RE: Fataba 9C Mods
 

Well i just talk to two diffrent Futaba radio techs, An both of them said there is nothing wrong with going below 9.6 to 8.4. They said the guys that only go to 9.6 are the guys with memorys in there ni-cds. So i guess i'm going to load the toy up an go fly an not min the volt reading ......thanks

RE: Fataba 9C Mods
 

masonman,
We have guys at my field that don't fly when there charge needle gets "OFF" of 100%.
To me it is personal preference. When people don't know you get very cautious.
No harm no foul. I understand batteries so I understand the relationship between capacity, load, and conductivity.
While I don't fly to 8.4 volts, I do fly to 8.8 volts. I do this because the end of the discharge curve is a lot steeper with NiMH than it is with NiCads. If you want to test it at your field then when you want to stop flying, leave your TX and RX on and set the TX to servo cycle. Then see what time it is and then go visit other members. You will see when the plane starts to act stupid. That is the end of your flying time.
I will say that 75% of the people who do this test will still stop at 9.6 volts. It can't be help when you don't know!

For me, I don't do full throttle snaps. I am afraid my wings will fly off. I see people doing them all the time. I don't because I am afraid!

RE: Fataba 9C Mods
 

Nope, original pack. I charge it up, return the timer to zero and go fly, come home turn transmitter on until it beeps due to low battery. Maybe it burns less power not moving the sticks? I do charge with the Hughes Charge+ so it gets a pretty good charge.

Not that it makes any difference but mine came with a 700mah battery.

RE: Fataba 9C Mods
 

Mine came with a 700 MAh pack too.

Manual says radio draws 280 MAh. Now maybe that is max and not continous. Perhap there is a peak and drop based on what you are doing. Based on 280 I would expect about 2-2.5 hours till low voltage signal.

For many people this is plenty.

I have been to glow fields, and those guys seem to take LONG breaks between flights. Over a 3 hour period some of them only take 3-410 minute flights. an agressive flyer may take two flighs an hours. Great generalization, I know, but this is what I have observed.

Electric flyers seem to land and swap packs, set one on the charger and go back up far more frequently. I see them more typically taking 2-4 10 minute flighs an hour. For them it better be a shorter day or get a bigger radio pack.

Thermal glider pilots seem to spend even more time in the air than either electric or wet fuel guys. Launch, hunt, fly or land and launch again.

I fly electrics and thermal gliders - the 700 MAh pack seemed to be OK for me but occasionally I had to recharge the radio at the field to get those last few flights in.

Slope glider pilots seem to get the highest air to ground time of any type of flyer I have seen. When I started flying slope I immediately went to 2000 MAh packs. When one of those failed I went to a 2500 that lasts forever!

So how long things last and what is enough is very much a personal thing and the type of flying you do.

RE: Fataba 9C Mods
 

Unless your system is putting out less power, you have a more efficient system that we do.
Good job in coming across it!

RE: Fataba 9C Mods
 

Well guys i went out today, An I'm glad to say the funtana is still together, I flew to 9.6 an landed an refueled an grabbed me a smoke an turned it into the wind.Gased on it an i was flyin. I was a little tense an watching every move the plane made looking for glitches. I just flew figure 8's about 60 or 80 feet up. Never seen a problem, about ten mins into it i set it up on final an brought it in fairly slow right over the stripe an pulled it up an fliped on the gyro an torque rolled for about 2 or 3 mins circled an landed an everything was working like it was when i first turned it on. I thank you guys for the input

RE: Fataba 9C Mods
 

OK,
I qualify as a beginner in this discussion. I can wire up a whole apartment complex from the ground up, but I just dont understand what i should about electricity in this line of thought.

Heres my recent experience. I fly a 9Z transmitter and I just put a 2000+ mah NiMH pack in it about 4 months ago. At first the pack would go for a week and never drop below 10 volts. Now, hot off the charger it is at 10.8-11v but within 10 minutes its down to 10v. After 2-3 flights its down to 9.6V and I chicken out and recharge. I do know that I use my 9C to fly on the sim and I have let it go down to 8.4 and actually had the Tx shutdown within seconds of getting the alarm. I digress on that, I am really more concerned about my flying with the 9Z.

