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4 17
Example 2: You are powering one aircraft with a 3s 500mAh pack, and other air-
craft with a 5s 5000mAh pack. If you charge these packs simultaneously using the
Cellpro 10s Charger, it would probably take a long time (the 500mAh pack would
becomefullrst,thenthechargerwouldswitchtoits1Abalancingratetollup
5000mAh pack, which could take several hours). In this case, it would be faster
to charge these packs separately because the charger can then apply optimum (and
substantially different) charge currents to each pack.
In some cases, such as Example 2, it will be faster to charge two packs separately rather than
simultaneously. It’s up to you to decide whether to charge two packs individually or as a pair,
based on what you know about their respective capacities and discharge states.
The Cellpro 10s is equipped with FMA Fuel Gauging technology. During all phases of the
charge process, the charger will report the fuel level of two packs being charged independently.
In Example 2 above, when the 500 mAh pack reaches 100% capacity, it is a simple matter to
remove the pack from the charger and continue charging the 5000 mAh pack at a higher charge
rate. Here’s the full procedure:
1. Connect both packs and start charging them at an Auto rate.
2. Watch the fuel level display. When one pack reaches 100% fuel level, stop charging.
3. Disconnect the full pack.
4. If the partially charged pack is connected to Channel 2, move it to Channel 1.
5. Continue charging the partially-charged pack.
Charger input current limiting
The charger will draw up to 25A to deliver its 10A maximum output current. The high input cur-
rent is required when the input voltage must be boosted to drive packs having larger numbers of
cells in series. The charger’s algorithms are based on power, not current. The charger initially
draws 300W, but will automatically reduce power consumption based on its internal temperature.
Output power is determined by several factors, including battery pack imbalance during charge,
input voltage, input current, output voltage, ambient temperature, and the charger’s internal tem
-
perature.
Thecharger’sDC-to-DCconverteristypically80%to90%efcient.Highestefciencyoccurs
when the input voltage is higher than the output voltage needed to charge the connected pack(s).
However, the charger cannot tolerate input higher than 16V. Setting the input voltage to 15V pro
-
videsthehighestefciency,coolestoperatingtemperatureandfastestchargingtimes,especially
whenchargingpackscontainingmorethanvecellsinseries.
You can also manually limit the charger’s input current so the charger will not draw more power
than the supply can provide. If you know your power supply is rated for 3A output, for example,
you can limit the charger’s input current to 3A. (Be aware that limiting charger input current
may increase pack charge times.) When the charger is powered from a high current source (such
as a car battery), you can override manual current limiting to provide maximum pack charging
current. Details are provided in “Limiting charger input current” in the “Using the Charge Con
-
trol Software” section of this manual.
Estimating performance factors
If you don’t have a way to directly measure your propulsion system’s electrical parameters, the
Cellpro10sChargerenablesyoutoestimatethemusingbefore-andafter-ightmeasurements.
Collect data
Charge pack.
Whenchargingisnished,recordFuel % and total pack voltage (i.e. sum of cell voltages).
Fly plane (or test on the ground). Record ight time in minutes.
Connect pack to charger. Record Fuel % and total pack voltage.
Calculate performance factors
(Fuel % before ight) – (Fuel % after ight)
100
x (Pack capacity, Ah) = Capacity consumed during ight, Ah
(Capacity consumed during ight, Ah) x 60
(Flight time, minutes)
= Average current during ight, A
(Pack voltage before ight, V) + (Pack voltage after ight, V)
2
= Average voltage during ight, V
(Average voltage during ight, A) x (Average current during ight, V) = Average power during ight, Watts
Evaluate results
Average current during ight gives you a rough idea whether system components—ESC,
motor, connectors and wiring—are operating within their current ratings. Keep in mind that
peakcurrentduringightmaygreatlyexceedtheaveragecurrentyoucalculated.
Watts per poundisanapproximateindicatorofaircraftperformance(otherfactorsinuenc-
ing performance include lift, drag and motor type). Here are some guidelines:
25to30wattsperpound:levelight.
40 to 50 watts per pound: take off from smooth surface, climb.
50 to 75 watts per pound: take off from grass, sport aerobatics.
75 to 125 watts per pound: pattern aerobatics.
Over 125 watts per pound: 3D.
Tip: For more direct electrical measurements, consider these FMA products:
60A Current Shunt (Model DVM-SHUNT-60)
Digital Multimeter (Model DVM-VC890D)
(Average power during ight, Watts)
(Model weight, pounds)
= Watts per pound