I can I be sure my batteries will hold up. After charging , should I leave them turned on to see how long they will last. How long should an average receiver battery last during normal flying. I obtained some batteries and I want to make sure that they will hold a charge. Thanks

more info please...
is this an electric powered airplane which uses a single battery to power the motor, receiver and servo's?
what type battery? (NiCad/ Nimh or Lipo / LIFE?)
in either case it is a good idea, but typically the best way to check them is with a cycling charger (for Nicad/nimh)
in the case of Lipo's LIFE's, most good chargers have a similar function.

Nicad / nimh batteries have considerably different handling requirements than do Lipo/ LIFE's

No it is a glow engine. The batteries are standard JR flight pack batteries. They are 4 cell 650 mah . I have a simple trickle charger that charges both transmitter and receiver. Could I just simply turn it on and work the controls until I see it getting weak . I want to make sure my batteries are good before a test flight by a club instructor. How long should the charge last for normal flying.

Simple battery testers that will plug right in to your charging port and measure battery voltage both loaded and unloaded are available from most hobby suppliers. Unloaded means the meter is checking the battery's voltage with no load on it. Loaded means a switch on the meter enables a circuuit that draws roughly the same amperage as a couple servos. If the loaded reading drops below 4.8 volts, (6 volts depending on your setup) don't fly it. The voltage will be seen in a digital read out and these meters cost about $20.00. Or simply put a volt watch on the side of the plane. A volt watch is a small electronic device with a series of LED lights on it. There will be about seven or so lights. When the battery has enough current in it to fly a plane, the green lights at one end of the volt watch will be on. As the battary loses voltage, the yellow lights in the center of the volt watch will come on. As the battery comes closer to not being able to fly a plane, red lights at the opposite end of the green lights will come on. If you have red lights on, don't fly the plane. Volt watches do no show actual voltage in numbers, but it is a rough indication of whether or not to fly. These things are plugged into an open port on the receiver and are active any time the plane's on/off switch is in th "on" position. I noticed recently that these things had increased to about $12.00 to $15.00 each, but they can be found on the internet for much less.

Sorry, forgot about the last part of your question. As to how long to charge a battery is concerned, you are using a 650mah battery. Your charger is putting out 50 to 100 mah (it will tell you on the front of it. So, if it is putting out 50man, devide 650 (your battery's capacity) by 50 (the output of your charger) and you have 13. So charge for 13 hours. This is assuming your battery is dead right from the start. That probably isn't the case, so it's anybody's guess as to how long to charge. Most of us charge for five or six hours and then check with one of the meters mentioned in my first response. A 4.8 volt battery, unloaded, should show approximately 5.5 volts unloaded and drop to 5.25 volts loaded or there about. As said before, if it is below 4.8, don't fly.

A trainer, if the servos and linkages are all set up properly, should use around 70-80mah per flight. So you should be able to get 5 flights out of it before needing to charge. But do understand that caveat of everything being setup and working correctly. A failing servo or a binding linkage can easily double that current usage, so there's no substitute for checking your battery voltage between flights and doing a cycle test after maybe 3 flights to see what your actual usage is. BTW, using a smart charger and reading the mah that the screen says is not a reliable indicator. There is always some efficiency loss when charging, so that number will only be a rough approximation. Discharging the battery down will give you a good number to work with. Subtract that from the discharge test you did before installing the battery to calculate an average current use per flight. My rule of thumb is to go to half of the pack's capacity. That leaves a decent safety margin in case you miscount or do start having a servo issue.

That's good info Jester. Which charger would you recommend for the batteries. I just have the trickle charger that came with the radio.

Any peak detecting computerized charger with a display screen will work. The Imax B6 is a cheap one that will work fine. It's sold under several different brands for about $30. If you plane to use high performance lipos soon, I'd spring for something better like a Hyperion or Electrifly Triton EQ. Just make sure you are getting a charger that can cycle/discharge batteries since that is the only trustworthy test of a battery's reliability and your current use. I once bought a new Spektrum branded 4 cell pack from the hobby shop and found in the cycle test that it only delivered 20% of its rated capacity. It looked fine in the voltage test, and I would have flown with it otherwise. Having a charger that could do a discharge test saved me an airplane.