So with that being said here I have a 2000+mah NiMH pack and I run it for say 50 minutes and I am down to 9.6V and back on the charger it goes. At the end of the charge it has received about 450-550 mah of juice. The other day I decided to cycle the battery and see what happened. On the 1st cycle it only put in 500 mah, on the 2nd cycle it removed and then put in 1000mah. Are you guys telling me that I should let my Tx go below 9V? Am I causing memory in a NiMH battery? Whats the minimum safe voltage? Is it normal for the battery to quickly drop to say 9.8V and then slowly fall off from there? I always have been told that 9.6V was about minimum from the old timers and just sortof took them at face value not really taking the time to learn this for myself which is actually a little out of character for me.

Teach me something here. :)

RE: Fataba 9C Mods
 

This has already been discussed extensively in the thread. You can fly at 9.6V and past that. Read the thread and all will be revealed to you.

RE: Fataba 9C Mods
 

I have read the thread Ed and all was not revealed.

I have been down to <9V and had my transmitter (9C) shutdown unexpectedly thank goodness it was while I was flying on the sim. That causes me concern about going below 9V basis peronal experience. I see Geist says 8.8V, I can probably live with that as I think the actual shutoff was at about 8.5V, I just am afraid of a sudden drop from 8.8 -shutoff before I can get my plane down. I drop 500-800 mah in the 1st couple of flights, that is what scares me. So if I am reading correctly the curves moves sharply at the beginning of discharge but then should decrease to a more level discharge rate from ~9.6V - ~8.8V. Point is can I expect more than the 30-40 minutes I get from 10.8-9.8V from 9.8V to 8.8V? That should be a lot of milliamp left after the 500 I lose from 10.8-9.8. I would hope there would be 1500++ from 9.8 to 8.8V of 8.4 is minimum. I reckon I just need to test it and see, but as Geist said about high speed snaps.. Im skeered.

The other issue is memory. Does NiMH have memory like NiCad? The supposed local experts say no, but I am not so sure about that especially since I cycled the battery and saw such a big increase in charge, discharge, charge after a few cycles... Any fact based comments on that?

RE: Fataba 9C Mods
 

Mike,
You have a different problem that is not related to your TX but your pack.
You need to cycle your NiMH pack 4-5 times with a good cycler to get your capacity back.
Then you can fly down to 8.8 volts with no fear. Here is my example.

I use a 2700maH NiMH pack on my ignition. After about 6 months, I noticed that my ignition would die while flying. I could only get 4 flight before the pack was dead. I would charge it and then go out and fly and only get 4 flights and it was dead again. I knew there was a problem so I cycled the pack. the capacity was something like this:
cycle 1 560maH
cycle 2 800maH
cycle 3 1200maH
cycle 4 1900maH
cycle 5 2300maH

For some reason, the pack would not take a charge until I cycled it.
Now I can fly 15-20 times and the pack is still charged.
What I am saying is if you continue to use a NiMH pack and never fully discharge it, you will loose capacity.
Now, you need to ask Red in the battery forum to find out why? I don't know the chemistry.
I do know that every 6 months, I cycle all of my NiMH packs to ensure that they retain their capacity.
I also NEVER use NiMH packs for the airplane electronics.

RE: Fataba 9C Mods
 

Thanks Geist. That helps. I did not know that NiMH was expected to have memory. Again I do not claim to know much about electrons and how they work so I took what I was taught about NiMH not having memory as gospel. Obviously that was incorrect. It sounds like a simple solution, cycle the pack until it comes back to capacity and then run it down to 8.8 before recharging to maintain capacity.

Now I run Lithium on everything inside of all of my IMAC 3D big stuff and I have read a LOT about them. All indications are that Lithium does not have memory and I am see no indications of memory in my Li Ions. Do you agree with that or have you had much experience with them.. I have been running 2400 7.4V packs and its a pretty constant take 800/day out flying recharge and put 800 back.. It takes about 20 flights to run them down to 7.4V but I have only tried it once and since I see no indications of memory indiced capacity loss, I dont worry about cycling Lithiums. Now I am curious.

I wish they would come out with a regulated lithium pack for the 9Z.

RE: Fataba 9C Mods
 

Mike,
I have had very limited experience with LiPo's.
I really can't speak to those.
I use NiCads in my 33% IMAC bird because of my experences with NiMH.
I will probably go with LiPo's one day.
When I do, expect lots of email from me! :D

RE: Fataba 9C Mods
 

Let's put some best practice discussions here. Typically I swap packs around 9.4V if I am about to start a flight but sailplane flights can be long and they can be at great distance and I ALWAYS have a spare pack so it is not an issue for me. But there is a a fair amount of time between when it hits 9.6 and when it hits 9.4. That is probably 30 minutes on the 700 MAh pack. If I was working a nice thermal and noticed I was at 9.4V I would not rush to land, I would continue to work the thermal. If it got down around 9V I would bring it in.

