rc4flying

My Feedback: (21)

Hello Guys,

I am new to jets and I have just started to run my new Jet Cat 140RX. The battery that came with it for the ECU is a 2100maH 3 cell LiFePo battery with 9.9v on the label.
Question is, how many flight of 10 minutes plus startups and cool down time, can I expect out of a battery of this size? Or should I ask, what would be a no-fly voltage ? The full charge voltage appears to be 10.2v if I am reading the charger right. I ask because I am totally new to this battery chemistry. I did fly one flight with a fully charged battery for a 10 min flight and recharged the battery. It appears to have taken 700ma. Would this sound about right ? Iuse up the batteries. do have a bigger battery comin, but would like to understand how these ECU's

Thanks for the help.

Thud_Driver

My Feedback: (1)

Somewhere around 6.9v, + or -, the ECU declares the battery dead (Power Fail) and shuts off.  It doesn't much care whether you're in the air or not.

Keep in mind, kero start takes a lot of amps and a battery which can put it out.  So your number is probably ok.  What you have to do is develop a track record of what you put back in, per flight, based on your normal routine.  What's normal for you and your particular jet may not be normal for us.   Over time, you will get to know what your average consumption is per flight.  You should also decide how much margin you want in the battery and recharge when you get to that level.  Volts are good to monitor but I prefer to know how much "fuel" is likely to be left in the battery too.

Right now, I'd suggest a max of two flights per charge on that battery and see how that goes.  I usually shoot for batteries that will give me 6+ flights per charge.

miniman

I am new to jets, and we started to get failed starts even though all seemed to be working well, it would start when the battery was freshly charged then refuse to start. To make the instalation clean and tidy I had put a 20 amp switch in the ECU power line. I replaced the switch and its associated cable with some 30amp cable and connectors and the problem was solved. This was a silly fault that had some very experianced jet fliers stumped.

So when you are working out how many flights you can get from the battery packs you are using, consider what voltage drop you may be getting from the install.

We are using a 3500 mah 2cell LiPo and the motor takes about 6-700mah per flight, of that figure 500mah is just from the start up the ECU uses very little once the motor is running.

Peter

rc4flying

My Feedback: (21)

Well, I have been taking the advice and monitor my ECU batteries during recharges. On my LiFe 9.9 2100mAh pack, I have been getting 3 solid flights. I now also have a 3800mAh 9.9v LiFe and I have gotten 7 good flights out of it. Just to note, I have been using a small blower to help during the cool down cycles. I plan to keep monitoring the usage and charging cycles of the batteries to learn more. As I too prefer to have the plane setup to be able to get a full day of flying with having to recharge.

Thanks for the info guys.
I look forward to learn more as I progress with my new jet.