Regards Power saving

[sivasuren]

Hello friends,

          I just running a device in 35AH battery with 12V. after 2 or 3 days my battery voltage level becomes to 11.5V. In this stage how can i calculate remaining amph's in that battery. 

         May be my question will be irrelevant. But i am trying to understand when voltage start to reduce. is it depend upon amph's? or any other thing?

Best Regards,

SivaSuren 

[_Bryan]

I am no battery expert, but I can help some.

I am going to assume you are using a lead acid battery since you did not specify what type you are using.  Different types of batteries will discharge differently.  At 11.5 Vdc you have about 10% of the capacity left in the battery and it is probably going to start getting damaged soon.  Looking around the internet you generally do not want to take a normal battery  to less than 20% of charge (11.66V).  You can find charts for 12V battery voltage vs state of charge charts using google.

I you want your battery to last a specified amount of time you need to find out how much power you are using and how long you want the battery to last.  Here is a site that will give you more information about lead acid batteries.

http://all-about-lead-acid-batteries.capnfatz.com/all-about-lead-acid-batteries/lead-acid-battery-fu...

You can look up the differences in output between lead acid and lithium ion.  Lithium Ion batteries hold a more constant voltage and then drop off.