3.2.1 Designed Capacity
This should be set to the battery pack’s capacity, in amp hours (Ah). It is not used to calculate the state of
charge. It’s simply used when displaying the intended capacity of the cells. The actual capacity of the pack is
defined as the cycle capacity, which is described in the next section. Designed capacity can be calculated as
follows:
esigned capacity ell capacity arallel cell count of packD = C × P
NOTE: This parameter is displayed in milliamp hours in the iPhone app.
3.2.2 Cycle Capacity
This parameter is used to calculate state of charge. In the real world, batteries do not meet the designed
capacity printed on the cells. It can be higher, if the cell was underrated, or it can be lower (especially true for
used or B- or C-grade cells).
Ideally, the capacity of the battery pack should be measured, and the actual number should be programmed
into the BMS. Therefore:
ycle capacity ctual measured capacity of the packC = A
There are several ways to measure the pack’s total capacity. The easiest way is to set the cycle capacity to
hook a known DC load up to the battery, and measure the amount of time it takes from full charge down to
cutoff. Ensure that the protection parameters are set before starting. Charge up to 100% (see the section on
top-balancing). Note the start time. Record the pack voltage in 15 minute intervals (this info may be used to
set the percent capacity voltages, later in this section). Record the time when the BMS protection circuitry
cuts off the discharge current.
ycle capacity T est load current (A) otal run time (h)C = × T
NOTE: This parameter only affects the state of charge. If it is set too low, the state of charge will hit zero
percent before the battery is actually at zero percent. The state of charge percentage will never go negative.
3.2.3 Full Charge Voltage
This should be set to the cell’s voltage at full charge. This information typically comes from the battery cell’s
datasheet, but the recommended values in Appendix A may be used.
3.2.4 End of Discharge Voltage
This should be set to the cell’s voltage and end of discharge. This information typically comes from the battery
cell’s datasheet, but the recommended values in Appendix A may be used.
3.2.5 Discharge Rate
Leave this at the default setting.
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