is it safe to fly at any Tx voltage provided the low battery alarm hasn't gone off? for example fully charged my radio reads out 10.1 volts , and by the end of the flying session the voltage drops down to about 8.9 sometimes 8.8.


so is it safe to assume that flying at 10.1 volts is just as safe as flying at 8.8 volts, a few tenths of a volt right befor the alarm goes off?

the radio is a futaba t8uaps BTW

Safe? While you may have control at those voltages I wouldn't push it. The typical TX battery is 9.6v. Technically, anything under that and you should recharge. Most TX manuals will even tell you that the beeping for the low battery isn't the warning to recharge. You should have done that long before you hear that tone.

When you mean flying session, do you mean all day or just after one flight? If you're losing that much voltage after one flight you might need to either cycle the battery for the TX or get a new one. If you are losing that voltage through a whole day that is somewhat normal. If you're concerned you can always pull the battery and use a field tester with a load built in to test the battery. That will give you a good indication of it's output.

Hope this helps.

thanks, my typical flying session is about 4-5 10 minute flights, i replaced the 2 yr old cermark 1100 mah nicad battery with a new hydrimax 1650 nimh battery.... ..... could something be wrong with my Tx that the voltage drops rather rapidly? i just noticed this behavior over the pst month or so.. my brother thinks its too much of a coincidence for both sets of Tx batteries to go bad. could it be that something may be wrong with my transmitter?


thanks

ok i have a hobbico digital volt meter MKII an i set on tx with a load and it reads 10.14, ............ but the voltmeter on my tx reads 8.8..... it doesnt make sense

There could be something wrong. With winter approaching you could always send it in to Futaba to have them check it out. My TX has logged some 80 hrs on it since I bought it a year ago and I plan on sending mine it this winter for a checkup. It wouldn't be too uncommon for issues to arise from a jolt here and there. On an unrelated subject, a guy at my flying field sent his JR radio in and the techs found there was actually a piece missing from the circuit board! Not sure what it did but thankfully he didn't lose any planes.

NiMH batteries, while better than NiCd, still have some memory. Cycling them can fix that. Depending on your charging/discharging habits this could also be the problem. If you don't have a battery cycler and plan on staying in this hobby I would definitely get one! If you know someone who has one you might borrow it and try that.

That is weird, 10.14 on a loadtester and 8.8 on the TX. I would expect the results to be the opposite since the TX doesn't do load testing (at least I don't think it does). You might try posting this in the Futaba forum under radios. See if one of the reps can help you with that. I'd be interested to see what they have to say.

thanks for all you generous replies, perhaps ill post it tomorrow in the futaba forum, right now im off to bed

also winter where i live is the season i/we like flying best, winters down here in deeep south texas are very mild, ....the winter birds, AKA winter texans spend most of their winters down here just to get away from the cold, so now really isnt a good rime to send it off, but i guess if i have to i will.... again thanks

It needs to be recalibrated...

I did some searching through the Futaba forum and found this thread:

http://www.rcuniverse.com/forum/m_33...tm.htm#3324850

Nutshell version, you'll need to send it in....

What are you using to charge that higher capacity NiMH pack? If you're using the 50 mAh wall-wart that came with the Tx/Rx you probably have to leave it on a LOT longer, like 24 to 30 hours vs. 12 or 14 for the original pack.

I almost always fly my models until the Tx low battery alarm goes off. From experience I know that there is approximately 15 minutes of flying time left with my JR transmittere when the alarm sounds. I have never had an accident due to low Tx battery voltage, but I know some people want to be play it even safer than I do.

Futaba TX s show the load voltage. Example: CAP9 with the RF module taken out reads a voltage of about 11Volts on the screen, and If you put the RF module back in the TX the volts will drop down because of the load for signal transmission.

A *fully* charged 9.6Volt Nimh Pack should provide ~11.2Volts without load and ~10.8Volts with RF module load.
A *fully* charged 9.6Volt NiCd Pack should provide ~11.3Volts without load and ~10.9Volts with RF module load.

Ofcourse these are estimate #s but If your fully charged 9.6Volt pack shows anything lower than 9.6Volts on your TX screen, there must be something wrong with the pack. (unless theres a shortcircuit or current leakage in the tx circuit)

Im usin an ace charger, i dialed it in at about 200 mah, yesthe original 45-50 mah wouldnt cut it

thankyou for all your replies guys, i believe centenix found the solution


thanks

Back to the original questions, I wouldn't fly too far under 9.6v. As far as your radio is concerned, I would have it checked out. Given the other posts on here, we know the radio does load testing while on. How much load I don't know. But if it's reading 8.8 and you're Hobbico meter shows 10.14, that is a huge discrepancy. Both can't be right. I would err on the side of caution.

I would say you could just keep flying and check the battery manually. But even at 10v on the Hobbico tester, the TX will probably think the pack is so low it will just start beeping non-stop due to the low battery warning. If you have a flying buddy close by with another load tester you could doublecheck the results of the Hobbico meter.

When I get home tonight from work (3 am), I'll pull the battery from my 7C and run a load test on it, then see what the TX LCD says.

The modern Futaba TX s are designed to work (meaning there would be no change in signal quality and power) down to 8.4Volts.
However, any voltage reading below 9.6V is dangerous because it will fall below critical levels much faster than it took it to get down from 10.9V to 9.6Volts. (NICD and NIMH Discharge Characteristics)

It is a wise thing to keep the voltage reading above 9.6V on the TX screen.

i wont be flying this weekend, my alma mater's highschool football team made it to the playoffs and its a family decision i had to make so i guess i wont fly until next saturday, really the only day out of the week i can go flying.....


i checked my flight pack which i rarely do.....rated at 4.8 gave me 5.29 i just need to actually check with someone e lse's to cross reference......


thanks for the replies

ps i charged my tx battery for a while and my hobbico meter gave me10.61 and my tx read 9.3...... , i will send it off to futaba..... shouldn't cost more than 50 round trip...its wort it