Sailboat Owners.

    Sorry iPhone/iPad users, we are still waiting on Apple. :(

    Click the X in the upper right corner to make this go away

Making Sense of Automatic Charging Relays

Feb 26, 2004
21,702
Catalina 34 224 Maple Bay, BC, Canada
Nice update.

One thing to add:

I have found many folks misunderstand charging because they are used to being plugged into shore power, and, thus, leave their docks with full house banks.

It is critical to revise the thinking FROM: "I start with a full house" (pi:)) TO: "I've been at anchor for a night or two, and my house bank is (partially) depleted." The house bank should get priority, right?

It's just another reason to want/need to run charging sources to the house bank, since as MS wrote, the start bank is still over 99% full after starting your engine.

What is also truly helpful about this article is the MYTHS he busts wide open. Funny how important this is, and combiners have been around for over 20 years!!! I know, because I installed my Yandina combiner in 1998 when I first bought my boat.
 
  • Like
Likes: Ward H
Apr 7, 2016
184
Beneteau First 305 Seward, Alaska
I wish I could press like 100 times. Thanks for all your hard work. Your posts and website have helped me a lot this past year or so.

Juice
 
Feb 6, 1998
11,414
Canadian Sailcraft 36T Casco Bay, ME
It is critical to revise the thinking FROM: "I start with a full house" (pi:)) TO: "I've been at anchor for a night or two, and my house bank is (partially) depleted." The house bank should get priority, right?
It's all about charging performance and the fact that routing all charging to the start battery first results in multiples more terminations all leading to voltage drop and lower charge performance for the house bank. Also the risk of relay cycling and pushing a VSR at its limit, rather than coasting along not needing to work very hard. It's all in there...
 
Apr 7, 2016
184
Beneteau First 305 Seward, Alaska
It's all about charging performance and the fact that routing all charging to the start battery first results in multiples more terminations all leading to voltage drop and lower charge performance for the house bank. Also the risk of relay cycling and pushing a VSR at its limit, rather than coasting along not needing to work very hard. It's all in there...
The video you did explains it all.
 
Feb 13, 2011
3
Cal Jensen 29-2 St. Petersburg
I realize this is an older discussion but I need some insight on upgrading my sailboat's alternator....
I took my 30 year old 51Amp Motorola alternator into the repair shop to have it's output checked and after testing was told that it was no longer working as I had suspected. I think that this was due to my incorrectly reattaching the wires to the alternator's terminals due to the wiring diagram I was using from the owner's manual. The color of the wires in the diagram did not match the wiring harness going to the alternator.
I had switched from wet cell deep cycle marine batteries to two AGM deep cycle batteries because I was thinking that they would give me longer discharge time and better performance. However, I had to pull in to a marina each night when motorsailing on a cruise to plug into shore power to keep my AGM's fully charged with the onboard 120V charging system. I noticed that the battery voltage indicators showed 13.8V on both batteries and never got to 14 volts.
So now I have to replace the old Motorola 51A alternator and the alternator shop is selling me a Balmar 70V alternator...not sure which series...but it will fit my Universal diesel without modifying the mount or the single pulley...
My question is: should I purchase an external voltage regulator for my application? The Balmar alternator has only two output terminals, B+ and tach sense...I'm not sure where to connect the other wires that used to connect to the internal voltage regulator of the Motorola alternator. One for Exc, one for Sense, and one for ignition.
 
Feb 6, 1998
11,414
Canadian Sailcraft 36T Casco Bay, ME
I realize this is an older discussion but I need some insight on upgrading my sailboat's alternator....
I took my 30 year old 51Amp Motorola alternator into the repair shop to have it's output checked and after testing was told that it was no longer working as I had suspected. I think that this was due to my incorrectly reattaching the wires to the alternator's terminals due to the wiring diagram I was using from the owner's manual. The color of the wires in the diagram did not match the wiring harness going to the alternator.
I had switched from wet cell deep cycle marine batteries to two AGM deep cycle batteries because I was thinking that they would give me longer discharge time and better performance. However, I had to pull in to a marina each night when motorsailing on a cruise to plug into shore power to keep my AGM's fully charged with the onboard 120V charging system. I noticed that the battery voltage indicators showed 13.8V on both batteries and never got to 14 volts.
So now I have to replace the old Motorola 51A alternator and the alternator shop is selling me a Balmar 70V alternator...not sure which series...but it will fit my Universal diesel without modifying the mount or the single pulley...
My question is: should I purchase an external voltage regulator for my application? The Balmar alternator has only two output terminals, B+ and tach sense...I'm not sure where to connect the other wires that used to connect to the internal voltage regulator of the Motorola alternator. One for Exc, one for Sense, and one for ignition.
Check the link below. You'll find many Motorola / Leece-Neville specific externally regulated alternator options and the lowest prices anywhere on externally regulated alternators. There's also a custom built 72A version of the original 51A alternator you had (which was long ago discontinued) and that alterntor is availble to order as an internal or external regulator. With AGM batteries you'll want external regulation.

CMI / AMP-IT Alternators (LINK)

The best deal going is an AMP-IT 72-ER paired with a Wakespeed WS100 regulator. The WS100 includes both the alternator and the battery temp sensors (critical with AGM batteries).

.