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Charging tips
General information
Cells in a pack have different voltages when they are discharged. GT1000 balances
(equalizes) cell voltages while it is charging the pack. GT1000 provides one of the highest
available balance current in the industry.
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.
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 GT1000 will still balance them by the end of charge. For this
reason, it may take longer to balance older packs. The charger may show FUEL=99% for
some time while it is balancing a high capacity (3Ah and up) “veteran” pack that is severely
out of balance, but some settings can be configured to stop balancing after a preset time or
condition. Often, the last few millivolts of balancing take a very long time and do not
significantly improve overall pack charge or performance.
Charging packs
You can top off packs, or remove them when they are partially charged. There is virtually
no way to damage a pack when using GT1000. (The only exception to this is if you are
using Parallel Adapters and you accidentally connect two packs having different number of
cells together in parallel. This is less a function of the GT1000 and more about ensuring
proper connection of packs to the GT1000.)
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 over-discharge the pack
during the flight. Auto-detect speed controllers should properly set cut-off voltage if packs
are charged to at least 90%.
To save time, stop charging when the pack reaches about 95% of capacity. That last 5%
takes the longest.
Some cells may sag 0.10V within an hour after charging. This is normal as packs age.
In REVOLECTRIX’s opinion, over-discharging an LiFePO4 (or A123) pack below 2.0V/cell
will damage the cells (contrary to some reports). GT1000 requires a minimum pack voltage
of 1.5V to activate charging. If an LiFePO4 (or 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 GT1000 will reject it for multiple reasons (as indicated by
displayed messages).
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