18650 LiIon batteries as receiver packs

I had an issue recently with my receiver packs which was caused (I believe) by my lack of understanding regarding the do's and don'ts of batteries.
I had heard people talk about cycling their battery packs to give them a bit of a tidy up and with my fancy-pants charger I set the packs to do 3 cycles.
What I didn't realize is that you should never discharge batteries below certain voltages and I set the cycle to 0.0v. I also left the battery packs in my drawer and fuselage (disconnected) for about 3 years of inactivity. 
This short story is becoming a tad lengthy, so to wrap it up, the 4 cell NiMh battery pack failed recently leading to a catastrophic meeting of terrain and a baffled Aussie. What the heck had happened? What had I done?

After some research and some advice, I chose to install the same set up as Reto Blumer with 2 x 18650 LiIon batteries (Panasonic NCR 18650PF 2900mAh). These two batteries deliver 8.4V fully charged when configured in series which is a bit too much for standard servos requiring the voltage to be dropped down by the time it gets to the servos.

There were 2 options for doing this. The first was to install UBEC's  in the wiring of the wing and fuselage just prior to the servos that converted the high voltage to 5V, guaranteeing to not burn out your servos. This option also allowed your receiver to receive the entire voltage from the pack which is excellent if you have telemetry sent to your transmitter with battery voltage.
Even though the ground had kindly disassembled my wing and given me access to the wiring, I chose to install a single UBEC before the receiver which converts the voltage to 5V (you can choose 6V if you like). This negates my in-built telemetry for battery voltage (I can buy a sensor to give the telemetry back) and also creates a little headache for the fuselage installation with 2 issues.

The placement of the UBEC can interfere with the operation of the receiver. There is some techo reason for this, but it is irrelevant really. The fact is that you need to have the UBEC far enough away from the RX to allow proper function. this took some significant jiggery-pokery, but I did manage to achieve it! The second issue is the additional space required.

All the figuring out is worth it in the end though as I now have ample battery supply and power and a new, embedded charging regime. I also have a little voltage meter which which I can check the voltage of the pack before or after each flight.

I have done some more research on the batteries and I think I'll stick to the Panasonics and continue to get them from ECOLUXSHOP on Ebay. I got lots of information from The Battery University which I found I could understand after reading it a few times. The UBECS are available from T9Hobbysports for the inline ones for individual servos and the Single UBEC for the entire system I got from First Person View. One of my Skorps didn't have a switch so I got a magnetic one from Rich at T9 as well. I also mad a very cheap and basic voltage tester by soldering two male servo pins onto the wires of this.

I found a good list of precautions regarding LiIon batteries that I'd like to share with you here:

Never completely discharge li-ion battery ( below 2.5V ).Charge fully before first use.Never use force to install (insert) li-ion battery.Use only high quality battery chargers.Do not expose to heat. Do not short (connect) positive, and negative battery contacts. (Keep battery that is not in use in plastic holder)Do not charge battery over 4.29V (another reason to use good battery charger).Do not charge unattended.Do not store your li-ion batteries fully charged (for extended period of time).Store in cold and dry place at approximately 3.7V (storage charge).Never try to charge (or discharge) li-ion batteries with battery chargers that are not made for Li-ion batteries.- See more at: http://www.orbtronic...h.lECsV2VZ.dpuf


Hopefully some of this info will be helpful for you, however please remember that I am by no means an expert and am not trying to tell you how to set up your power supply for your planes. Copy my set up at your own significant risk!!