Estimating Performance Factors - FMA Cellpro Multi4 Manual

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Estimating performance factors

If you don't have a way to directly measure your propulsion system's electrical parameters, the
Cellpro Multi4 Charger enables you to estimate them using before- and after-fl ight measure-
ments.
1. Collect data
a. Charge pack.
b. When charging is fi nished, record Fuel % and total pack voltage (i.e. sum of cell volt-
ages).
c. Fly plane (or test on the ground). Record fl ight time in minutes.
d. Connect pack to charger. Record Fuel % and total pack voltage.
2. Calculate performance factors
(Fuel % before fl ight) – (Fuel % after fl ight)
x (Pack capacity, Ah) = Capacity consumed during fl ight, Ah
100
(Capacity consumed during fl ight, Ah) x 60
= Average current during fl ight, A
(Flight time, minutes)
(Pack voltage before fl ight, V) + (Pack voltage after fl ight, V)
2
(Average voltage during fl ight, A) x (Average current during fl ight, V) = Average power during fl ight, Watts
(Average power during fl ight, Watts)
= Watts per pound
(Model weight, pounds)
The "LiPo Performance Estimator" spreadsheet, which simplifi es these calculations, can be
downloaded from www.fmadirect.com/tech_data/techdocs/.
3. Evaluate results
 Average current during fl 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 fl ight may greatly exceed the average current you calculated.

Watts per pound is an approximate indicator of aircraft performance (other factors infl uenc-
ing performance include lift, drag and motor type). Here are some guidelines:
 25 to 30 watts per pound: level fl 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 voltage during fl ight, V
Charging a pack
As shipped from the factory, the Multi4 Charger is equipped with 20 User Presets optimized for
common battery types, plus fi ve Empty Presets. In many cases, you can simply select the User
Preset that matches the pack you want to charge, connect the pack and start charging.
User Presets cover LiPo, Li-Ion, A123, NiCd, NiMH and Lead Acid chemistries paired with
commonly-used charging strategies. (If the User Presets aren't quite what you need, see the in-
structions beginning on page 6.) The charger also includes a Preset Library containing up to 50
presets. A Library Preset is like a User Preset, except that it must be loaded into the User Preset
bank before it can be changed and used for charging (see "Loading a Library Preset," later).
1. Connect the charger to a 12V to 16V (maximum), 5A power source. You can connect the
pack any time between now and step 4.
2. The fi rst screen you will see is the Welcome screen. Press and release the Mode button to
display the Preset Menu.
Tip: More information about the display —and how to navigate it—is provided on the
next page.
3. The Preset Menu displays last User Preset you used. If this is the User Preset you want to use
to charge the pack, go to step 4.
otherwise
Press the Mode button until the User Preset you want is displayed (see "Factory-installed
User Presets" for descriptions). (If you see EMPTY PRESET, press the Mode button to go
back to the beginning of the list.)
Tip: Quickly press and release, press and hold, then release the Mode button to re-
verse the sequence of items being displayed in the Preset Menu. The tone indicates
which direction you are going: high tone for forward, low tone for reverse.
4. If the pack isn't connected to the charger, connect it now.
5. Press and hold the Mode button. This displays the Operations Menu, which cycles through
several screens. When you see START, release the Mode button.
6. The display will briefl y show CHECKING PACK.
7. The next screen displays the preset's chemistry (for example, LiPo) and prompts you to
verify it is the same as the pack's chemistry (which should also be, for example, LiPo). This
safety check is your chance to prevent charging if the preset and pack don't match.

If the displayed chemistry matches the pack's chemistry, press the Mode button to start
charging. Go to step 8.
or
 If the displayed chemistry does not match the pack's chemistry, do nothing. The screen
will time out, and you will be returned to the Preset Menu. Go to step 3.
8. During charging:
 Press the Mode button to view various charging data screens (the number of screens and
the data displayed depends on how the User Preset is confi gured).
 To stop charging:
a. Press and hold the Mode button. You'll see Stop Charge? >No.
b. Press the Mode button to see Stop Charge? >Yes. Press and hold the Mode button.
c. You'll see CHARGER STOPPED. Press the Mode button to go to the Preset Menu.
9. When charging is complete, the charger will "beep beep beep" several times and the display
will show ELAPSED [time] / [chemistry] DONE. Press the Mode button to review
charging data screens.
10. Disconnect the pack from the charger. The screen displays PACK REMOVED.
11. Press the Mode button to return to the Preset Menu. The charger is ready to charge another
battery.
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