How much time should i get out of my rx battery. I have a JR 700 RX with 6 servos on it. It seems to need a recharge after 2 flights. I used my instructors quick charger to keep it flying. I have been getting about 18 minutes of flight time today. The winds were a bit gusty but no more then 15 mph.

Seems kind of short, but 6 servos, especially if they're high torque, digitals, is more than the typical load. You should test your battery, but perhaps look into something with higher capacity too.

Once again I've got to agree with Piper_chuck. That does seem a bit short for battery life. Let's not worry about the battery for a minute. Things that can affect the life of battery can actually be mechanical problems with the plane. A binding of a control surface can cause the servos to have to draw more power to push/pull that control surface. A servo that is going bad can draw more power than normal and drain your batteries. While not very common these things can cause problems with your battery and shorten your flying time. More than likely you have a bad battery. It's possible that this radio sat on the shelf for awhile before you got it and the battery is old. The best thing you can do is see if you can find somebody that has a battery cycler. This will drain the battery and measure how much time it takes to drain. This will represent how much flying time you will have out of that battery. If it matches the time you are getting in the air then your problems are with that battery pack and it's time to get a new battery. When you buy a new battery one with a higher capacity and I would recommend getting a NiMH pack instead of a Ni-Cad battery. I have 1600 MaH NiMH batteries in my 40-60 size planes and I can usually get 50-75 minutes of flying time out of them each time out to the field.

Hope this helps

Ken

I have noticed that some times the flap servo buzzes, but if i turn my tx of and turn it back on and not use the flap servo it doesnt buzz, but there is no way to tell what it is doing in the sky. I have thought about returning to the hanger 9 default setup and not use the flap servo at all. My instructor doesnt like the idea of using flaps to land and take off.

If that servo is buzzing it's entirely possible that it's binding and drawing more current. Try taking that servo out, or unplugging it, and see what it does for you flight times. That could very well be the cause of your problem.

Ken

You say "It seems to need a recharge after 2 flights". On what basis are you making this statement? You should be checking the battery pack with a loaded voltmeter. If it reads 4.4 volts (for a 4-cell pack) then you are definitley done flying until you recharge. If the loaded voltmeter reads 4.8 volts, then the pack could still have a lot of energy left in it. As RCKen said, you need to check the battery with a cycler. The general procedure is like this: Charge fully and fly perhaps two timed flights. put the pack on a cycler to measure how much was left. with this information, you know how much longer you can fly the next time.

at the end of the second flight the meter showed 4.79 volt. I have a V-300 voltmeter and we checked it against another volt meter and the reading were very close. I have the standard 4 cell pack in my plane. I am very paranoid about running out of battery in the plane.

With the pack reading 4.79 volts under a 300 mA load, you probably have only used up one fourth of your battery. Most 4-cell packs drop from about 5.2 to 4.8 in the first 10 minutes of use. Then they stay at 4.8 for 90 minutes, then they begin to drop again. See attached graph. You can try this: Fly two flights. Go home and sit in front of the TV and fly the plane (move the sticks around) for another 20 minutes. Then measure the voltage. I'd bet it is still at 4.8 volts. Then do another 20 minutes. etc.

Ok, first things first. Go to [link=http://www.rcbatteryclinic.com]RC Battery Clinic[/link]. It's probably THE resource on the internet to learn about batteries that we use in our RC planes. It should clear up all of your questions.

But for a quick answer of your question. If your battery is reading 4.79 volts then you probably still have plenty of flying time. I borrowed the diagram below from the RC Battery Clinic for a quick explanation of this. Ni cad batteries do not have a linear discharge rate meaning that the battery discharges at a constant rate as you use it. Looking at the diagram you can see that the battery will discharge to a certain level (approximately 4.8v) and then plateau at that voltage for a period of time before continuing to drop voltage. How long will it stay at that level? That depends on usage, battery state, temperature, and about a dozen other factors. This is where a battery cycler comes in real handy for finding out how much time a battery has left in it. You can do a "poor man's cycler" by taking your plane into your living room, make sure you have a full charge on the battery. Start moving all of the servos like they would if you were flying and time how long it takes your battery to discharge. Check your voltage levels as you go along. This will give you an idea of how long you can safely fly, which should give you a little piece of mind. You should be able to fly safely until your batteries drop to a level of 4.4-4.6 volts. When it gets down to that level it's time to pack it up for the day.

Hope this helps

Ken