LiPo for 3DR IRIS R/C transmitter

IRIS pilots will quickly get tired of buying Alkaline AA batteries for the R/C transmitter and will also realize that this can turn into a costly part of our hobby. Time to replace these batteries with a Lipo.

Required materials and tools

The following materials are required.

The following tools are required:

  • Very small flat-head screwdriver

How-to assemble

Important: The discharge leads of the above pack is reversed for the use in the 3DR IRIS R/C transmitter. Read these steps carefully to fix this!

Follow these steps to change the polarization of the above LiPo and install it into your RC transmitter:

  • The Turnigy 2650mAh 3S 1C LLF Tx Pack comes with 3 leads that can be used for charging and discharging (See Figure 1). Lead 1: Balance lead for charging. Lead 2: Discharge lead for R/C controller (More later). Lead 3: Charge lead.

    Figure 1: Lipo Charge/Discharge Leads

    Figure 1: Lipo Charge/Discharge Leads

  • For the discharge lead (See Figure 1, Lead 2.) use a very small flat-head screwdriver and carefully remove the metal pins from the plastic plug. As an alternative you can also use the Futuba plug (See Figure 1, Lead 3) and place the battery sideways into the bay.
    Important: Ensure that the metal pins don’t touch each other! This will shorten the battery and can cause damage.

    Figure 2: Removing the metal pins from underneath the plastic clip

    Figure 2: Removing the metal pins from underneath the plastic clip

    In Figure 2, Sequence 3 you can see circled in red the small barb on the metal pin. You need to carefully lift the plastic tooth under which the metal pin is locked in (See Figure 2, Sequence 1). While lifting the plastic tooth you have to carefully and gently pull the wire towards the back (See Figure 2, Sequence 2).

  • Notice that you can only insert the plug of the discharge plug in one way, with the plastic locking the pins facing down. Re-insert the cables, so that the red wire is on the right and the black wire is on the left, while the plug is facing down with the plastic locking mechanism (See Figure 2).

    Figure 3: Discharge lead of the LiPo

    Figure 3: Discharge lead of the LiPo

  • Insert the discharge plug into the 3DR IRIS R/C controller. Red (+) on the middle pin and Black (-) on the left pin (See Figure 2).
  • Place the Lipo inside the 3DR IRIS R/C controller to the right of the battery bay and store the remaining cables.

    Figure 4: Lipo stored in 3DR IRIS radio

    Figure 4: Lipo stored in 3DR IRIS radio

  • I placed a small strip of foam between the Lipo and the battery door, before closing the battery door. When doing so, be careful to not squeeze any of the cables.


While Lead 2 is connected to the R/C transmitter, Lead 1 and Lead 3 are not (See Figure 1). This means that you can charge your radio Lipo via Lead 1 and Lead 3, while the Lipo is in the R/C transmitter and without disconnecting Lead 2. Just open the battery door, carefully remove Lead 1 and Lead 3 and connect them to your charger. Ensure that your R/C transmitter is turned off while charging.


The 3DR IRIS R/C transmitter is a re-branded Flysky / FrSkY transmitter and usually works with 12V (8x 1.5 AA cells). With the backlight installed it needs about 120-140mA. Since the above Lipo provides 12.6V when freshly charged, you might be scared by this difference. No need for this as the voltage will drop pretty fast below 12V.

In contrary to some of the other proposed batteries, this Lipo can be charged with the stock 3DR charger or any other Lipo charger.

You will notice that the R/C transmitter becomes very lightweight with the Lipo installed. Also with 2650 mAh it will last for month on regular flying.

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18 comments on “LiPo for 3DR IRIS R/C transmitter
  1. stevenching says:

    Great info! Was looking for a solution to the heavy batteries.

  2. jsolderitsch says:

    I have not yet reversed the pins for the RC Controller connector — I did notice they were reversed. But the Futaba plus also works to connect to the transmitter. This is mentioned here: at the Update 8 position in the long article.

