Technical info - Verlies van Actieve Massa

Shedding of active material

The active mass (paste) of the positive plate consists of lead sulphate. During charging this lead sulphate is converted into lead oxide, during discharge the lead oxide is converted back into lead sulphate.

Because lead sulphate has a larger molar volume than lead the active material will shrink and swell with each cycle, weakening and shedding the active material and ultimately leading to loss of plate capacity.

Accelerated loss of active material, also known as a PCL or Premature Capacity Loss can be caused by deep discharge. Typical examples of this are often found in applications where starting or semi-traction batteries suffer from an inadequate loading regime. Because with each charge the battery will receive less energy than it delivered, it will at some stage operate on a discharge level that it was not designed for and end it’s service life much sooner than expected.

Typical of pre-mature mass loss by deep discharge is that, other than in a normal wear process, the active mass is disintegrated, whereas the grid is unaffected.