Re: [Amel Yacht Owners] Wet Cell Batteries

Dan Carlson
 

Hi Duane,  I also have the DEKA group 31 Marine Master batteries (DC31DT) , installed December 2016. I am not an expert, but can only relate my specific experience.

After 6 mos on the hard in Trinidad this summer I was down to 1mm of electrolyte over the cells. It took over 3 gallons to get the 12 batteries back to the mark.  Initially, 5 of the batteries tested "bad" with very low CCA results and overnight the voltage would drop to 24.6- 24.7 volts with only about 45 amp hrs consumed.  

But over time, with "excercise" they have regained some performance.  They charge well, and now test over 650CCA per battery, and the fully charged electrolyte SG ranged from 1.240 to 1.260, with most at 1.250.  And the drop in the SG in the over night is about 0.010.  Last night we used 55 amp/hrs overnight and the voltage was 24.9 at 6:30am. I am trying to see if I can recover a bit more performance.  

I have 405 watts of solar. The MPPT is set to 28.2 absorb and 27.2 float.  I think 27.6 might be a bit high.  When I left to boat on the hard with no load it would still start each day with 28.2 for an hour, that was not good. And by my calculations, even the 27.2v float was to high for the hot on shore temperatures.

DEKA does have a pretty good manual for care for their industrial batteries, and they also answer their technical support phone +1 610 682 4231.
Here are some of the specs that they gave me:
  - bulk/absorb - up to 29.2v 
  - float - 13.5v 
  - equalization - 31.5v until voltage stabilizes 

I also have the Dolphin chargers without equalization capability.  For me, it seemed that discharging the bank down to about 80 - 85% of the theoretical capacity and then fully recharging with the 100amp charger gave me noticeable improvement in overnight voltage drop.

Perhaps that helps.

Regards, Dan Carlson on sv BeBe,  SM#387





On Tue, Jan 30, 2018 at 10:40 PM, sailor63109@... [amelyachtowners]
wrote:
 

I'm trying to understand the condition of our house battery bank.  I'm definitely not a battery expert.  We have the original Dolphin Battery Chargers (100A and 30A).  We use the 30A at the dock and the 100A with the generator.  We also have a Victron Blue Solar 100/30 with 630 watts of solar panels.  The installer set it at 28.8V Absorption and 27.6V Float (Position 2).


First:  The 12 Group 31 house batteries use about 0.5 gallons/month...is that excessive?  I'm wondering if the MPPT controller is overcharging the batteries.


Second:  How close to replacement are we?

I checked the specific gravity of all cells recently (see the attached spreadsheet).  I read that a new, fully charged cell should be at 1.265, and is discharged at a SG of 1.120.  The best cell tested at 1.265 and the weakest cell at 1.145 (corrected for temperature).  The average SG of all cells was 1.226.  This SG corresponds to 75% state of charge from what I read.  At SG of 1.190 the battery is at 50% SOC and battery #3 has three cells in that range.


Third:  Should I just replace Battery #3?


Fourth:  I've read that when the difference between cells in a battery is greater than 0.03,0 the batteries would benefit from equalization.  My Dolphin chargers are not adjustable (at least as far as I can tell).  The MPPT has an equalization function that will run for an hour.  Will that be sufficient?


Thanks for your input,

Duane 

Wanderer, SM#477

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