1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Battery Life Cycle

  1. Dec 11, 2012 #1
    Hello,

    I have seen graphs of Battery's DoD (depth of discharge) vs Life Cycles. But at the same time, "life cycle" is defined as the no. of COMPLETE charge-discharge cycles that a battery can perform before its nominal capacity falls below 80% of its initial rated capacity.

    Here's the contradiction:
    From the definition, the term "life cycle" should only be valid for a DoD of 100% (or maybe 80%, whatever is the max. possible value). How can the battery's life be rated in terms of life cycle? In those graphs, does "life cycle" simply mean discharging to a specified amount (DoD) and then charging rather than COMPLETELY dscharging and charging the battery?
     
  2. jcsd
  3. Dec 14, 2012 #2
    Yes, you discerned it correctly, the graph measures the life of a battery [defined as having worn to the point of 50% of nameplate capacity] vs the DoD [Depth of Discharge]

    However, out in the real world, with scooter and power wheelchair batteries I see lifes much shorter than I would expect based on these graphs.

    I see commonly AGM batteries lasting 2-3 years. At one cycle per day, that is ~600-900 cycles. At a mere 10% DoD AGM batteries are expect to last {ON Average} over 2000 and Gel batters over 6000 over 10 years! This does not happen out in the real installations.

    Open Questions to me:

    1. Why not? Is it something to do with the moving / shaking causing the premature battery failures. Is perhaps the quality / size of charger? Maybe the load current is higher in the scooters? Do not know.

    2. The graphs of DoD all start at approximately 10% what happens at 5%?
     
  4. Dec 17, 2012 #3
    There's an interesting article here that might illuminate what's going on. Apparently, lead-acid batteries, regardless of the type, have a fairly narrow charge-discharge window, and going outside it stresses them. That's why car makers are so interested in Li-ion, which has its own set of problems, of course.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Battery Life Cycle
  1. Einstein cycle (Replies: 12)

  2. Diesel cycle (Replies: 1)

Loading...