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Battery amp hour rating vs use

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Posted by ...........Rob on October 21, 2015, 3:57 pm
  I'm a little confused with my battery's amps.  I have a solar lighting sy
stem connected for the front lights (driveway)and the rear stairs (for the  
dogs).  Now with winter approaching I decided to set my C12 controller to r
un dusk to dawn.  According to an analog ammeter connected in line the syst
em draws 2 amps (double checked with a clamp on ammeter).  

  I have 4 t105's connected to give me 440 amps @ 12 volts, they are 1 year
 old.  2 days ago checked SG (all were good and close to each other), and w
atered. I have only once drawn them down (exercise?).  

  Now my confusion.  They started out from float yesterday.  This AM the vo
ltage was down to 12.3 volts.  Counting 14 hrs on time I drew 28 amp hours  
from the battery's. In theory I should be able to run this for 2 weeks or s
o (wouldn't, but if I wanted to run them empty).  12.3 is close to 50% of t
he battery lets say 200 amps?  

  Is there something basic I am missing? From reading here over the years I
 know voltage is a poor way of determining SOC, but voltage seems low to a  




Posted by adsDUMP on October 21, 2015, 5:29 pm
On Wed, 21 Oct 2015 08:57:56 -0700 (PDT), "...........Rob"

The amp hour rating may be to discharge: 10.8 volts.  Do you have the
specs for that battery?

What voltage are you charging the battery to?
That depends on the type service - standby versus cyclic.  I'd guess
your usage is cyclic and the charge should probably be something over
14 volts.  Again, do you have a spec sheet for that specific battery?

Posted by Vaughn Simon on October 22, 2015, 2:21 am
 I have a system that must be very similar to yours, except that I  
currently have only one string of 2 T105 batteries.  My morning voltages  
are very close to what you are seeing.  I also found that mildly  
disappointing, so I simply stopped paying attention to it since the  
system does everything I need it to do.

I have three 12 volt yard lights on the system (C12 set for 4 hours),  
and a few lights inside the house.

Posted by ...........Rob on October 22, 2015, 4:16 pm
 On Wednesday, October 21, 2015 at 9:22:13 PM UTC-4, Vaughn Simon wrote:

  Thank you for your reply.  Mine also works a required, so I'll take your advice. Another one of life's mystery's.

Posted by Jim Wilkins on October 22, 2015, 7:03 pm

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