RC Batteries

Hi Guys.

I recently started with a new project(35% Yak 54), and was looking at saving some weight somehow, without changing the strength of my airframe. That’s when I decided to do some research on batteries and the pros/cons of the different type of battery applications. I already knew and used the old Nicad/NiMH’s and didn’t want to use them as the weight and charging time on these batteries just doesn’t compare to some of the other options out there. The two options left for me were either Lipo or Life. Now there is nothing wrong with Lipo, but with it not being so save, and I’m not saying there is something wrong with it, if one charge them correctly and monitor them, then it is save enough, but still, for me it is a concern. So I started looking at the LifePO4 batteries and read some great reviews on them, and went through a few forums where it has been discussed and I must say from what I read people like these batteries a lot.

The pro’s:

• High power to weight ratio (almost as good as the LIPO’s).
• More tolerant to over and under charge/discharge.
• Almost no self-discharge, so you can charge today and fly next month (don’t know who would want to do that, but sometimes the weather / family duties can keep one from not getting to the field for quite a while).
• Can be used without regulators (3.3v per cell).
• Can be charged at up to 5C.

The Cons:

• It looks like the Lipo’s still has a bit of a power to weight advantage, but it is minimal.
• Need a Life(A123) capable charger.

I got my first Hyperion pack from Tino and Wayne at The Knife Edge Spin, which is a small 2cell 850 mAh 6.6v pack which I am testing out in a Hanger 9 Ultra Stick for now. They also supply the adapters for conversion to JR and Futaba. The 850 mAh pack only weighs 48g, with the adapter plug it weighs 54g, which is half of the NiCad pack that I removed from the same plane. I just removed the old one and added the new one, no need for any regulators etc. I discharged it, and then charged it at 2C and I must say, to be able to charge my receiver batteries in half an hour compared to 10 hours for my normal NiMH or NiCads, or the flameout concern’s of Lipo’s was really nice.(The battery can be charged at 4C or 5C aswell but 2C is sufficient for me, seeing as the battery would mostly only be half discharged in any way, so my charge time would only be 15min) These are just some of the benefits of the battery, but the real reason I started looking at other batteries were to save weight, and here are the specs:

G3 LiFePO4 Receiver Packs (Rx)
Part#	TYPE	Capacity	Max Current Continuous	Max Charge Rate (4C)	L x W x H (mm)	Weight (g)
HP-FG305-0850-2S	6.6V "flat"	850mAh	4.25A	3.4A	54.5 x 29.5 x 15.4	48.8
HP-FG305-1450-2S	6.6V "flat"	1450mAh	7.25A	5.8A	84.6 x 29.5 x 17.2	82.3
HP-FG305-1600-2S	6.6V "Thin"	1600mAh	8.0A	6.4A	89.5 x 49.8 x 9.2	89.0
HP-FG305-1700-2S	6.6V "hump"	1700mAh	8.5A	6.8A	53.6 x 30.4 x 31.2	94.4
HP-FG305-2100-2S	6.6V	2100mAh	10.5A	8.4A	95.0 x 30.3 x 18.1	106.0
HP-FG320-3000-2S	6.6V	3000mAh	60.0A	12.0A	131.3 x 35.5 x 19.8	193.5
HP-FG320-3800-2S	6.6V	3800mAh	76.0A	15.2A	133.0 x 42.4 x 20.4	240.6

I'm going to have 3 x 2100mAh, two for my servo's and one for ignition + 1 x 850mAh for the reciever. By using these batteries I will be saving just over half a Kg on my plane. That could be the difference between a nice palne and an excellent plane.

For some more info about these cells you can have a look at the following links:

http://www.rcmodelreviews.com/baffledbybatteries4.shtml

Have a look at the link below, you can see here what the packs look like.

http://media.hyperion.hk/dn/fg3radio