The ready light on the charger indicates that the battery is fully charged, ready to go. However, in no way does the ready indication guarantee sufficient battery capacity. Without checking the battery capacity on a periodic basis, the performance on some packs may eventually fall to such a low level that they barely endure a routine day. Even worse, most operators are oblivious to the fact that some of their batteries may be exhausted at the end of a work shift with no reserve energy to spare.
In many applications, weak batteries can hide comfortably because little demand is placed on them. The situation changes when heavy traffic is required during an emergency. Total collapse of mobile communications occurs too often and such a breakdown is mostly the fault of poorly performing batteries.
Carrying a larger battery does not necessarily mean increased capacity and better reliability. In Figure 17, five batteries of different sizes and with various conditions are charged. Batteries B, C and D show reduced charge acceptance because of memory and other deficiencies. The worst one is Battery D; it switches to READY after only 14 minutes of charge (assumed time only, real time may differ). This battery is a likely candidate to be picked when a fresh battery is required. Battery A has the largest capacity and hence takes longer to reach full charge than those with memory. Ironically, this battery will not be picked until the ready light comes on.
Typical charge times of batteries with different sizes and charge acceptances
* Estimated based on 0.5C charge rate for each respective battery size with assumed charge efficiency
When full charge is reached, the batteries are picked for field use. The first pack to go down is Battery D; its assumed discharge time is only 14 minutes. In comparison, the much smaller Battery E lasts for 60 minutes. The true winner is the medium sized Battery A with 120 minutes of assumed run time.
Discharge/Run times of fully charged batteries of different sizes and conditions
* Estimated based on 0.5C charge rate for each respective battery size.