CELL RATING SPEC - Kokam 20mAh (4C)

1. The primary guideline for use of Li Po cells and packs is the discharge curve below, based on test of a statistically valid sample of production cells. All tests are at room temperature with no cooling to the cells so that all ratings are conservative. Please read the section "How to Use Li Po Batteries Effectively" of the Li Po Handbook to learn the effects of failure to operate Li Po batteries below 140 Degrees F. The C-rate promoted by some vendors is meaningless without knowing the temperature reached by the inner cells at those C rates.

2. There are four curves in the set that define cell rating:

• C-Rate 1 Capacity rating: Cell capacity is set by international standard at a discharge rate of 0.5 times the specification capacity of the cell. For example, 0.5C for a 2000 mAh cell is 1 amp. Capacity for any cell of any chemistry will be reduced more or less as discharge rate is increased. The rate of reduction of cell voltage is called "Voltage depression".
• C-Rate 2: Maximum continuous rate. The discharge current that the cell can deliver continuously without failing immediately. Recommended only for applications where it is absolutely demanded. Cycle life is not more than 50 cycles at this rate; about the same as for Ni Cd or Ni MH at extreme high rates. This is the "advertised" C-Rate that is also called "burst rate". WARNING: operation for even one run at > 170 Deg F can shorten life to just a few cycles.
• C-Rate 3: Maximum Life rate, continuous. Maximum average discharge rate for cell temperature to stay below 140 deg F at an ambient temperature of 68 Deg F. This rate will produce no degradation in life cycle as measured at 0.5C in statistical tests.
• C-Rate 4: Maximum Life rate, cyclic. Maximum continuous discharge rate that maintains cell temperature at or below 140 Deg F. This is the rate the cell will be operated at most times. As a rule of thumb, this may be estimated at 70% of C-Rate 2. The maximum "burst rate" may be much higher than C-Rate 2 for very brief periods (less than a second) so long as there are periods of discharge rate less than average that allow the average to be held.
  

HIGH CELL TEMPERATURE BRINGS SHORT CYCLE LIFE.
USE TEMPERATURE SENSORS TO KNOW : TMP-86/140-R or TMP-140-N