ProgressiveRC 4S Gold FMA Cellpro - Manual (Page 6)

6
Practical information about the Cellpro Charger
General information
n
Cells in a pack have different voltages when they are discharged. The Cellpro 4s Charger bal-
ances (equalizes) cell voltages while it is charging the pack.
n
During charging, cells that charge the fastest are the weakest cells in the pack. At the end of
charging, cells with the highest voltage are weakest. This happens because weaker cells have
lower capacity, and they charge faster than stronger cells.
n
If the Cellpro Charger displays LOW VOLT RESTORE, the pack was overdischarged during
its last use. The charger will attempt to repair LiPo cells measuring between 0.5V and 2.7V,
or A123 cells measuring 0V to 2.0V. To avoid additional damage to restored cells, do not
overdischarge a repaired pack.
n
By definition, end of life for a LiPo cell is when the cell can only be charged to 80% of its
original capacity rating. The number of charge/discharge cycles a cell undergoes before
reaching end of life depends on several factors, including cell quality, discharge rate, internal
heat generated during use, and other parameters. Cells in an older pack may be more out
of balance, but the Cellpro 4s Charger will still balance them to within 10mV by the end of
charge. For this reason, it may take longer to balance older packs. The charger may show
FUEL=99% for several hours while it is balancing a high capacity (3Ah and up) “veteran”
pack that is severely out of balance.
Charging packs
n
You can top off packs, or remove them when they are partially charged. There is no way to
damage a pack when using the Cellpro 4s Charger.
n
If a pack is at 80% or less of its capacity when connected to an auto-detect speed controller,
the controller may lower its cut-off voltage. This could overdischarge the pack during the
flight. Auto-detect speed controllers should properly set cut-off voltage if packs are charged
to at least 90%.
n
To save time, stop charging when the pack reaches about 95% of capacity. That last 5% takes
the longest.
n
Some cells may sag 0.10V within an hour after charging. This is normal as packs age.
n
When charging an A123 pack that has been discharged very low, the charger initially may
not be able to accurately count cells in the pack. To eliminate the possibility of an inaccurate
count, the charger applies current to “wake up” the cells, then recounts.
n
Overdischarging an A123 pack below 2.0V/cell will damage the cells (contrary to some re-
ports). The Cellpro 4s Charger requires a minimum pack voltage of 1.5V to activate charging.
If an A123 pack is below this voltage, do not try to repair the pack by boosting voltage. Even
if you manage to repair the pack, it will not have many cycles left and the charger will reject it
for multiple reasons (as indicated by displayed safety codes).
Storing packs
n
For best results, packs (except A123 packs) should be stored at 50% of capacity. Use the
charger’s Store Mode.
n
A123 packs can be stored at 100% of capacity (fully charged). In this chemistry, the break-
down voltage is higher than the fully-charged voltage.
CAUTION: Do not use the charger’s Store Mode for A123 packs. Store Mode applies
3.84V per cell, which will damage A123 cells.
n
Packs charged to 100% should not be cooled below room temperature. Cells at 90% or less
capacity can be cooled below 32ºF (0ºC).