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Old 18-07-2010, 13:41   #1
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Battery Charging Question

Here's the situation:

I have
  1. A Mastervolt IVO SMart 12/25-2 battery charger(12 volts 25 amps);
  2. Four new DEKA Pro Master GC15 6 volt 230 AHr, arranged to give me 12 volts and 460AHr; and,
  3. A Xantrex Link 1000 display.
The charger has been plugged in for a week and it is still in Bulk charge mode. It is putting in between 5 and 6 amps at 14.40 volts. [Note: Bulk is supposed to last for no more than 6 hours and stop when the voltage hits 14.25] Once, for a brief time after running the engines, I saw the voltage drop to 13.25 and the current drop to 1.0. This didn't last long though.

The batteries are not hot, nor are they emitting any water. They seem fine with this situation.

  1. Am I hurting my Batteries?
  2. Is my charger's little electronic brain scrambled?
  3. Is the charger just too undersized?
Thanks in advance from the Harbour View Marina in Marsh Harbour, Abaco, Bahamas.

"And all I ask is a merry yarn from a laughing fellow-rover
And quiet sleep and a sweet dream when the long trick's over."
John Masefield
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Old 18-07-2010, 14:23   #2
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Sounds to me like it's in absorbtion mode and given it's small size could stay there forever especially if there are constant dc loads that the charger is also supplying


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Old 18-07-2010, 14:33   #3
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13.25 is the resting voltage for the charger, a few amps output would be normal just to provide a trickle charge. If it is not staying there for long and popping back up to 13.8 or so I suspect you have an intermittent load on your batteries from something.

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Old 18-07-2010, 14:39   #4
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Do you have any 12v stuff running? Refrigerator/Freezer?

I have the Trojan T-105s that are real close to your Deka's. Trojan recommends charging at a rate of 10-13% of capacity. In your case, this would be a 50-60amp charger. I have a 50amp shorepower charger and a 90amp alternator, and neither has any problem charging the T-105s.
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Old 18-07-2010, 17:04   #5
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Sounds very much like you have a DC load on the batteries which the little charger is struggling to keep up with. Frig, maybe?

Yes, the charger is a bit undersized for the battery bank you have. A charger in the 50-75A range would be better. In your stead, I'd be tempted to pick up an Iota DLS-55/IQ4 or DLS-75/IQ4 to handle the battery charging task, keeping the Mastervolt in reserve for when you are dockside and don't have any DC loads of significance. These chargers are relatively inexpensive and do a terrific job....under $200. Check on eBay or on Arizona Wind and Sun's site (excellent supplier).

Are you hurting your batteries? Probably not in the short-term, but matching the charger to the house battery bank and characteristic DC load would be a good idea.


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