Alternator and Solar

[ralay]

Resurrecting this post to commiserate with how hard it is to troubleshoot alternator/battery problems.  We had "alternator" problems towards the end of our trip this year and it took me forever to figure out that the problem was a combination of mismatched belts and our batteries. 

We had two symptoms of trouble.  The voltage of the alternator started to drop from the regulated voltage to ~13V.  The voltage problem varied with RPM and could sometimes be fixed by tightening the belt.  The second problem was that the alternator output had dropped even when belt was tight and was at the regulated voltage.  We couldn't get more than a few amps to trickle into the batteries even when they ought to be sucking it up.  One day when the output and the voltage dropped to zilch, I took off our alternator for testing.  Both a chain store and a dedicated alternator/starter shop told me it was totally dead and wasn't putting out anything.  I put on our spare alternator, but it soon had exactly the same issues.

To make a very long, frustrating story short, I'm pretty sure we've tracked it down to a combination of mismatched belts (Japanese 11mm belts and American 3/8" belts are not quite the same in width or bevel angle) and high internal resistance in the batteries.  Once I put a fresh, tight belt on the "dead" alternator, it shot right back up to its regulated voltage.  Not sure what those folks do in the back room when they're "bench testing."  What I thought was the alternator's reduced ability to put out, is, I believe the batteries' reduced ability to accept.  When I remove them and hook them up to a 3 stage 110V charger, they fool the charger as well, which quickly switches to "float" even though the batteries aren't fully charged.  For me, it was incredibly hard to figure this out as our boat has such tiny loads.  The solar panel was floating many of our loads during the day and at night we were falling asleep before our little LED reading light could even bleed the surface charge off the batteries.  So I thought, incorrectly, that they were holding a charge.  I finally had to pull the solar panel fuse, turn every light on the boat on and leave it on for 20 minutes before I could see the battery voltage drop precipitously.  Only then did I realize that the batteries had severely reduced capacity and our charging problems were likely due to high internal resistance in the batteries.  So 4 new (ouch) batteries are in our future, though I don't plan to replace them until we're ready to start moving again.  Might as well squeeze out as many cycles as we can while we don't need to start the engine.   

I just wanted to share this as another example of how enraging and hard to pin down charging system problems can be.  Also, if I had trusted the folks at the alternator shop, I might have blown money on a new alternator while failing to fix either actual problem.  As it was, we had an old spare, so I bought myself some time to figure it out.  If anyone needs more encouragement to be skeptical of the information you receive from pros, I'll give it to you.  I am a little disappointed I don't have an excuse to open either alternator up after doing so much reading on rebuilds, but I'm sure they'll break for real someday soon.   ;)

[Bob J (ex-misfits)]

Putting the alternator issue aside, any chance that the batteries are sulfated due to not being properly charged & therefore are no longer to accept/hold a charge? I'm no expert but anything I've seen out there on battery problems usually stems from not knowing what the actual state of charge is? Batteries can show 13.5 voltage but may not be topped off.

[ralay]

Yes, I agree.  The batteries are probably sulfated and have reduced capacity and no longer can accept/hold a full charge.  The high internal resistance is reducing the flow from the alternator and battery charger to a trickle.  The batteries came with the boat, which we've had 3 years now.  The boat was for sale for 1+ years, so the batteries are a minimum of 5 years old.  They're probably nearing the end of their useful life.  They're only designed to put out so many cycles, and there's a lot of cycling going on when you live on your boat 365 days a year.  Makes me cry a little to add up the cost of 4 new ones, but that's what we get for letting our electrical system get complicated.  :'(

[Cyric30]

Ralay
Do you know who made the batteries and what there Ah are? i dont know the your specifics, but a battery bank should be doing better than that ?

[ralay]

They are Odyssey 65Ah batteries.  I have a lot of manufacturer data from their website.  From their data, they expect the batteries to perform well for about 410 cycles before starting to decline.  In their opinion, an 80% loss of capacity marks end of life.  I'm away from my Nigel Calder books at the moment, but I remember that being roughly normal for deep cycle batteries.  As I said, if you have a boat that sits at the dock most of the time, it might take you a decade to get to 410 cycles.  In the last 5 or 6 years years, our boat has gone from the Pacific NW to Panama to Fort Lauderdale, FL.  Then to TX and back.  Then up to the Chesapeake, and back down to NC.  That's a lot of use.  The batteries also don't have a date marked on them.  So I'm saying they have to be a minimum of 5 years old and that would be assuming that the owner bought 4 new batteries for a boat he was putting up for sale, which seems unlikely. 

[CharlieJ]

You guys over for S X SW? Or will be soon?

[Bob J (ex-misfits)]

They are Odyssey 65Ah batteries. 

That's a pretty small bank for a boat being used full time.

[Norman]

Ralay if you keep an AC charger on continuously for an extended time, it will burn through some of the sulfation.  Most people are not patient enough to get much from that, but if you are in a marina, charge 27/7 and you may see an improvement.  Engine charging will not be continuous enough to get any results.  I have done this with batteries from my cars, too weak for reliable service, charge for a month, and test much better. Instal in the boat, fine for the amount of load I have.

Does your charger have an "equalize" setting?  That is the one to use.  Check water level, as some will be lost.