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As I understand it (and I had this on my last boat) a big alternator with an external 3 stage regulator will bulk charge the battery bank at its current acceptance rate until the voltage reaches the absorption voltage - in our case approx. 28.4. The reg then backs off the field current to the alternator to maintain the absorption voltage (inclusive of any devices drawing current from the system) for a predetermined time or until the current from the alternator drops to a predetermined level (eg less than 10% of Ah capacity), and then switches to float.
The temperature compensated systems measure the battery temperature and modify the charging profile accordingly...cold batteries need a higher voltage than warm ones
The problem with internally regulated alternators is that they don't bulk charge, absorb then float. They just sit at the set voltage forever and never float.
That seems to me to be a problem if you motor for a long time.
If anyone has knowledge / experience of rewiring a neg regulated Leec-Neville alternator for an external reg., I'd appreciate hearing from you.
--- In email@example.com, Richard03801 <richard03801@...> wrote:
Please take note 28.4 bolts is not over charging a large 24 volt system. Second when the new smart chargers see max voltage they move to float. Second as you are motoring you are also using a rather amp hungry group if this and that on board so the alternator also needs to keep up with those. Third a smart charger will normally and a heat sensor that tells the smart charger when the bank is to hot. When it sees over heating it goes to float.
In any case the sooner you go with a modern smart charger that is equal in output to at least 10% of the AMP hours of the bank the better.
Cell 603 767 5330
On May 23, 2013, at 19:37, "alan_leslie_elyes_sm2k" <divanz620@...> wrote:
Another thing that could cause this is extended motoring.
The 170Amp alternator on our engine is internally regulated to 28.4 volts. So it outputs whatever current it can at 28.4 volts all the time. If you motor for long periods of time this will overcharge the batteries...and could lead to boiling off the electrolyte.
I'm looking at changing this system to have an externally 3 stage regulator that will bulk, absorb and then float. I don't think this internal reg is good for deep cycle batteries.
I contacted Leece-Neville about this and it is not so simple to change as my alt. is regulated on the negative side so its not just a matter of taking out the internal reg and connecting the brushes to the field excitation from the external reg. There's some serious rewiring involved.
I would be interested to hear from anyone who has done this ...
Alan & Judith
--- In firstname.lastname@example.org, "rxc" <rxc@> wrote:
It was on a boat that was not an Amel. (I am a Jeanneau owner, but follow this list because you have some interesting topics) The Freedom inverter/charger had a sensing line wired directly to the batteries. I have also seen alternator controllers wired like this. It is done to make sure that the voltage that is being sensed is the actual voltage at the battery terminal, and not at the output of the charger. If there are significant losses in the transmission cable from the charger to the battery, the charger could sense an eroneous voltage. Also, if the sensing line has a bad connection it will see the same condition. Connections should be one of the first thing checked when you have a problem like this. Alternatively, use a voltmeter to check the voltage at the charger output and compare that to the voltage at the battery.
When it happened on my boat, my wife was living on board, and the on-board smoke detector kept going off, but there was no sign of smoke or fire in the boat. Turned out that as they overheated, the batteries gave off fumes that set off the smoke detector. If we had waiting longer, the batteries would have gotten so hot they might have started a real fire. It was a close thing.
--- In email@example.com, Kent Robertson <karkauai@> wrote:
Hmmm. That's very interesting, rxc. The only connection to the batteries with any of my chargers is the output line of the charger...Is that what you are referring to?
From: rxc <rxc@>
Sent: Thursday, May 23, 2013 10:44 AM
Subject: [Amel] Re: Battery bank problems SM with 13 batteries
One very important thing to check is the condition of the voltage sensing line from your batteries back to the charging source, whether it is the alternator or a shore charger. I once had a Freedom charger cook some very nice trojan batteries because the fuse-holder in the sensing line developed a bad connection, and the charger thought that the voltage was lower than it was actually putting out. Very high voltage and boiled batteries. Bad connections can cause this.
--- In firstname.lastname@example.org, Richard Piller <richard03801@> wrote:
If you speak with any battery expert they will tell you that the battery charger must be no less than 10% of the amp hours of the bank you wish to charge.
AMEL. Never intended the 30 amp charger to be anything more then a trickle charger at the dock when the batteries are topped off the start with. If you try to top off discharged batteries with the 30 amp charger what has occurred with a rather large number of Amel owners is the charger overheats cooks its internal regulator and never shuts off the result being cook battery bank.
In today's world of smart chargers buy one 120 amp charger and can the 30 .
Sent from my iPad
Capt Richard Piller
On May 22, 2013, at 16:18, "eric" <kimberlite@> wrote:
On our trip home from St Martin last week, we discovered that most of the liquid in all the sealed maintenance free batteries had boiled off. I did not realize that under the labels there are plugs where water can be added. In any event all the house (12) batteries
have to be replaced.
We have a 175 amp alternator and 30 and 100 amp Dolphin chargers.
I spoke with Dolphin and they said that the 30 amp charger is too small for the bank and it probably cooked the batteries as it saw the bank as always needing a charge. I plan on having the alternator checked and then speak again with Dolphin when I install the new batteries.
Kimberlite usually is in a marina somewhere and plugged in with the 30 amp charger running.
Any thoughts on my problem?
Amel Super Maramu #376 Kimberlite
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