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Troubleshooting
There are 26 ways to improperly connect two packs to a charger! After the Start/Stop button is
pressed, a special battery checking sequence automatically checks every wire before closing the
internal switches (if discharge wires are not used during charging). It is possible to get an unre
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lated safety code from a simple wiring issue.
Operating errors appear as messages in the display. To determine the problem, look up the de
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scription below. Correct the error. If errors continue, contact FMA Customer Service.
Message Problem
Neg. Term. < 0V Black banana jack is reading below 0 volts
Supply <10 Volts Low input supply voltage
Supply >16 Volts High input supply voltage
Supply Unstable Possible thin supply wires. Set input current limiting with Charge Control
Software.
Ch2 No Add Up Cell verication failed
Chg. Overvoltage Cell is over voltage
Bad Mode Number Internal software check
Series Chrgrs? Check that two chargers aren’t charging a series pack
Chg Overcurrent Check for a stable input supply
Bad FET Supply V Internal 55V supply is bad
Cell < 0.1V Low cell voltage
Bad MUX Cell Cnt Internal software check
Node 10 < 0V Last node wire is reading negative voltage
Bad EEPROM Wrt Internal software check
System Softstart Check for good power supply leads
2 Pack Con. Err Check pack wiring
Ch1 No Add Up Cell verication failed
Charges 12hr Max Charger timeout
Bypass Overvolt Check node wiring
Chgr Temp. >160F Make sure the fan is working
Check Pos. Term Positive terminal not connected
Amps Too Low Internal software check
No Plug Blocker Plug Blocker required, but not installed
C2 Pack Detected Pack was added to Ch2 while charging
Ch1 Pos < 0.5V Check node wiring
Low Voltage Cell Cell did not recover after 5 minutes of charge
Ch1 Bad S. Count Cell count cannot be determined; check for a cell < 0.5V
Ch1 has no Pack Pack must be installed on Ch1
Reverse Polarity Check wiring
Ch2 Bad S. Count Cell count cannot be determined; check for a cell < 0.5V
Node 5 < 0V Check node wiring
Understanding the Cellpro 10s Charger
You can set the Cellpro 10s Charger’s charge rate to one of three Auto modes—1C, 2C or 3C—as
appropriate for the pack(s) being charged. When one of these rates is selected, the charger
determines the pack’s capacity and automatically sets the correct output current using FMA’s ad
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vanced Fuel Gauging technology. You can also manually set charge current to any value between
0.1A and 10A in 0.1A increments. Finally, you can select Storage Charge mode which charges
to 50% rated capacity using Fuel Gauging technology. The charger handles multiple chemistries
and charge parameter presets.
When one pack is connected to the charger, the pack is intially charged at the selected charge rate
(or the maximum charge rate possible). Using Ohm’s law, the maximum charge rate (Amps) is
derived from the maximum power (Watts) the charger can produce without overheating.
Maximum power is approximately 300W measured at the charger input (FMA rates maximum
power using a 15V DC input source). Maximum power depends on many factors including pack
imbalance during charge, input (supply) voltage, output (charge) voltage, DC/DC converter ef
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ciency(whichvariesbetween80%and90%dependingontherelationshipofsupplyvoltage-to-
charge voltage), ambient temperature, and internal operating temperature.
Whenthepackreachesabout90%capacity,thechargerentersbalancechargemode.Chargecur
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rent tapers off, but will remain at 1A or higher until the pack voltage slows the current to 1/20th
C (Constant Voltage Mode). At this point, the pack is full and the charger announces “Charge
Complete” on the display.
During the entire charge process, the charger power balances the pack using 1A current until
all cell voltages are within 1mV of each other. Power balancing is the process of beginning the
balancing process early in the charge cycle using high current to shunt excess cell voltage while
other cells in the pack have a chance to catch up. Power balancing means the pack tops off faster
and the total charge time is greatly reduced. This is possible because the balance circuitry is in
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ternal to the charger, unlike some other chargers. Automatic temperature control and an integral
fan ensure the charger never exceeds maximum safe operating temperature under any conditions.
The result is faster, safer charge times.
When charging two packs, the packs are connected in series using four electronic switches inside
the charger. In effect, the charger treats the two packs as a single pack. (For example, if you
connect a 3s pack and a 4s pack, the charger operates on them as one 7s pack.) If the pack ca
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pacities are different for the two packs connected, the charge rate should be selected based on the
lower capacity pack. Initially, the packs are charged at the selected charge rate (or the maximum
charge rate possible) until one pack becomes fully charged—however, the charger handles cell
balancing of the two packs completely independently. The second pack continues to be charged
at a minimum of 1A charge rate until it is full and balanced.
Notice that one of the packs in a simultaneously charged pair is always topped off at a minimum
rate of 1A (dictated by the maximum balance current available). If the packs have the same
capacity, and were discharged to about the same level, both packs will charge in less than 30 min
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utes at 3C. However, if the packs have different capacities, or were discharged to different levels,
charging for the pair could take longer than expected. Since the charger supports fast balance
current of 1A, all other things being equal, the charger still outperforms competing brands. In
mostinstances,bythetimetherstpackisfullycharged,thesecondpackisalreadyapproaching
constant voltage charge mode; the battery pack itself is the limiting factor in charge time, not the
charger.
Example 1: You are powering an aircraft with two 4s 2100mAh packs connected
in series. Because those packs have the same capacity, and were discharged to
about the same level, you can expect them to charge in about the same time. It
would be appropriate to charge them simultaneously using the Cellpro 10s Charger.
