Been going over the book again and i noticed it says check the battery voltage on both the tx and rx.Don't fly below 9.0 volts on the tx or below 4.7 volts on the rx.The tx has 9.6 volts charged and the rx says 4.8V charged,would this sound normal ?.I don't want to fly with dead batteries but to me it sure dont sound like a very good setup especially with just .1 volt drop.Maybe a misprint but i sure dont want to find out the hard way.
Thanks

This don't sound right as a fully charged rx battery should read in axcess of 5 volts, perhaps as much as 5.3 which would give you a much larger window which will stay mostly within that range for the life of the charge. As the running time available gets close to the end the voltage will be at or close to the 4.7 or 4.8 readings which is the time to charge This will be about 2 hours of flying time on a 600 mill battery with the radio drawing a nominal 250 to 300 mill load.
This is however the outside parimeter of operation so you shouldn't run it down that low. It is in my opinion cutting it a little too close.

Your book would be correct. The Tx will be somewhere around 10.6 volts when fully charged and the receiver battery will be around 5.3v. Flight time on a full charge will depend on your style of flying. A lot of aerobatic maneuvers will deplete the airborne battery faster than just flying around in circles. Never rely on just flight time alone. Check the Rx battery before every flight with a good expanded scale voltmeter and stop flying when the voltage gets to 4.8

Your voltage readings are too low. Don't know what you're using to check them, but if it's not an expanded Scale Voltmeter, get one.

A freshly charged receiver pack will often show as high as 5.5, but 5.3 is good. I never fly below 4.8 volts. The transmitter fresh off the charger should read about 11.0, but will drop to 10.9 or 10.8 very quickly (within a minute or so). Again, at about 10 volts, I start thinking "charge it".

Although two hours of "on" time with a 600 mAH receiver pack is theoretically possible, check the pack with the voltmeter after the second flight, and after every flight from then on. It's not worth losing a plane because you "thought" there should be plenty of charge left. [&o]
Dennis-

The TX being down to 9.0 would be asking to crash. The drop from 9.5 to 9.0 (and below is very fast. Do not take off if the battery reads 9.6 or below on the TX. (I tend to quit before it reads 10.0...)

I also don't take off if my RX pack is below 4.9 v.

I may be a bit on the conservative side with the votages... but I don't lose planes to dead batteries.

**********

The time you can get with any given mah rating pack is dependant on too many factors to say you can depend on timing to say you are safe.

Depending on how I fly one model... I can get anywhere from one 20 min flight to four 30 min flights from one charge of a 700 mah pack. (obviously I moved to 1800 mah packs for that model to ensure I'd be safe for at least 2 flights.)

The average TX is gong to be able to operate 2 hours on a 700 mah pack. It is uncommon for the TX to run out of power before the RX. (unless the guy forgot to charge the TX...[&:])

Hope you guys don't mind but I thought I'd throw my little question in here.

My new JR X-378 says that the TX battery is a 600Mah pack. Therefore if the manual said the current drain is 200mah would the pack last for 3 hours?

Thanks

Zimbo

NOOOO

dont count on it....im a newbie but i have a feeling actually its the truth

if you run a tx for 3 hours and its only an 600maH battery your introuble
FElix

Youcan get UP TO 3 hours out of the 600 mah pack with 200 ma current drain. You should be recharging at close to 1.5 to 2 hours if you want to be safe.

It is always better to recharge early than to find out you have no power left in the TX or RX with the airplane in the air. The last model I saw that crashed from dead battery had no salvageable piece larger than a clevice.

Thanks FHuber,

If I haven't used the radio for a while but its still around 10v should I still give it a full charge?
Thanks
Zimbo

P.s- what about fast charging?

Anytime I have left the radio sit for a few days to a week I charge everthing overnite the nite before I intend to fly even when it's not been flown since the last charge. The self discharge will slowly deplete the pack and since it's not really measurable the safe way is to charge before you fly, it won't hurt it.

