When do you quit flying?
 

I have been flying for years and have never heard a good answer as to when to quit flying due to low battery in the transmitter. I just finished cycling the tx pack from my Futaba 9C because it seemed like it just wasn't lasting as long as it used to. I generally quit flying at 9.6volts or thereabouts. Looking over the graph on my PC from my cycled pack, I noticed that the pack dropped to 9.6 volts after only 76 minutes. It was able to maintain over 8.8 volts for another 2 hours and 20 minutes. This was at a load of 250mah. According to my manual, the tx draws 280mah. The pack finally "dumped" when it reached 8.5v and the cycler cut off after just a few minutes.
So, is the transmitter safe to fly as far as RF output down to 8.8 volts? I have never ran my 9C down that low so maybe it has a low voltage alarm I haven't reached yet. I want a real technical answer not rule of thumb or this is what I do type deal.
After 4 cycles, the pack will maintain 9.6 or higher for 102 minutes now. I do a bit of fast charging at the field when the voltage drops so I'm sure that hasn't helped the pack life.
If you are curious, I was using an Orbit Microlader Pro for cycling.
Thanks,,,basmntdweller

When do you quit flying?
 

I generally quit flying with my TX before 9.5. THough on the 9C tx it doesn't start beeping at you till 8.5. To me that sortof dumb. What's the point? If it's at 8.5 you've already lost your airplane so......

When do you quit flying?
 

That is the kind of info I want! If it doesn't start warning till 8.5, wouldn't it make sense that it is still safe to fly? I'm not positive, but I don't think RF output is related to voltage until it gets real low like 8.5. I may be wrong but the RF output is modulated(terminology???) irrespective of voltage until it is too low to safely control the model hence the warning buzzer at 8.5volts. I probably should have put this in the Futaba forum to get a direct answer from GP/Futaba.
basmntdweller

When do you quit flying?
 

FWIW - Battery manufacturers state the cell's capacity based upon discharge to 0.9V.

On an 8-cell Tx pack, that would be 7.2V. THEORETICALLY, it might be safe up until then. I on the other hand, will stop when I reach 1.1V per cell to provide a safety margin (and many experts agree at this cut-off). This means, with an 8-cell Tx pack, I'll stop when it reaches 8.8V.

I keep stating voltage on a per-cell basis, because I'v heard of some Tx's using 6-cell packs.

When do you quit flying?
 

That is kind of my feeling too. I don't know that RF output is safe down that low. I think it would be but I don't want to risk a plane to test it!
basmntdweller

I posted a reference to this post in the Futaba forum. Hopefully, I'll get an informed answer on the subject.

When do you quit flying?
 

I agree it's kind of stupid to keep flying until your battery hits 8.5v, but I did that once, unintentionally. My transmitter started beeping and I landed my airplane right away because I thought there might have been some kind of electronic or programming problem with my transmitter.

I realized after I landed that I totally forgot to recharge my transmitter since my last flying session when I saw that the meter read 8.5v.

I know from first hand experience that your transmitter keeps working until it beeps from a low battery condition, but, I don't recommend pushing it.

- Francis

When do you quit flying?
 

I've run my 9C down to 8.5 while flying my Pizza Box Flyer (you have no idea how addicting those can become) and was able to bring it in safely. I did fly a Zagi using a 9Z where the voltage alarm went off for a good minute before the plane lost control. I put my 9C back on the charger when it gets down to 9.2 or so.

When do you quit flying?
 

The Futaba 6X beeps at 9.5 and shuts off at 9.4. A friend found that one out the hard way :(

HiTEc Eclipse beeps at 9.3 and shuts off at 9.2.

I like the 9C. Doesn't shut off untill it literealy doesn't have the output to function. I was dinking with it once. You couldn't read the screen. I hit mode and it took about 15 seconds to get into the programming. And it didn't go beep-beep it went beep..........beep :D

Just to be on the safe side, I'll stop near 9.5. Not worth my airplane on a "theoretically".

When do you quit flying?
 

Man, those are conservative cut-off's. Is there any way to change them? My Tracker II alarm beeps somewhere around 9.19V, and I think it can be changed from within the service menu. I don't know when it turns off. I don't know the exact alarm voltage, since it only happened once on the workbench, when the alarm informed me I had forgotten to turn it off.

Field Charging
 

By the time my Tx hits under 10.2 volts, my plane definately needs to be charged, so I simply field charge them both. Works for me.....

When do you quit flying?
 

When you refuel your aircraft why not refuel your batteries to.
Darryl Usher

When do you quit flying?
 

I've never had the alarm go off while flying, and all my previous radios didn't have alarms, so I decided to run a test to find out the truth. Here are my results:

The alarm on the Tracker II started sounding as soon as the voltage dropped to 9.19V, and the RF meter didn't start dropping until the voltage dropped below 9.0V. I was still getting decent range checks around 8.8V, and the radio stays on until it doesn't have enough juice to power up (6.69V).

For more clarification - when I stated earlier that I stop when they reach 8.8V, I was reffering to my old analog radios which didn't have integrated volt meters and alarms. I guess I won't be running it that low anymore.

When do you quit flying?
 

On a RX pack, if it shows 4.7V under load, I do one more flight. ( except with big planes with lots of high current draw servos )

On a Tx, same thing... if it shows 9.4V under load, I do one more flight...

When do you quit flying?
 

There is no single correct answer to this question. You need to cycle your pack at the end of the day to determine how much capacity is left, then adjust your stop flying voltage accordingly.

Different packs have different internal resistances. Different radios have different metering circuitry. You need to deterine what is right for your particular situation.

When do you quit flying?
 

True...

When do you quit flying?
 

In the manual for my new Futaba 6EXA it has the following "recommendations"

9.4 - No more flying till recharge
8.9 - Land soon
8.5 - Emergency

At 8.5 I beleive the transmitter turns off as well after beeping (at least it did when I first got it and the batteries were near dead).

I usually stop at 9.8 - that usually gets me enough flights for a half day of flying and if I want to fly more I recharge with my field charger or more likely I quit flying after a full morning or afternoon of it.

When do you quit flying?
 

I'm gonna build myself a nice 2100mAh pack for my 9C. I won't have to recharge 'till next year :D

When do you quit flying?
 

This is the Correct Answer!

I've got 1600 mAh NIMH packs in both of my power-hungry 10X radios. I haven't needed to recharge in the field since I swapped them in.

When do you quit flying?
 

I always run out of planes before I run out of voltage in the batteries... is that a bad thing?

When do you quit flying?
 

Only if you hate fixing / building. :D :p

Next outing, see if you can run out of both on the same flight...

When do you quit flying?
 

Or bring another TX pack.

Or bring 2 TX's.

When do you quit flying?
 

a new battery is cheaper then a new TX. Especially when you're looking at $300+ transmitters

When do you quit flying?
 

True. But if you already have 2 TX's (same model) then you have 2 batts. :)