Ok......am I missing something pretty basic here? I bought a radio and am messing with it, figuring it out......the computer tells me when my battery is low.....I'm assuming its reporting the TX power....how do you know when your RX battery is getting low......other than waiting for it to fall out of the sky. Do I just assume that the the TX batt is always more charged than the RX batt? Assuming they were both charged correctly...thanks for helping the new guy

dsk.. You have to check the onboard batteries, with an expanded
volt meter:
http://www2.towerhobbies.com/cgi-bin...?&I=LXNK81&P=0
Or you can have a battery checker mounted on your plane:
http://www2.towerhobbies.com/cgi-bin...?&I=LXMZ56&P=0

But you should check at least every third flight, sometimes sooner:-)
And no matter if you let your batteries charge over night... Before
the first flight.... Put a meter on and make sure.. Cheap insurance!!
I lost one plane because on a low battery... If I can help it... Never
again!!

I am new too. You need to test them every other tank or so, for a trainer, I think every tank may be too often, but it beats bagging your plane in pieces. Any good field charger will both be able to test your Rx battery and charge it in minutes if needed. There are on-board meters you can buy, but that seems a bit over-the-top for a trainer.

Your Tx battery may last longer than your Rx. It really depends on the pack you use. If you use NiCd you will need to cycle...I hate that idea so I went to NiMH and it seems to be OK.


Good Luck Man!!

Thanks for the question and answer , now i know too !

Hello Should I store my TX an RX batts charged or discharged?
Thanks, Mike

I put a Voltwatch batt monitor on all of my planes... just bang the servos around before and after each flight and see how low the meter drops... when it starts getting down in the low region, stop and recharge them. I also put an AirAlert on all of my planes too... makes recovery in the corn or brush much easier (we have both around our field). The AirAlert also has an audible low batt alert, but I use it mainly for recovery insurance... Voltwatch is a better monitor for your batt pack.

http://www2.towerhobbies.com/cgi-bin...&I=LXSZ87&P=ML

I've heard from several sources that NiMH batts should be stored with some charge, but I don't believe NiCds care either way. I always try to charge my batts up when I get back from the field, and then usually peak them (about a week later) just before I fly again.

pkh,
you want to store NiCads in a discharged state.......otherwise they develop a phenomenon known as 'memory' where they will only charge up to the capacity they were stored at...if they were stored at 95 % then they will charge 5% and maybe dischage 10% and be stone cold dead. Very very uncool and the epitaph of many proud aircraft over the years. Just my .02 worth.

Rich

"Memory" is a myth. When NiCDs first came out they were used primarily in lab conditions where they were discharged to the exact voltage level every time and they developed a "memory". If they were then tested, their voltage would drop off quickly after they reached that point, but our situation, and the technolgy of the cells is different today and it's simply not true. But like most myths, it doesn't die easily.

I generally leave my packs in whatever condition they were in when I left the field, then give them a good "overnight" charge before I go to fly (at least 14 hours or so). Or I use a Quick Peak charger to charge them on the way to the field. As long as you don't exceed 1C (1 times the rated mAH of the pack) you won't have any trouble. I have packs that are 4 to 5 years old and still test at 90% of their rated capacity.

Your transmitter pack will usually last at least 8 to 10 flights. The receiver packs usually won't get you more than 4 flights before the voltage is too low to fly safely. You should check the voltage with an ESV (like the one Raideron linked to) after the 3rd flight (minimum), and EVERY flight after that.

I won't fly if my pack gets down to 5.0 volts, but having a Quick Peak field charger lets me charge packs whenever I want, so I can fly all day. A pack discharged to 5.0 volts can be recharged with a Quick Peak charger in about 20 to 30 minutes at 1C.

You can pick up an inexpensive Quick Peak charger for around $35, then go to Radio Shack and buy a car "cigarrette" lighter adapter and charge directly off your car battery.

