Re: [Amel Yacht Owners] Re: Batteries


Dan Carlson
 

Thanks for the link Bill,  I had not come across that document before.   Or if I did, I discounted it, as it was really focused on their industrial batteries.    I had found some more general specifications documents and guidelines.  

It sounds like I will need to do some checking of the specific gravity.   The document recommends that the battery stabilize for an hour to get the most accurate reading.  Is that your typical practice.     

In addition, I think that I will continue to periodically record the morning voltage and overnight amp/hr consumption as an easy indicator of any changes.  

Best Regards,  Dan & Lori Carlson, SM#387, sv BeBe


On Wednesday, December 13, 2017 9:48 PM, "greatketch@... [amelyachtowners]" wrote:


 
Dan,

For flooded cell batteries like yours the absolute "gold standard" for determining state of charge is to measure specific gravity of the electrolyte. This tells you a lot about the health of the batteries.  Everything else is a poor imitation of that.  It's a lot simpler than a discharge test, but a lot harder than reading a meter!

On my Victron MPPT controller I can set any parameter to any value.  If I was leaving the battery for a long period unloaded and was depending on the solar panels as my sole charging source, I would set the absorption voltage to be the same as the float voltage to hack the system to maintain a steady float voltage level.

On your system, 27.2 volts seems a trival high for float voltage (typically 27.0 for flooded cells at 25C) but very low for absorption voltage (which can be as high as 29.6V at 25C)

You might find this from Deka helpful.  I doubt they distribute it with every battery they sell... 

It is a bit a a slog through, but worth it!

Bill Kinney
Sm160, Harmonie
Fort Lauderdale, FL


---In amelyachtowners@..., wrote :

Hi Bill,  thanks for the response.  I appreciate  the information on the Victron  controller.  It is on my list to take a deeper dive into exactly how it works.  And perhaps when the boat minder came and measured the voltage each month (And took a photo) the 27.2 was reflecting the absorption level, not the subsequent float at a lower temperature adjusted level? 

The batteries are DEKA DC31DT "Marine Master" deep cycle lead acid, with "Low antimony, low maintenance grids."  You have to peel off the battery label to access the flush caps on the top, and there was not an obvious maintenance schedule innthe product information.  

I do understand that the xantrex measures current flow, but it also measures the voltage, which is another indicator of state of charge.  That is why I think tracking amp/hr usage overnight and the morning  voltage before the sun significantly kicks in might give me some reasonable objective data.  At the same time, I recognise that the morning voltage the xantrex shows is from the battery under a load, so it cannot be direct reflection of state of charge.  As for individual battery performance, that seems to require measuring each battery separately with a battery tester, which I only do every couple of months.  

I will also look into the desulphating process as well.

Going back to the MPPT behavior: my first thought would be to see if the controller could be set to only the float level?   If tjat is not possible, then perhaps leaving something that would only use enough current over night to allow the batteries to absorb that initial morning bulk/absorption period befire the battery then goes to float.

Thanks and regards, Dan and Lori Carlson, SM#387, sv BeBe

 


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