This analysis is based on the 38 Iridium APEX floats deployed by CSIO in the period of 2010-2016. We choose 35 inactive floats, of which 22 floats were installed Lithium and Alkaline battery packs and, the other 13 were only installed Alkaline packs. It is found that the lifetime of the floats installed only Alkaline packs is about 100 cycles on average, whereas the lifetime with Lithium & Alkaline packs can be more than 150 cycles (Fig.1). The battery voltage exhibits a fast drop almost in the entire lifetime of those floats with Alkaline packs, while this quick drop in battery voltage is only found after 150 cycles or as much as 200 cycles with Lithium & Alkaline packs.

      According to our analysis, Lithium packs is highly recommended to installed in each Iridium APEX float before deployment, which is able to prolong float s lifetime as much as 250 cycles. The cost of Lithium packs installation will be about 12,000 RMB.

Fig.1  The evolutions of the battery voltage for 35 Iridium APEX floats