7
2.7
Discharge
The Battery Unit BMS will switch to Battery Unit operation
within 10 ms of an interruption of power. In a similar
manner as for the charging, the BMS will terminate the
discharge before the Battery Unit reaches too low
voltages. The cut off voltage for the cell is 2.5V or if the
temperature exceeds the allowed limits (as specified in
section 2.4). The available discharge capacity is dependent
on current and temperature, see figure in section 2.3.
3
Useful Life
3.1
Cycle Life
The Battery Unit has a cycle life of more than 3700 cycles
before reaching EOL at 80 % depth of discharge (DoD), a
charge/discharge rate of 0.2C and at a temperature of
25°C. The cycle life is heavily dependent on the operating
conditions the Battery Unit has been subjected to. For
more shallow discharges (i.e. lower DoD) the cycle life will
increase, see figure.
3.2
Storage and Self-Discharge
The LITE Battery Unit has an expected calendar life of more
than 12 years. During storage, lithium-ion batteries will
gradually self-discharge. The rate of self-discharge increases
with increasing temperature and SoC. To maximize service
life, it is optimal to store the batteries at 30-40 % SoC in the
temperature range from 0°C to 25°C. However, storage
temperatures between -20°C to 60°C are acceptable.
Storage at temperatures above 60°C should be avoided due
to the increased safety risks associated with exposing
lithium-ion batteries to high temperatures. When the
battery is stored for long periods of time it is recommended
to regularly maintenance charge the battery, approximately
every 6 months, to prevent the voltage of the battery from
reaching harmful levels (below 2 V on cell level). The
following procedure should be used:
1.
Switch (CB) on the battery.
2.
Press the reset button marked RST. Hold for approx.
10s.
3.
Check SoC on LED indicators, marked Capacity.
a.
If two LED’s are lit, charging is not needed.
b.
If none or one LED indicator are lit, recharge
the battery until two indicators are lit.
4.
Switch off the battery (CB), repack the battery and
return to storage.
Number of cycles @ 25°C and 0.2C
Max. storage time vs temperature
DoD [%]
N
o
. o
f Cy
cl
es
Time [Years]
Te
mp
erat
u
re
[⁰
C]
