waiting between flights?

[skrez]

Hi guys,
Im flying a Alfa F-86 with Don`s wicked 4800kv and e-flite 40 amp esc, and Hyperion 3s 220035c lipos. My 1st flite at the field is blistering speed at about 3/4 trottle, I fly between 3/4 and full for short burst. After landing my esc. and battery are only luke warm. I put a freash battery in and fly a second flite. I notice that there is considerable less speed and I can hear that the motor and not at full rpm`s. . Is this normal? Should I wait 10 minutes between flites, is it possible the motor needs to cool off between flites?Thanks in advance.
Frank

[Flexserve]

yes and no..sounds like a battery was not balanced properly? Do you balance charge your batteries? I'm also NOT referring to the cheap chargers with no LCD readout.

Luke warm doesn't affect any of my flights on similar setups. When the heat gets to the point I would question holding onto an esc or battery with my bare hands..that's when to wait.

Also was the temp on the motor hot? (If you could get to it) A hot motor will also cause "lagging throttle" and turn your air rocket into a lead sled.

[skrez]

Thanks Flexserve,
Yes I do balance my lipo`s with every charge, I use the TP 205v balancer. As far as the motor being hot, I really can`t get to it. The motor was lagging like you decribed, I`ll try tommorrow with a freshly charged battery and see how the 1st flite goes. If the 1st flite is good, then it must be a hot motor. If the 1st flite is lagging rpm`s, then maybe the rotor is slipping on the fan?
Frank

[kelberts]

Keep overheating your motor, and it will demagnetize, and lose power, eventually all power.

[skrez]

Guys,
I flew today with the same results, 1st flight was lighting fast speed . I waited about 5 minutes and flew with the second pack to find that the motor was lagging rpm`s. On the second flight it had most rpm`s at 3/4 trottle and if I went full it would start to lag. In both cases the battery and esc. where luke warm. I did not start noticing this problem until I went to the higher C rated battery`s (35c). I`m using a E-flite 40 amp esc,. I`m wondering if the esc. is having troble maintaining higher rpm`s?? Maybe I should try changing to Don`s Pentium 40? What do you guys think?
Frank

[Reco]

Could be a poor performing battery. Do you start out with the same batt on your first flight? I take it both your batts are not identical is that correct?

[skrez]

Hi,
These are 2 brand new Hyperion 3s2200 35c lipo`s. I purchased them last week, I start with a fully charged and balanced battery with every flight.
Frank

[Reco]

Are you using the same batt for your first flight everytime?

[skrez]

To be honest I`m not sure. I will mark them #1 & #2 and then try swiching . Frank

[Reco]

It sounds like one batt is not the performer the other one is. I always and alot of guys do mark each batt especially when dealing with identical batts. Some even mark the number of charges per batt. I use a black sharpie. Mark them then fly each one. process of elimination should reveal your weak batt. If both batts fly good on the first flight with the motors cool then your getting too hot and may need to reduce flight time or stay off full throttle a little more.

[skrez]

Yes I`ll let you know how that goes with the batterys. Do you think it`s possible that the esc. cannot keep up with the higher rpm`s of the higher c batterys?
Frank

[kelberts]

C rating has nothing to do with RPM (Unless you're using such a small capacity battery that the voltage sags under load).

RPM increases with voltage (cell count).

You should put a meter on your system and see what's really going on in real time. Is the voltage sagging under load? Is the system drawing more power when hot?

My guess is either one battery is a little limp, or when your motor heats up, it loses power.

Don't think it's the ESC. ESCs work hardest at mid throttle settings, and WOT is actually easier for them, assuming you have one that is rated high enough to handle the amp draw.

BTW, have you checked for rubbing/binding in the fan? Maybe when it's been running, something is expanding and causing extra friction - That would make everything bog down a bit, converting the power to heat instead of thrust.

Also - check your wiring - a bad solder joint can heat up due to resistance, and that will also rob power.

[skrez]

thank you for your reply kelberts . Why is it when I used the higher c batterys it seemed like I had about 20% more power? Where is that power coming from? Maybe just a fresher battery?
Thanks ,
Frank

[Reco]

A higher c rating denotes a higher discharge rate (More Power). If your setup is capable of producing more power it will draw it out of the Batts as long as your ESC can handle the current. Foe instance lets say you have a 15C batt that has a 1500mah capacity. you would multiply 15 x 1500mah or 15 x 1.5 amps. That would give you a batt that can discharge 22.5 amps. A 20C would discharge a 30amps and so on.