[RE-wrenches] AGM set-points for 'opportunity charging'

Hugh hugh at scoraigwind.co.uk
Fri Apr 22 23:49:08 PDT 2011


At 14:19 -0700 21/4/11, Starlight Solar, Larry Crutcher wrote:
>
>I disagree about AGM life. I have heard others say this about AGM's 
>but it has not been our experience. I personally have a 900AH bank 
>that is 6 years old and shows little signs of aging. I have 
>equalized the batteries twice to keep the capacity up(each one 
>individually, constant current, unregulated voltage) We only sell 
>and install battery based systems at our retail store and about 50% 
>of sales are AGM batteries. We have found that they 
>have similar life to flooded batteries but with great benefits.

I am curious about AGM battery charging set-points.  I may be using 
Rolls AGM batteries for a telemetry application (unattended) with 
wind and PV inputs.  This will be 'opportunity charging'.    I wonder 
what set points I should use for absorption and float?  Is it safe to 
set absorption to 29 volts (temperature compensated)?  I may not be 
able to set it this high since the voltage will exceed 30 in cold 
weather and this may interfere with equipment.  But will the 
batteries like that voltage?  Float would be lower of course.  But in 
my experience the Tristar flits between the two settings in a 
slightly random fashion.

I am also puzzled by the above statement where Larry charges each 
battery string at constant current, unregulated voltage.  I wonder 
what current is suitable?

thanks
-- 
Hugh Piggott

Scoraig
http://www.scoraigwind.co.uk
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