For the electric Chrysalis you recommend a sperate battery for the recvier. Why can't (or shouldn't) I get the reciver power from my main Li-Po pack as can be provided by my controller?

From : Don Stackhouse

Because you can't predict with any accuracy or certainty how much capacity the motor has pulled from the battery, and therefore you can't predict accurately how much is left to run the radio.

Our conventional pure sailplanes and gas models use the radio battery only to run the radio. Since the radio's average power consumption rate is fairly low and reasonably constant over the long run, we can predict about how long the battery will last, then throw on a healthy factor of safety, and be reasonably sure that if we respect that limit, the radio battery will not quit while we're still in flight.

However, in the case of the motor battery in an electric sport sailplane, each motor run for launch or climb uses a big chunk of power, and we may have a number of runs of varying lengths on that motor battery during the course of one flight. Yes, when the battery finally gets to the end, the low voltage cutoff ("LVC") in the electronic speed control ("ESC") will sense this and shut down the throttle. Generally at that point there is at least a minute or two of battery life left.

Unfortunately, when the battery gets down to that level and triggers the LVC in the ESC, it's very possible that the model might be a thousand feet up and half a mile away in a thermal, with the motor shut off. The LVC will trigger, but you won't have any way of knowing that before landing. It could be ten minutes or more flying in that thermal before heading for the landing area, then another five minutes or more to get there, then a few more minutes for your landing approach and then landing. By then, that little bit of electric power the LVC was trying to reserve for the radio is likely to be long since all used up.

By using a separate radio battery, we avoid all of this. The radio battery powers only the radio, and its life is subject to the same rules that govern the radio battery in other models.

Don Stackhouse
DJ Aerotech