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[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


Duane Siegfri
 

Dan,

Thanks for the informative reply.  

I had tried to upload a spreadsheet with our SG readings in it, but Yahoo was acting up.  I tried again in this reply, but it won't upload the attachment.  The average SG was 1.226 with a low cell of 1.215 and a high cell of 1.445.  

I think I'm probably going to have to remove the pair that has the low SG reading battery in it from the wiring.  I won't pull the batteries out of the box since they make for a nice tight fit.

The batteries were new in August of 2016, so they're less than two years old.  The next time I replace the batteries, I'm going to replace the charger as well.  Having a charger that will equalize the batteries, and has adjustable charging voltages, only makes sense.  The cost of the battery charger is about equal to new batteries so it's an investment, but we plan to keep the boat a few more years.

I'm still wondering when you replace the entire suite of batteries?  The lower limit of the "fair" range on my SG tester is 1.210 so I guess that's the trigger for replacement?

Replacing the charger with a charger/inverter, the inverter will be a boon for AC for the microwave and outlets (i.e. popcorn and computer charging anytime you want to!).  I don't expect my third Xantrex Prosine 1800 watt inverter to last any longer than the first two did (replaced sequentially under a two year warranty).

Thanks again,

Duane
Wanderer, SM#477


Dan Carlson
 

"End of life" of lead acid batts is a good question.  I would think that it is some relation to the banks ability meet your daily energy needs.  Perhaps getting thru the night and still being at a 50% state of charge in the am would be one value? Or some other value based on personal comfort (i.e.are you close to marinas and services or are you heading fare off shore...).    I think that with your solar capacity and generator, you can push your batteries close to that before replacing.  You can estimate state of charge in the morning before the sun gets up by the bank voltage. You can corroborate this periodically with SG measurements.

I monitor my batteries pretty much daily now by checking the bank voltage at 6:30am (before getting solar input), and noting the current load and my overnight consumption  (amp/hrs on the meter).  

I think another good question is battery bank capacity.  Our SM's were sizes up with 12 batteries when the extra freezer was added, and that was before solar. With significant solar charging throughout the day, do we really need 630 amp/hrs when you are using less than 10% overnight?  So based on this you can afford to remove a pair or two of bad batteries before you would need to replace the rest of your bank.

Sorry for the delayed response. We are off sailing.

Best regards, Dan and Lori Carlson on sv BeBe, SM#387. 








On Fri, Feb 2, 2018 at 1:39 PM, sailor63109@... [amelyachtowners]
wrote:
 

Dan,


Thanks for the informative reply.  

I had tried to upload a spreadsheet with our SG readings in it, but Yahoo was acting up.  I tried again in this reply, but it won't upload the attachment.  The average SG was 1.226 with a low cell of 1.215 and a high cell of 1.445.  

I think I'm probably going to have to remove the pair that has the low SG reading battery in it from the wiring.  I won't pull the batteries out of the box since they make for a nice tight fit.

The batteries were new in August of 2016, so they're less than two years old.  The next time I replace the batteries, I'm going to replace the charger as well.  Having a charger that will equalize the batteries, and has adjustable charging voltages, only makes sense.  The cost of the battery charger is about equal to new batteries so it's an investment, but we plan to keep the boat a few more years.

I'm still wondering when you replace the entire suite of batteries?  The lower limit of the "fair" range on my SG tester is 1.210 so I guess that's the trigger for replacement?

Replacing the charger with a charger/inverter, the inverter will be a boon for AC for the microwave and outlets (i.e. popcorn and computer charging anytime you want to!).  I don't expect my third Xantrex Prosine 1800 watt inverter to last any longer than the first two did (replaced sequentially under a two year warranty).

Thanks again,

Duane
Wanderer, SM#477