I got this data out of the book,something i didn't read before but i was glad i was glancing thru the book again but i have a question,Since i have the 4.8 rx battery pack,couldn't i get a bigger one and hold the charge better ?,same question for the quattro tx.
Thanks

Don't confuse the "rated voltage" of an airborne back (4.8v for a common 4-cell pack) with the actual measured voltage. As mentioned, 5.3v is pretty normal for a 4.8v "rated" pack at full charge.

If you fully charge your RX pack, and it only reads 4.8v on a loaded voltmeter, you've got a problem.

You can get a larger capacity pack if you wanted to. But with proper charging, 600mah on a trainer is usually plenty.

Also, the "wall wart" charger that came with your system, it's designed for a 600mah pack. If you go buy an 1800mah pack, it won't charge it properly. It would take at least 30 hours to charge, maybe more. It might not even fully charge it ever, since the losses in the pack might totally consume the low charge current that was meant for a 600mah pack. So, you'd need a new charger for a larger pack.

So, I suggest you not worry about exotic or extra batteries, and concentrate on getting your 600mah packs charged correctly.

However, going to a 6v RX pack will not help matters. In fact, a 600mah 6v pack will actually drain FASTER and give LESS flight time than a 4.8v pack of 600mah. The reason for this is that at 6v, the servos draw more current. It's Ohm's law v=ir in action.

I agre with rctrax, I try to toss my stuff on charge the night before flying, regardless of how much charge I think it might have. (note, "night before" does not equal midnight, when you're getting up at 7:30am for an early flight. That 7.5hrs of charge time isn't going to cut it. Get it on charge at dinner time.)

However, leaving your batteries on charge all the time on the come-with charger is not good for them, it will over-charge the packs.

Thanks for the info,i need to find myself a better meter.
Thanks

The key to using a meter with Nicads is to have one with a "load" on it. I strongly suggest you get a meter made by one of the hobby companies. A typical voltmeter from radioshack or whereever won't tell you what is really going on.

When people refer to "ESV"s, that's what they mean, though it's kind of a misnomer. (ESV stands for "expanded scale voltmeter". Having an "expanded scale" does not actually imply having a load on the circuit. I personally use a DVM (digital volt meter) that has a built in load (made by a hobby company). So it's not a ESV, since it has no "expanded scale", but it does have the load, so it works well. (and it doesn't break everytime I drop it like the cheap ESV's I had before)

This is because of the way Nicads work, they will show lots of voltage with out a load, then fall off dramatically with even a small load on them. Obviously, is the voltage under load we care about.

You can actually take a normal voltmeter from radio shack or wherever, and make up a test lead that has a resister built in to it correctly to apply the proper load. I did this for years, and the results are just as good, and more accurate (if you use a high quality meter) that the hobby meters. It's easier and cheaper these days to just get a meter made for this though.

Don't any of you fully drain the battery before charging it?
I thought that not fully draining it before charging will eventually lead to memory issue with the battery, meaning that it will hold less charge (mah).
I use my computerized charger to fully drain the battery before charging it.
Ideally for the Rx and Tx I use a low discharge setting, then for charging I use the slow wall charger over night.
What are your views on this? Should I do the discharge every once in a while?

I cycle the batteries every month or two, but not with every charge. (Transmitter too)

Gryphon,
Battery memeory like you are describing is no longer a problem with modern Nicads. Nicads have improved quite a lot over the last 10 years, and the memory thing is long history. So you don't ever need to cycle or fully discharge the packs to prevent memory.

You should cycle once in a while to make sure the packs still deliver full capacity. Not because of memory, just because they DO wear out, and sometimes you get a bad cell that just dies sooner than it should. (think about it, they make millions of cells, once in a while a bad one WILL come off the production line).

When you do discharge, you want to do it as you describe, with a quality discharger, at a reasonable rate. Dischargine a pack to 0 can be bad, because one cell might read 0 before the others, then get reversed as the stronger cells continue to discharge. This is really bad for the batteries. (discharging an individual cell to 0 won't hurt it. And a well matched pack of cells that all discharge exactly the same can be run down to 0, but as with any mass-produced item, the cells do vary a little in actual capacity, so the odds of getting 1 weaker cell in a pack, and haveing it reverse is non-zero).