If your Futaba 9C shuts down at 9V you have a problem with the battery pack or the radio. The low alarm is 8.4. Now why would they have an 8.4 low alarm if it was supposed to shut down at 9V? Think about it. Does that make sense? Seem like something is wrong?

I have had my alarm go off at 8.4V and had time to bring a plane in from 1/4 mile out and 500 feet up and land it with no problem. That was on the standard 700 mah. On the 2500 MAh pack I can't recall ever hitting lot voltage alarm.

You should have several minutes once the alarm goes off. But if it goes off, land now! I would not make that the normal process, I just was not watching the voltage.

RE: Fataba 9C Mods
 

:)You misread but thats ok I do it all the time, Here is what I said in the above post
To praphrase, I was at <9v, I THINK about 8.5V when the Tx shutoff. But I see your point that I should have gotten an alarm before the Tx shut off. I may have and I just dont remember, its been a few months ago.

Big help guys, THANKS!


I appreciate the relative timeline of voltage decay that you represented, that gave me a better idea of how long a charge SHOULD last on my pack..

RE: Fataba 9C Mods
 

NiMH dont have memory, but they do need a c/10 formation charge and or 4 or 5 cycles initially before they come up to full capacity. Also other than the occasional discharge to verify capacity, NiMH batteries dont get any benefit from cycling, infact according to Red its not good for them.

Also, the voltage readout on your transmitter may or may not be the most accurate thing in the world though the ones I have seen that are off are usually off a consistent amount.

One other minor fact to add to the discussion, a synth module will add to the current draw of any transmitter its installed in so a 9c with a synth module will appear to have worse battery performance than another 9c with the same battery and a crystal based module.

Edited to fix technical typo

RE: Fataba 9C Mods
 

If they do not have memory then why do they start out with a very gently curve of decline from 108-9.8V when they are new but after a few charges they will sharply drop to 9.8V and then slowly discharge from there? Honest question, Im not being cute.

RE: Fataba 9C Mods
 

I'd never accuse you of being cute Mike!:D

I've paged Red to provide more indepth info before I stick my foot in my mouth.

RE: Fataba 9C Mods
 

[sm=50_50.gif][sm=wink_smile.gif]

RE: Fataba 9C Mods
 

I have heard that NiMH don't have memory.
Not really sure what memory is.
What I will say is that over time, NiMH will not have the same capacity as they had when put in first use.
This first use does include a formation charge and several cycles to bring the pack up to capacity.

RE: Fataba 9C Mods
 

Formation charge should be C/10 not 1C as BarracudaHockey stated (maybe he meant .1C which is the same as C/10). The differences in new discharge curve and those after some cycles is due to the state of the formation of the plates. If not given several C/10 charge/discharge cycles you will see what you saw until things settle out.

RE: Fataba 9C Mods
 

Sorry I meant c/10, typo.

Thanks Red.

RE: Fataba 9C Mods
 

Radio Shack Battery Holder and Energizer 2500mah NiMh rechargables is what I'm using in mine. I fly slope soaring and I went without charging it for a week and a half.

-Tomi

RE: Fataba 9C Mods
 

OK, so on a 2500mah NiMH pack the formation charge should be at 250mah/hr? So I would set my charger to charge/discharge at .25?

RE: Fataba 9C Mods
 

Formation charge will be 250ma for 14hrs to 16hrs.
Discharge should be at C/5 usually.
This will be 500ma and should last for about 5 hours before dropping to 0.9 volts per cell.

RE: Fataba 9C Mods
 

I would not recommend a peak charger for the formation charge. Use the wall wart. Even on the big packs, just do hte numbers.

Red may disagree but I have seen that 1/10 fromation charge is a "fastest" recommended number. I have had very good luck doing formation charges at lower rates for longer periods. I formed a set of 1100 MAh NiMh cells at 50 MAH for 30 hours, discharge to .9V/cell, then another 30 hours. Those packs are working very nicely and take a full charge on the peak charger at 200 MAh charge rate on my Triton.