LiFe Receiver Batteries for SPA Airplanes
Part 1 - Why Switch from NiMH Batteries?
Jim Johns

Links to other articles in this series:
Part 2 - Battery Pack and Switch Modifications
Part 3 - Building Charge and Test Cables

I flew AMA pattern from 1982 through 2000, then took a 12 year break completely away from RC to do other things. I discovered that many things in the RC world had changed when I returned to flying in 2013.

  1. Radios had changed a lot. Most are now on 2.4 GHz instead of 72 MHz and onboard telemetry is available.
  2. Engines have changed too, and some of my old favorites are no longer the hot ticket.
  3. Batteries have come a long way. Most receiver – and transmitter - batteries are now NiMH (Nickel Metal Hydride) instead of the old tried and true NiCad (Nickel Cadmium) batteries we used previously.

I found these to be a mixed bag of changes. The first two are good things because they make our lives easier as modelers. Telemetry on my new 2.4GHz radio has saved airplanes twice for me in less than a year by detecting battery problems before they caused a crash.

Unfortunately, I can’t say the same for NiMH batteries. While they are rugged and provide strong power for our models, they have at least one negative trait – they self-discharge. This means that if you leave your models unused for an extended period of time, such as over the winter, you’ll find the receiver batteries very low or completely dead when you want to go flying again. Therefore, you have to recharge them approximately monthly while not in use to keep this from happening. I currently have five flyable aircraft in my stable and I wanted a better solution.

I had been using 5 cell 6.0 volt 2000 mah Hydrimax NiMH packs in my SPA competition aircraft to deal with the higher voltage and current requirements of digital servos. I did a lot of online research and found that a lighter 2 cell 6.6 volt LiFe (Lithium Iron) battery pack could be used to replace the NiMH pack without adversely effecting either my JR XG8 radio or DS821 servos, so I changed one of my aircraft over to a LiFe receiver battery to see for myself. The results were amazing – the LiFe pack held a charge for a very long time, wasn’t affected by the high current draw of my digital servos and could be charged very quickly. I did find three drawbacks to changing to the LiFe receiver batteries.

  1. They require a different charger since they have an entirely different charging regimen than NiMH batteries.
  2. They need to be balance charged, meaning both cells should be charged to equal voltages. I’ve read that if they aren’t regularly balance charged, it decreases their performance and shortens their lifespan.
  3. You need a battery checker to verify the state of charge of each individual cell of the LiFe pack.

Item 1 is pretty straight forward – simply buy a new charger. It’s a one-time expense and decent DC only chargers are available for under $30 while an AC/DC version can be found for around $70. Below is a table showing three chargers that I personally own and recommend. All will balance charge your battieries without problems.

Item 2 and 3 are addressed on other pages. Click the links at the top of the page to visit.

Hitec X1+ AC/DC charger : This is a basic charger that will do everything you need to do. It’s very versatile - it will charge, discharge and cycle batteries of many different types (NiMH, LiFe, LiPo, etc) and can be powered by 110 volt AC at home or 12 volt DC (car battery) at the field. It's usually under $70 from Tower and other sources.
SkyRC IMAX B6 charger (DC only): This charger is very similar to the Hitec above, except that you need a DC power source. You can use either your car battery or a 12V DC power supply.

IMPORTANT NOTE: Be very careful of cheap knock-offs of this charger not made by SkyRC. Google “Imax B6 charger problems” to see some of the problems associated with these cheap imitations. Watch the video on the Hobby King page at the link below for identification information. I bought my "real thing" for under $30 from HobbyKing.com.

Genuine SkyRC Imax B6 Video
ICharger 106B or 206B: These are more advanced, higher quality versions of the B6 above, and are also DC only. The 106B charges at a maximum of 10 amps while 206B charges at 20 amps max. Both are quite small and work very well, but you’ll need a DC power supply to use them at home. I bought my 206B from Grayson Hobby near Atlanta for under $100.