  3. jsolderitsch says:

    The battery actually fits sideways when using the Futaba plug and seems snug enough. The battery door still slides on OK.

  4. jsolderitsch says:

    I don’t see what action I should take with the screw driver to remove the metal pins — are there any pictures or instructions I can follow?

    • jsolderitsch says:

      Ooops — I was trying to lessen some of the pressure on the plug end to extract the wire and I must have caused a brief short — saw some sparks! And the white plug was a little misshapen after that. I got one of the wires out but could not budge the other. So I just cut the leads individually and put some heat shrunk tubing on the ends and will just use the Futaba plug for charging and in the transmitter. The battery seems fine and I put it in the charger and re-charged until I got a green condition on the charger indicator — e4 SkyRC charger — what came with the Iris. Transmitter seems to be fine as well. Will watch the voltage level carefully while in use in the transmitter.

    • I added some additional pictures and a better description. Hope that helps.

      • jsolderitsch says:

        Yes — definitely helps. Turns out this was what I was trying to do but I was using a thin knife blade rather than a thin screw driver and I must have bridged the connection with the knife between the pins. I need a non-conductive blade I guess. Or more patience…

  5. Kent Hammerstrom says:

    Christian Elsen…your posts are great especially for a UAV newby like me…keep up the good work! I have a question about this post: I bent the tab too far trying to remove the power lead so I need to replace the connector…can you post a description of the connector or a link to a web store to purchase some connectors? Thanks

  6. Joe Homer says:


    Thanks for the very explicit and clear discussion on using a lipo in the FS-TH9x transmitter.

    Don’t you know that however clear your instructions are sooner or later some idiot is going to fuck it up?

    Just in case someone does screw up can you tell us what part is it that burns up and smells so badly inside the transmitter. Also is it some element inside that the dumb-ass can replace and restore his radio to some semblance of usefulness?

    How would said idiot wire-up some circuit that would prevent future damage if he repeated his mistake in another life time .

    Thanks. Keep up the good work.

    Joe Homer

  7. APOC says:

    can you tell me if can I use Gens Ace 2600mAh 11.1V TX 3S1P Lipo Battery instead of the Turnigy? can’t find that exactly battery so Im looking for alternatives

    • Christian Elsen says:

      You can probably use that Lipo as long as you can physically fit it into the battery compartment and make the wiring work.

      But the battery that I referenced is a LiCo, not a LiPo. It’s built with a low C-rate Long Life LiCo Formular which isn’t like a standard LiPo. It retains voltage for months on end without need for a storage charge so you can store your radio and fly once a month and not have to worry about discharging or recharging your pack.

  8. SteveHookEm says:

    Adam at Black Ops Drones sells a drop in LiPo with the correct connector. It’s ready to go.

  9. Joe B says:

    Just an update… I purchased my iris+ in February 2015 and they have since changed the connector. I was able to simply match the red with the red and black with black and push the connector onto the xmitter. while not a true fit it is tight enough that it will not come off during use and easy enough to remove for charging. Just have to pay attention when connecting. thanks for info

  10. David says:

    In haste one flight I plugged the Lipo Connector in reversed. There’s that smell that @Joe Homer spoke about. Further inspection… Main board, looks like a diode or rectifier. Ohh boy dead Radio. Maybe time for a Taranis?

    • Joseph W. Homer V says:

      In haste one flight I plugged the Lipo Connector in reversed. There’s that smell that @Joe Homer spoke about. Further inspection… Main board, looks like a diode or rectifier. Ohh boy dead Radio. Maybe time for a Taranis?


      I found a Youtube video on ‘RCmodelreviews’ in which Bruce Simpson (??) demonstrates repairing a burned up FS-TH9x transmitter. Not an easy soldering job but probably a good exercise in the DIY spirit. I am in the middle of trying to fix my own transmitter but went ahead and bought a Taranis because of its’ improved stuff. There’s more info elsewhere on curing this problem but I’ll have to hunt for it if you are interested. Good luck!

      Joe Homer