Tartan37.com

I have a Balmar 80 amp alternator, the ARS 5 regulator and the Xantrax LinkLite. Installed all of them several years ago and have had no problems. As of late, however, the alternator output seems much lower. Instead of getting maybe 50 amps output in the bulk phase, I might get 15, and then that drops off to 10 or 12. And this is after the batteries have been run down a fair amount.
Checked the belt and it is nice and tight, as are all electrical connections. One thing I have noticed is that the "BV" reading on the regulator might say 14.0 or 14.1, while at the batteries the reading is more like 12.9 or 13.0. I thought the "BV" reading on the regulator should be the actual battery voltage? Suggestions? Alternator problem? Regulator? Thanks.

When troubleshooting, break things into halfs. The quickest way is look at your voltage regulator owners manual in the trouble shooting section. You want to test the alternator by doing the magnetic test and flashing the field of the alternate. Refer back of the attached manual. Most of the time the ARS-5 either works or it doesn't. I have rebuilt my alternator twice in 23 years, both times do to low output.

http://www.balmar.net/wp-content/upload ... RS-5-H.pdf

There is nothing wrong with your system. I have a system very similar to yours and went through this. Battery monitoring systems now tell us what is going on and you are wondering about the same things that perplexed me.
This is the problem of having a large battery bank that you only partially discharge, a "smart" regulator, and a large alternator. One of the problems with the marine marketers is that they make all of us believe that more is better in size and sophistication. Your situation is a great example of how this works out in the real world.
The key here is your "smart" regulator doing its job. Smart regulators sense the feedback from your battery bank's voltage and taper the charge. As your bank gets closer to fully charged, it has a higher ambient voltage feedback to the regulator--and the regulator tapers the voltage it is allowing to go from your alternator to the bank. So, unless you discharge your bank down to 50% or so of battery capacity (and its associated lower feedback voltage) you are not going to be able to deliver high voltage or high amperage to your batteries. As the charging cycle progresses, even if you are discharged, the "smart" regulators are going to drag out the time--a lot--to fully charge your batteries because they taper the voltage as the battery ambient voltage feedback increases. In this sense, for most folks, buying a large alternator, a smart regulator, and a huge battery bank is a waste of money and vastly increases recharging time if you do not regularly motor for long periods of time and if you do not discharge your batteries regularly to less than 60% of their capacity. The key word here is "acceptance rate" of your battery bank which is interplay between the bank's voltage and your "smart" regulator's algorithm.
The magazines and the marketers will never tell you this, of course because they want to sell more stuff with more sophistication and size. By the way, some of these "smart" regulators have temp sensors on your alternator to cut back output which will further limit the output of your alternator---and many (if not most) engine compartments get hot enough to trigger this wonderful feature that will further limit the ability of your system to deliver meaningful charge voltage.
All these capabilities would be really nice if we were all world cruisers spending weeks out on the hook where we discharged our battery banks a lot or if we motored long distances---they would charge batteries more humanely than the old internal regulators. But the sad truth for folks who sail on weekends or just a week at a time is that "smart" regulators just make you go around all season with partially charged banks and incredibly slow charge cycles. Fortunately, most folks have shore chargers or use solar cells to offset this problem somewhat--they will top off your undercharged batteries. I hope you are not as depressed to learn this as I was after a year or two of consulting various industry experts and installers. As one expert said, "filling a big battery bank with the powerful systems most folks have these days, is like trying to fill a wine bottle with a sponge in it with a garden hose." The analogy sort of works if you think about it.

Ray Durkee
T37 #373

Thanks to both Puffcard and Velera for the suggestions. It took a while but finally figured out the problem. What puzzled me was not just that I wasn't getting the output for the alternator that I might expect, but the voltage readings seemed odd. The ARS-5 regulator scrolls through a number of different displays when the alternator is charging. And the difference between the "bv" voltage display (which should match the voltage at the batteries) and the actual voltage at the batteries was significant. I wondered if the reading given by the regulator was faulty, but when I put my own voltmeter on the terminals at the the regulator I got the same result. Tested everything else about the regulator as per the manual all of it seemed fine.
Technician at Balmar first suggested that I move the regulator's red sensing wire , which was connected to the alternator's positive battery outlet, directly to the house battery side of the main battery switch. But that didn't help. He made a couple of other suggestions, none of which seemed to work. And finally he said that I should try a much heavier ground wire from the alternator to the main negative bus bar. And that was it. I now have a #2 gauge cable coming off the alternator ground with a short 2 foot run to ground. And with the batteries down maybe 50 amp hours I get better than 60 amps output during the bulk charging. The mistake I'd made was not beefing that ground wire up when I went from the old Zenith alternator to the larger Balmar.