Re: 175 amp alternator on SM-burned up battery bank.

Alan Leslie

Hi Trevor,

At 28.1-28.6V you are probably OK...its when it stays at 28.8V for days that I think there is a problem re gassing the batteries and ultimately battery failure
But WHY your alt puts out 28.1-28.6V is a bit of a mystery when the standard internal reg is set for 28.8

The Dolphin chargers re SMART chargers, I don't know why the 30 and 100 A docs would be different...its really a case of whether or not the charger can keep up with the load imposed on it.

As to why Amel didn't buy an externally regulated alt to put in the only thought is that they didn't understand well how batteries need to be charged

BUT, having said that, the system we have is perfectly OK..UNLESS we motor for long I did..54 hours last week.

I don't agree that it's a "black art"..I think that there is a lot of "bad" information out there.

I have more than 15 years experience with different alternators, chargers, batteries, in different boats and I think I understand the best way to do it...and that is DEFINITELY NOT to have a 28.8V internal reg in the alternator !

Hence I am trying to find a way to externally reg this 175A beast that we have, properly !


--- In amelyachtowners@..., "seafeverofcuan" <seafeverofcuan@...> wrote:

Hi Eric,
I was hoping that you would post your findings re. you alternator. We are now at the bottom of The Sea of Cortez and hope to get some good technical help in Mazatlan next week. For now we are running on four remaining house batteries. The alternator has been putting out between 28.1 volts to 28.6 volts the remaining batteries have not overheated.
I have the original Dolphin instruction paperwork from 2004. The 30amp charger should boost at 27.7 volts and float at 26.5, the 100amp boost 28.8 and float at 27.2.
However both pieces of paper ( and that is literally what came with the boat) state

"The charger system will revert to boost when the battery system requirements equal 50% of the charger rated output"

My reading of this is that in our case with twelve house batteries giving 630 amps at 24 volts then the 30 amp reverts to boost when the batteries drop below 97% of total capacity.

My 30amp charger now only produces 27.3 volts, I have asked Reya for advice and haven't had a reply as yet.
I suspect the answer lies in a total replacement of both chargers with a smart charger and of course a new set of batteries. From everything that I have been reading, common sense would indicate AGM and completely disconnect them when leaving the boat for long periods.
The entire subject is a black art and I suspect in my case choices will be heavily influenced by what is available in Mexico.
Best regards,
Sea Fever

--- In amelyachtowners@..., Sailorman <kimberlite@> wrote:

I had my alternator checked at a very excellent alternator shop and the
owner showed me what happens as it runs. There is no internal regulation.
However he said as the battery becomes more charged the resistance of the
bank increases and the alternator puts out less and less amps . It has a
constant output of about 28.5 volts. He said the Balmar smart regulator is a
waste of money -and he sells them.

I had no problems with this alternator with my first set of batteries for 4
years. I only changed the batteries after a lightning strike.

My current burned out battery bank must have been caused by the charger. I
will test it when I get my new batteries next week.

Fair Winds


Amel Super Maramu #376 Kimberlite


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