Monday, January 3, 2011

Another little project (2)

Another in a long series of projects.  I wonder when I benefit from all this work and start to experience the advertisers picture of sailing: sitting back with a drink in hand as the boat heads off into the sunset?  More on this later...

I've just finished installing a new alternator.  The boat came with a Hitachi 80amp alternator, with an internal regulator.  For those of you not into the depths of DC charging, I'll try to keep this part brief.  Although discussing alternators in a non-DC nerd way is difficult.  You may want to skip ahead to the photo and then move on.

I never saw the old Hitachi charge at anything over 13.4 volts.  This is way too low for a decent charge.  Its perhaps ok for an automotive charger which only has to run the accessories and restore the charge the start of the engine took out of the battery.  In a sailboat which may run its batteries down a lot since the engine was last turned on, you want the engine alternator to produce the most amperage as possible to bring the battery bank back up to as fully charged as possible in the time you run the engine.  Its a sailboat, you don't want to run the engine more than necessary.

So anyway, since the old alternator wasn't charging the way I wanted, I looked around for alternatives.  Balmar is the big name in marine alternators.  That's what I have now.  I didn't want to change the belts on my engine, and the maximum alternator for a 1/2" belt is 110amps.  I now have a Balmar 7-series 110 amp alternator.   There was a choice of a couple regulators they offered, I have the ARS-5.  The ARS-5 is a good quality regulator which supports 3 stage charging - although that appears to be true of all the Balmar regulators.

As I ripped out all the old wiring I realized the old alternator was installed with 10 gauge wire.  (A brief moment while people who understand the implications of this express a gasp of shock.)  (Sorry, more DC current nerd talk.)  While the wire runs where short, 10 gauge wire is small.  If the 80amp alternator was trying to charge at its limit, this would result in over a 3% drop over 2 feet.  It may partly explain why I never saw much output from the old alternator.

The new installation has 1 awg cable on the current side, which is pretty beefy.  I approached the problem that if in doubt, over specify.  I initially used the wiring harness that came as part of a package with the alternator (for $54) but ended up mounting the regulator in the lazarette to get it out of the heat and vibration of the engine.  So the wiring runs got longer.  After my initial tests extending the harness with 14 gauge wire I noticed a voltage drop across the wire from the alternator to regulator I wasn't happy with, so I ripped all the wiring out (again) and replaced it all with 12 gauge (for field, battery pos, neg and ignition.)  The wiring harness I bought ended up being shredded and thrown away, but the final result is sweet.  I initially installed a temperature sensor at the alternator, changed its mounting location once and later also installed a battery temperature sensor which was a little involved as the wiring run was a little round about as tends to happen on a sailboat.

I initially thought this might be a weekend project.  Maybe two.  It ended up taking longer, but I'm pretty happy with the results.  All the wires are nicely sized and run, I have new beefy alternator belts (Dayco Top Cog) along with a new tool to tighten the belt (go to MSC industrial supply, search for BJ10 - thanks to the Balmar support person who passed that along.)

Here's a picture.  It doesn't really tell the story.  But the real story isn't about installing alternators....its what I do with all this work in the end.


  1. Hey Craig!

    We have a Yanmar similiar to yours and had a Balmar 100 alternator. Keep a close eye on the tension in the mounting bolt at the foot of the alternator and at the bracket mounting bolt at the water pump. Our alternator ended up vibrating for some reason which broke the bolt off on the water pump, elongated the mounting hole for the alternator foot and ruined the alternator. Which is why Hello World has been tied to a dock for the last 6 months. We finally got it fixed last week but was a galactic pain in the ass.

    We think that part of the reason is that the Balmars have just a single mounting foot at the bottom, rather than the two feet that the Hitachi alternators have. Mainly, we just didn't keep a close enough eye on that part of the engine.

    Anyways, the install looks great! When are we gonna head out and anchor somewhere?


  2. Thanks for passing that experience along. There is a limit to the number of spares you can expect to carry along, and I wouldn't have thought that an alternator arm would be necessary! I'll be sure to add those items to what I look for when I check the engine.

    As for anchoring out wit ya all, that would be great! Luckness is going to be out of commission for most of the rest of the winter however. There's a lot of work going on. Spring time would be good!