I am confused by your response, after rereading Nigel's article and your "Musing Regarding External Regulation" my understanding of the ProAlt-C is that it as a DC-DC converter independently adjusts the voltage to the battery independent of the alternator voltage, which over comes the deficiency of the "super dumb" alternators which "can drop to 13.4 volts when hot" and therefore allows correct Bulk charging to occur, followed by correct Absorption charging. The ProAlt-C does not control the alternator at all, but accepts whatever voltage it puts out and generates the proper battery voltage independently. Additionally it can do this simultaneously on a starting battery.
In order to derive the max output from the stock alternator the PAC has to pull the voltage of the alt down, below its limiting voltage, to approx 13.3V-13.4V, thus forcing the factory alternator into bulk charging or its maximum output. So yes the PAC does control the alternator by pulling the voltage down and tricking it into full output.
The PAC can absolutely do this but the factory alt will get quite hot during bulk charging. When the alt gets hot PAC's temp sensor then signals the PAC to stop boosting. This occurs at approx 200F - 212F. When the alt cools off it resumes the boosting until it heats up again and repeats.... In the real word, during bulk and early absorption, it's very often a
boost>off>boost>off >boost>off scenario, especially with the small stock alts typical on older boats.
Once the bank finally gets to absorption voltage the alt will then catch a break and the PAC can really do its job and not have to do the boost>off>boost>off to protect the alt.. On many boats, when charging from 50% SOC, bulk can be well in excess of an hour, even at a .2C charge rate or 20% of Ah capacity. With a small factory alt and a charge rate of closer to .1C (10% of Ah capacity) the bulk duration is even longer.
In my experience the PAC works better on newer 100A and larger stock alts (Yanmar, Beta etc.) but can still cause them to get hot enough to shut off boost mode. Yes, the PAC
can boost the voltage to the battery, and this will certainly be better than the stock regulator, especially when it gets to absorption. That is
if you're running the engine long enough to attain absorption voltage. The performance, due to the manner in which it operates its temp sensing circuit, is less efficient than an external regulator that uses
adaptive temp sensing and finds the absolute peak continuous output the alternator can safely run at.
My second confusion arose with your critique of the ProAlt-C's float behavior when you previously said "Is Float Necessary On Sailboats? In my opinion, mostly no." In any case why would the ProAlt-C stop functioning as a dc-dc converter regulating the battery voltage during float? Wouldn't it continue as long as the alternator voltage minus a diode drop was less than the desired battery voltage?
The PAC is not a buck/boost device, like the Sterling Battery to Battery chargers, which were also referenced in that article, and the Sterling B2B's are tremendous devices. The PAC is a
boost device.. There are alternators out there running 14.6V to 14.8V, many Delco's, or even 15.1V voltage set points such as found on a number of Motorola/Prestolite/Leece-Neville alternators so in those cases, on long motor runs, a float would be welcome. When the PAC goes to float mode it is essentially just operating at alt voltage minus the diodes drop. In float there will be minimal current flowing into the battery and the alt will cool off so the regulated alt voltage will be near the factory set point. On most Hitachi's this works out to be about 13.8V - 14.1V, which is going to be fine for the amount you'd actually run the motor.
"When the batteries have been fully charged, the voltage is reduced to float voltage (appr. 13.5V to 13.8V)
if possible,
depending on the output voltage of the alternator."
In
most cases alt float is
not necessary on many sailboats. Unfortunately far too many external regulators are set up
incorrectly so as to enter float prematurely. So yes, that is still a float = "
mostly no". There are situations however where a trawler owner or sailor is traveling long distances under power and a true float would be nice.
The PAC is not going to "
over charge" house batteries on a sailboat but I can't with a good conscience not accurately inform my customers about how it actually works vs. the way it is often
pitched or
appears to the end user. If you read the sentence above carefully you see that Charles is very careful to state that 13.5V to a 13.8V float is only possible
if the output voltage of the alternator allows for that. A big deal? Not really, but it should be mentioned because some boaters are expecting a true float like a shore charger, external regulator, solar controller or one of Sterling buck/boost battery to battery chargers especially a customer that does long motor hours and may have expensive AGM batteries such as Firefly's.
At $280 (Defender) and requiring no modification of an alternator, it seems a cost effective improvement for standard alternator systems. Increasing alternator capacity only speeds up the charging process. I suggest anyone interested, read Nigel Calder's article in Sail magazine. It is bang for bucks trade off.
$280.00 is a
steal for a Pro Alt C and I have to assume Defender got a special deal on a large purchase for the sale. The Balmar ARS-5 is also on sale at $280.00, another tremendous price, and this would yield even better performance due to the small incremental adjustments it makes to find max continuous output vs. boost>off>boost>off...
Tapping into the alternator brushes is easy, so I always educate my customers, when they ask, as to the differences between an A2B and a true external regulator such as the Balmar. When I can give them better performance on the same alternator, from an external regulator they usually jump at that idea.
I have played with and tested the PAC's quite extensively and it's the factory alts that can't keep up with the PAC not that the PAC can't do the job. The PAC is simply limited by the alternator being pushed too hard and over heating and requiring temp protection.
The Pro Alt C is not a bad device it's just not going to yield the
same performance as an external
adaptive temp sensing regulator due to the way it operates its alternator protective temp sensing circuitry and the ping-ponging that goes on when the alt gets hot. The PAC is a more of a convenience device for those not inclined to dig into the factory alternator to access the brush wires but it's really not a big deal at all.
The Sterling is easy to install and will certainly yield better performance than the stock alt but not what a true external regulator conversion will do.
