ASTM D7129-05

Nickel metal hydride (Ni-MH) cells can exhibit high self-discharge rates. Nitrate impurities in the positive electrode can be reduced to ammonia on the negative electrode. This causes rapid self-discharge. Technical publications have reported a link between the separator ammonia trapping capabilities and the cells charge retention. Grafted polyolefin separators can absorb or trap these impurities—hence, reducing self-discharge rates. The level of ammonia trapping from this method gives an indication of the efficiency of a separator to trap these contaminates, thus helping a battery self discharge ( charge retention). A higher value should provide a cell with greater charge retention.

1.1 This test method covers the measurement of the ability of a material to capture ammonia.

1.2 This test method is intended primarily for testing grafted polyolefin materials used as a battery separator, although other materials could be tested.

1.3 The values stated in SI units are to be regarded as the standard.

This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.