ORIGINAL: aeajr
ORIGINAL: MikeEast
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?
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.
You misread but thats ok I do it all the time, Here is what I said in the above post
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.
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..