Li-Ion cell packs as sailplane flight packs?

[MarkERoberts]

Hi All:

Looking for some advice regarding the use of Li-Ion cells as sailplane flight packs. I have a 650 mah cell phone battery that is very small and light. It is only a 3.6 volt cell. I know that the only Li-Ion stuff I have seen is 3.6 per cell and a regular Ni-cad / Ni-Mh 4 cell flight pack is normally 4 cells at 4.8 volts. I am flying a One Design racer that has a smaller front fuse nose and I would like to put a smaller pack in the front. I am currently using a 4 cell Ni-Cad 270 mah pack, and am wondering about using the Li-Ion packs for sailplane set ups as they are smaller, lighter and have more mah than the Ni-cads or NiMh packs.

Here are my questions:

1. What concerns should I have using 3.6 volts with a Hitec 555 (or other for that matter) receiver?

2. Is the only real problem at a lower voltage that the servos will respond more slowly? What about torque?

3. If you use the Li-Ion cell packs, do you have to worry about the "explosion factor" like you do with the Li-Metal packs that have the little circuit boards on them to current overloads?

4. Any other advice for this set up?

Thanks to all!

Mark Roberts

[aeajr]

I am speculating here but:

At 3.6 V, if your receiver works at all it may have a greatly reduced range.

At 3.6 V the servos would probably have a lot less power and might have trouble moving your surfaces.

One solution would be to use an Electronic Speed Control with a Battery elimination circut. Then you could use two packs for 7.2 V and let the BEC feed 5 V to the receiver and servos. Since you would only be using the receiver side, you could probably use about the smallest ESC around so there would not be much of a weight concern.

All speculation my friend. If you figure it out, let us know.

[MarkERoberts]

Thanks for the reply! I had thought of using a small Pixie 7 speed control to reduce the voltage of the 7.4 volt Li-Poly or Li-Ion 2 cell cobo but I wasn't sure that would be necessary if the 3.7 volts would be sufficient to run the rig. I got a reply back from a couple of guys that said the voltage shouldn't be an issue, the servos will just run a bit slower. As I am building another smaller slope soarer, I am thinking of trying this set up. I'll report back if it works well! Thanks again for the reply! :)

Mark