Lead Acid Battery Interrupted Charge Control  Algorithm

This algorithm (ICC) is reviewed in [1] and described in more detail in [2] where it is applied to a small AGM VRLA battery.
  1. The bulk phase charging operates as above, although the authors of [2] use a charge rate of C/10 which is quite low. This delivers over 95% of the charge to the battery.
  2. The battery stands idle until the terminal voltage reaches a low limit equivalent to 97% of the capacity.
  3. A pulsed charging mode is used at C/20 with current on for 10 seconds and off for 20 seconds to allow the battery to cool. The charge time is too short for the battery terminal voltage to reach the gassing voltage until a number of cycles have been completed.
  4. Pulsed charging continues until the terminal voltage again reaches the gassing limit.
This is claimed (without any explanation) to be designed to leave the battery fully charged with minimal thermal stress and overcharge, thus resulting in much longer battery life. It can also assist in equalization in component cells in a battery string. Some experimental results are provided to support this claim. It is noted paradoxically in [1] that the battery tends to be left slightly undercharged. Note the long charge times and inefficient use of the charger as reported in [2]. Thus it is best applied to off-line chargers. The authors present experimental results showing the pulse charging time to be about twice that of the bulk charging time, with an overall charging time of over three hours from a depth of discharge of 15%. This is not seen as a disadvantage for the application under consideration (standby systems).

The duty cycle of the ICC algorithm needs to be adapted as ambient temperature rises. The voltage limits are also adapted according to the manufacturers' datasheets, however the duty cycle adaptation requires understanding of the thermal processes in the charging battery. As the battery ages the oxygen recombination reaction tends to dominate the activity at the negative plate and will require further adaptation of the algorithm.

Oxygen generation and recombination will become significant when the battery reaches its gassing voltage. The ICC method of charging removes the charger at that point and drops the battery to a lower charging current. Once the battery is fully charged all the current will go into oxygen generation and recombination and this claimed to occur only at the very end in the cycle of pulsed currents.

References

  1. "Charge regimes for valve-regulated lead-acid batteries: Performance overview inclusive of temperature compensation." Y.S. Wong, W.G. Hurley, W.H. Wölfle. Journal of Power Sources 183 (2008) 783–791.
  2. "A New Approach to Intermittent Charging of Valve-Regulated Lead–Acid Batteries in Standby Applications", M. Bhatt, W.G. Hurley, W.H. Wölfle, IEEE Trans. Ind. Electron. 52 (2005) 1337–1342.
  3. “Mathematical modeling of current-interrupt and pulse operation of valve-regulated lead acid cells,” V. Srinivasan, G. Q. Wang, and C. Y. Wang, J. Electrochem. Soc. 150, A316–A325, 2003.


First created
13 October 2014
Last Modified 13 October 2014
© Ken Sarkies 2014