Battery life?

[Al Skierkiewicz]

Dale,
Nice charts. I would like to caution teams on a few things. Charging a battery while warm or hot will disrupt the charge cycle. Our batteries are better added to the charger after several minutes of cool down. While our batteries will regularly undergo several hundred amp loads, it is not wise to continuously draw high currents. As you point out, there is sufficient current drawn through the internal resistance. At 100 amps, the internal resistance is dissipating 110 watts at manufacturer's spec. This continuous high temperature can cause permanent damage. I believe that many of the early deaths we see in the AGM types are due to this mishandling. I have recommended the West Mountain Radio CBA II or CBA III battery analyzers for many years. While drawing currents in the 7-10 amp range, these analyzers will produce curves similar to yours, calculate AH ratings and allow curve overlays of the battery as tested over it's lifetime. The one volt drop in your curves is indicative of the surface charge being lost. This is one of the most confusing phenomena for teams who only measure their batteries, right off the charger, with a VOM. For those teams that wish to duplicate your method, a drop in 2 volts indicates a cell failure. Those batteries should be recycled or relegated to a 'practice only' status.