Later on, you can buy a couple of 6 cell RC car packs, wire them in series, and use them on your 12 volt airplane starter. You can charge that at the field too.

Have fun.
Dennis-

When you are counting the number of flights between testing batteries, don't forget the time that your radio was on in the pits while you were tweaking on the controls/trims and other stuff. It can add up in a hurry. And then there will be the times when you just plain forget and leave it on for some dumb reason, DOHHH!! Have'nt done that for at least a couple of weeks [&o]. Oh well.

Bruce

IMO the best bet is to check before every flight.

Apart from the fact that this makes it part of your fixed routine so that you don't forget, it can also catch "anomolies" rather than you just checking for regular discharge. As an example of what I mean - on my heli, I could normally get 3 flights on a single charge, but one day I tested the battery before the 1st flighgt and it was fine ; flew for 10 minutes, shut off & refueled, switched on and plugged the ESV in and found that under load the voltage fell off much more than expected. Turned out that one of the 4 cells had just crapped out and although there was still enough juice to make the servos move and give the appearnce of normalcy, the heli would not have survived another flight.

I agree with checking before every flight... cheap insurance, both for your planes well being and everyone's safety. If you put a VoltWatch on your plane, and have a computer radio with voltage readout, you'll always know the condition of your RX & TX batts. Personally I don't like the meters... I don't want to have to hook something up to check the batt voltage every time... easy to forget. The onboard batt monitor is always on and very convenient. If you cycle all your servos at the same time and watch the readout, you can see the loading effect without using a separate loaded batt meter.

I've heard arguments both ways on NiCd memory, and even NiMH memory, so I just do whatever is convenient for me, and occasionally cycle the packs with my charger/discharger to "condition" them. I don't really run NiCds anymore, mainly NiMH, and the general consensus I've seen for those is that they have little to no memory effect, and should be stored with some charge on them. Charging them when I get back keeps them charged up for the next time, in case I don't have time, or forget to re-peak them before my next field-trip.

Thanks for all the info.....looks like the onboard monitor is the way to go....very inexpensive

That's the approach that I take fo rall of my "big stuff" - e.g. all my jets and my giant scale stuff use on-board voltmeters from I4C products (http://www.i4cproducts.com/products1.htm); for my smaller, cheaper models I just plug in an ESV.

Another advantage to the onboard volt indicators is that if you have a servo going bad or sticking and draining too much current without you knowing it, you will get a low voltage indication telling you to check things out. Another idea is to use a charger that indicates how many milliamps charge a battery takes. For example, if you usually have to recharge 100 mA after a flight, and suddenly your having to recharge 300 mA, something is wrong, fix it to prevent crash. Or if you are using 500 mA per flight, and have only 600 mA battery, you better get a bigger battery!

I went back and read your original question. Assuming anything is leading to a crash. The transmitter battery voltage and indicator have nothing to do with the receiver battery. Transmitter batteries usually last longer because the are not powering servos. If you get a warning beep from the transmitter (indicating low battery of transmitter only) while you are flying, it usually means keep an eye on the plane because it will crash from lost signal because the transmitter battery is too low. There may not be enough time to land. Without onboard indicator, you have no clue about receiver battery charge. Just because you fly three times without a charge on receiver battery does not mean you will always be able to complete three flights. Batteries get weaker over time, maybe you left a switch on longer than you thought. Also the cheap, low power chargers need to be plugged in 24 hours to charge, time to full charge is only a guess, because they do not indicate milliamps. So you should not use these for fast charging at the field because they just don't have enough charging power. The safest thing to do is to take off with full fuel and full charge, until you get some sort of indicator. Another point, battery voltage is not very accurate indication of how much current the battery has. A partially discharged battery can have fairly high voltage, but remaining milliamps in battery can be very close to cut off point. You need to test voltage while drawing milliamps from battery. If all this is confusing, study up on basic electronics or ask experienced flyer.