Overview

This is my first time charging a LiPo battery, so this webpage is not the best place to learn about LiPo batteries.  Lithium Polymer batteries are extremely volatile and can easily explode if not handled properly.

Here is a link I highly recommend you read:

I’m using this blog as my own personal journal of my ‘heli-stuff’, so here we go.

My Battery

I purchased three lithium polymer batteries.  Here are the specifications:

  • Flightmax 2650 (www.zippybattery.com)
  • 22.2 volts
  • 2650 mAh
  • 6 cells (6S1P) = 6 cells, 1 in parallel)
  • 20C

So here are some key points:

  • Capacity:
    • Each cell puts out 3.7volts/cell.
    • My 6 cell battery puts out (6 cells x 3.7v = 22.2 volts) as its normal operating voltage.
    • The battery discharge a current of  2650 mA continuously for 1 hour, that is 2650 mAh.   This known as 1C for my battery.
    • The battery can discharge at a maximum rate of 20C, which means (20c x 2650 mA = 53 amps)!!  However at this rate, the 53amps would only last (60 minutes / 20C) = 3 minutes.
      • This is interesting because this shows that there is no point purchasing a battery with a discharge rate greater than 20C.  I can’t think of any application where you’d need to discharge your entire battery in 3 minutes.
  • Charging:
    • The charger needs to put 4.2volts/cell in order to push the charge in.
    • My battery would require  (6 cells x 4.2 volts = 25.2 volts) to charge.
      • Charge your battery “@ 1C”.  For me, my battery is a 2650 mAh, so I’d set my charger to 2.6amps.
  • Flying the helicopter:
    • My 6 cell battery will output (6 cells x 3.7v = 22.2 volts) during normal flying operation.
    • A LiPo cell is discharged when its voltage falls to 3.0 volts/cell.
    • My 6 cell battery is fully discharged at (6 cells x 3.0 volts) = 18 volts.  Time to land the heli.
      • This important to know when setting your ESC cutoff voltage.
      • You do not want the voltage to drop below 3volts / per cell….ever.

To summarize:

  • 25.2 volts – to push the charge in (@ 2.65amps)
  • 22.2 volts – normal flying voltage.
  • 18.0 volts – stop using battery, re-charge required.

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My Charger – Turnigy Accucell 8150

I chose this charger since it can charge….anything.  This battery is powered by a 12 volt utility battery.  I could have purchased a charger that plugs into a 120vac wall socket, however, you can’t use these at the airfield.  Whereas a 12volt battery is (sort of) portable.

It comes with lots of adapter cables.  Although, I had to create an adapter for the power supply with XT60 connectors to match my batteries as you can see in the above picture.

Turnigy Accucell 8150 Configuration

Please note – the following settings are specific to my batteries.  Your batteries may be different.   Remember, if you charge a LiPo battery incorrectly, it will catch fire/explode, so be careful.  Here are my settings:

Charger Parameter Value
LiPo V. Type 3.7v
LiPo / LiIo / LiFe CHK Time 10 min – max time charger spends checking battery prior to charging it.
NiMH Sensitivity Default
NiCd Default
Temp Cutoff 55 C.  Used for NiCd batteries, not used for Lipo.    I did put a temp sensor on my LiPo, never went above 19C.
Waste Time CHG>DCHG = 1 min (not applicable for LiPo)
NiMH / NiCd / Pb Trickle 50 mA
Safety Timer 90 min
Capacity Cutoff 2650 mA (matches my battery’s capacity).  Don’t push anymore that this amount.
Input Power Cutoff 10volts – input cutoff voltage.  Prevent draining your car battery below 10v.

Charging the battery

The thought of having one of these LiPo battery exploding inside my house or garage does not appeal to me.  I don’t want to put my family through that.  So, I charged the battery outdoors.

From the photo below, you can see I put the battery inside a cinder block.  If a malfunction were to occur and the battery catch fire/explode, it would be somewhat contained inside the cinder block.  To be totally safe, I should put the battery in a LipoSack or put a Ziplock plastic bag filled with sand on top of the battery.   If a fire breaks out, it will melt the plastic bag and sand will pour onto the battery smothering it.  Simple and very safe.

  1. Attach the Turnigy charger to the 12 volt car battery.
  2. Verify the Turnigy charger started up correctly and is working properly.
  3. Plug in the LiPo battery to both the charging plug and the balancing plug.
  4. Set the defaults settings as specified in the table above.
  5. Press the BATT TYPE button until you see  PROGRAM SELECT–> LiPo Batt
  6. Press the START button once.  You should see LiPo Balance 2.6A  22.2V (6S).
    1. WARNING: you must configure these settings to match your battery specifications.

Turnigy 8150 Accucell LiPo Balance

  1. Press the START button for 3 seconds to start the pre-charging process.
  2. At this point, you see the screen below.  The charger examines the battery to determine its characteristics.  In the photo below, it shows:
    1. R: 6 SER – the charger found 6 cells in the connected battery.
      1. Reported 6 cells in SERies.
    2. S: 6 SER – the number of cells you selected to charge in the previous menu.
      1. Set 6 cells in SERies in previous menu.
      2. NOTE – both of these numbers must be equal.  Otherwise you’ve configured incorrectly.  Go back and fix this.

  1. Press the START/ENTER button to confirm and start the charging process.  Now the charging starts.  The display will change and show the status:

Turnigy 8150 in LiPo Balance Mode

Configuration Amps currently being pushed into the battery Charge voltage being applied to the battery Elapsed Charging Time Total number of Amps that were pushed into the battery during this charge
Li6S 2.6 A 24.08 v 000 min 47 sec 00027

Li6S

0.8 A

25.20 v 019 min 29 sec 00709
Li6S 0.0 A 25.20 v 028 min 59 sec 00777

From the table above, you can see the progress of the charger over the 29 minutes it took to push 777 mA into my battery.  Since my battery can hold 2650 mA, this charge represented 777/2650 = 30%.

While it is charging, the buttons can be pressed:

  • INC – to see voltage of each cell.
  • DEC – to see charger configuration, input batter voltage and temperature sensor reading.
    • Internal Temperature = charger temperature.
    • External Temperature = temperature of the battery measured by the sensor.
  • STOP – stop the charging process.
  • ENTER – returns the display to the charging status screen.

I

The charger will sound an alarm to indicate the charge is complete.  At this point, you can press the INC button to check the voltage of each cell.

Internal is charger, external is the battery

As you can see, all cells charged to the same value:

  • C1 = 4.19
  • C2 = 4.19
  • C3 = 4.19
  • C4 = 4.19
  • C5 = 4.19
  • C6 = 4.20 (off by 0.01, too small to care).

Unplug the LiPo battery.  Unplug the charger from the 12volt battery.  You’re done.

Amount of Current to Power Turnigy

I put a current meter between the car battery and the Turnigy charger.  If you’re not charging a battery, the unit draws about 100mA.  However, when it first started charging, the Turnigy charger was drawing 6.7 Amps of current from the car battery.  This means that if you wanted to replace the car battery with an AC wall charger/power supply, it should be able to provide ~7 amps to the Turnigy charger.

Using the USB Port on the Turnigy Charger

Need to update this section with my screen rips….