Any ideas on how long the battery packs inside the planes last, in say, terms of gas. Like 3 tanks, yadda yadda....

I have a .40 OS Superstar trainer. And I have no idea how to tell how much battery life is left after a full charge

Usually the standard battery pack will last for three or four flights of about 15 minutes each. That is, assuming it was fully charged (around 15 hours).

It is a very, very, VERY good idea to get yourself a battery tester so that you can check your batteries after a couple flights. You need to be sure that your batteries are OK before you take your plane up, because if they fail in flight the plane will go wherever it was last pointed! I had one of my student's planes go into the ground last summer because of a bad battery pack.

I use a digital voltmeter from Hobbico. There are several brands and they all work well. Ask at your local hobby shop or the field where you fly. Cheap insurance.

Yeah I was looking into getting one of those, my roomate has one on his helicopter and it seems like something everyone should have. I guess I just need to break down and buy one.

Thanks for the info tho. I'll try to stick to about 3 flights then.

I have an LED indicator which monitors the Rx battery, a 1700mAHr Ni-Cad. This is installed in a .40 trainer with 4 Futaba 9201 servos (a bit of overkill, but left over from my old heli).

It has 5 green LEDS and 4 red LEDS. After seven 15 minute flights the LED indicator had moved from the 5 LED to the 4 LED. I discharged the Rx battery through my charger/cycler and found I still had approx. 1200mAHr left in the Rx battery.

Therefore I should get about 6 hours from the battery!!!! However I am only doing circuits and the servos are not being moved constantly. Most of the time they are probably stationary.

I do know with my heli, that an 1100mAHr Rx pack will only last for four 15 minute flights. But that does have five 9201 servos and a gyro. With a heli you are constantly moving all the servos, hence the vast difference in current draw and time.

The amount of time will obviously depend on the battery size, but also the type, and number, of servos used and the type of flying you are doing. You will need to monitor the battery to get a feel for how long they will last.

Hope this is useful.

Sarah

I'm no expert on batteries, but nicad batteries hold their voltage, then drop off at the end of their charge, so I have a hard time putting too much trust into a loaded volt meter... although I do use one, it could catch it, but it's not guarantee.

I bought a charger that will discharge also, so I can measure the max capacity of a battery when drained from a full charge, then measure the remaining charge left after a known number of flights, then have a guess at mah / flight.

When using a voltmeter that puts a load on the battery, what I do is to stop flying when the voltage under load shows 4.9 volts. You could cut it closer by flying till you hit 4.8 volts.

However, the problem here is that once you get down to 4.8 volts, you will run along for some period of time, then when the voltage starts dropping, it looks like a "knee". Drops like a rock and you can really lose control quickly. And if you are flying and it registers 4.8 volts after a flight, you don't know exactly how long it has been at that level.

I have invested in one of those field charger units that runs off the 12 volt battery in my flight box. It charges both the receiver and transmitter packs. This way I can spend a full day at the field without worrying about losing a plane due to a battery failure.

Hope that this helps,