|nigel newby||04/11/2018 17:12:15|
161 forum posts
Thanks for that Martin, Will try a few more discharge/charges but I have a new battery winging its way to me as we speak. I am now getting about 3 mins full throttle, although I do not know what it should do on a 2500, as my last battery was an 1800. This as I said would go up for a while then turn the motor off and glide till it required another boost. But I know other at the club who get 7-8 mins from a battery and that is belting around the sky, but I do no have a clue what their set up is. Must ask next time I'm there.
Pat Mc the first picky you showed is very much like mine, but my elevator is about 1/3 of the way up the rudder.
Mine is a seagull 2200, flies nice and gentle.
All the best to you all, and thanks a lot for all your help.
|Peter Christy||05/11/2018 16:50:14|
|1591 forum posts|
Apologies for coming to this thread late - I've been away from home, and incommunicado!
Nigel, one thing that *may* have happened is that the cells have become seriously unbalanced, ie: some cells are reaching a full charge while others are only partially charged. Your charger is detecting the "full" cells peaking, and switching off before *all* cells are fully charged.
Now, I don't normally recommend trickle charging, but its the only way I know to balance a welded NiMh or NiCad pack. Its probably a good idea to discharge the pack as far as you can, and then leave it on a 1/10thC trickle charge for 14 hours.
If your pack is 2500mAH, charge it at 250mA.
Yes, this will over-charge some cells, but at 1/10C, it won't do them any serious harm (as long as its not done repeatedly!). This should ensure that all cells will get a full charge. Once done, see how long it performs for under load. If you recover your previous flight times, you should be able to revert to peak-detect charging.
You may need to do this a few times to get everything back in balance, but its worth a shot.
Trickle charging every time is not a good idea, as it often leads to the cells being repeatedly overcharged, gassing and drying out the electrolyte. However, doing this a few times won't hurt.
You will need to get hold of a suitable, old-fashioned trickle charger, but someone in your club is bound to have one!
Best of Luck!
|nigel newby||05/11/2018 17:30:49|
161 forum posts
Hi Peter, thanks for your comments.
Have just done another run on the motor, and I am now up to 5 minutes run time. So things are looking much better than they were. I dare say another couple of discharge/charging sessions and all may well be ok. At least it is now usable.
The funny thing is that I have 4 multimeters, and they all read different voltages.
One shows nothing, another shows about 2.5 volts, and it is set to dc not ac. Another digital shows 7.8 volts, and my ever trusty post office meter shows 7.4 volts. That is are having just done a 5 minute run on the motor. So I dare say all cells are giving out a voltage as that battery should be 7.2 volts. So when we have some decent weather and I have some spare time I can go flying.
Not been lucky with batteries lately, having not only just bought new batteries for my radio gear, but also my camera, and a new battery for the car.
All the best Nigel
|Peter Christy||05/11/2018 18:17:27|
|1591 forum posts|
Ah, yes, the meter calibration problem! I have three or four LiPo checkers, and they all give different answers! But one agrees with my charger, so I assume that that is more or less correct!
I have the same problem with tyre pressure gauges for the car! Between my wife and I, we have four, and only two agree! The difference in the others is as much as 5psi!!!
I would still recommend a couple of 14 hour trickle charges, if you can beg, borrow or steal a suitable charger!
Please login to post a reply.
Want the latest issue of RCM&E? Use our magazine locator link to find your nearest stockist!