Just had a close call. I went out to fly my Giant Stik with the converted BME twin cylinder engine. I had recently cycled and checked the battery, and it had been on charge all night at the C/10 (overnight) rate. The cycle test had shown that the battery was good. This was using a good charger; the Accu-cycle Elite.

I don't know what happened, but when I got to the field and went to start the engine, the controls wouldn't respond. The battery was nearly dead, even after having been charged overnight. Like my flying buddy said; "It's a good thing it happened that way." "If it had just had enough juice to get you in the air and THEN died, you would have lost the plane!" And he is right. Close call....

So, be careful with those batteries!

AV8TOR

I live in fear of this or a loose connection and check voltage before every flight

Did you loose a cell?

How old was the battery pack?

Well, it looks that way. I plugged the pack into the charger and it shut off after about 10 minutes. Then I put my loaded voltage tester on the pack and you could watch the voltage rapidly go down until the pack was dead in about one minute. I pulled the pack apart, and all but one of the five cells test at 1.1 volt. The last cell checked at .9 volts and I threw that one away. I am going to re-assemble the pack as a four cell pack, and see if the cells work. Maybe I can then use it for a smoke pump or some other non critical application. It is really kind of weird how this pack failed. It was a Hobbico pack with Sanyo cells by the way, and it was possibly two years old.

Speaking of losing planes, or almost losing them, I was once flying my kit bashed low wing Stik. (The one in my avatar.) I landed the airplane, and as it was sitting there on the runway with the engine still running, I thought, "I'm going to take off one more time and fly for a bit." When I went to give it throttle to take off, nothing happened. I figured the throttle linkage had come undone, but then I noticed that none of the controls worked. I later found a minute amount of corrosion in the battery connector. Another CLOSE call....

Another note: My brother recently bought some unbranded battery packs off e-bay, (against my advice). He lost one plane with one of the packs. He gave me another one of the packs and I tested it. A brand new 2000 mah pack tested at 300 mah capacity, even after cycling, overnight charging, etc. They were junk packs....

AV8TOR

This is why I use a batt. back up system. There are many on the market, I paided $20 for mine.

AV8T0R I would not even rebuild the pack. Get a HydiMax utra cell 4.8 1200 ma. They are a top notch pack using Genuine panasonic cells. Or any other hi quality pack. That twin engine or any favorite engine & airplane is a heartbreak when lost by a battery. Capt,n PS Guys... post what new flight Packs you like!

Well, if I rebuild the pack, I certainly wouldn't use it on anything flight critical. Maybe in a smoke system, or maybe just a pack to have on the work bench to test radios, set up servos/controls, things like that.

I am still curious as to why it failed in the manner it did. Sanyo batteries are supposedly some of the best....

AV8TOR

Cell failure always is possible.
Reviving cells:
High current burning often burns away the internal christal spikes that grow in time and cause cells to short cirquit and fail. I use a 24V transformator for that. Just hook up the pack for a second or so. The high alternating current works miracles and restores the good cells, or kills the bad ones.
Recharge, and measure current drain afterwards.
BTW, I always measure how much charge my cells take. If the charge is low, I discharge to check total capacity. If this is low, even after "reviving" as described above, cells need to be discarded or clearly marked as bad cells.

I've never had a battery do this, and it is not only weird, it is scary.

I threw out the suspected bad cell, and just for grins soldered the pack back together as a four cell pack. I put it on my Accucycle Elite charger. It quickly rises in voltage, and peaks out over six volts and the charger turns itself off and makes the sound letting you know the pack is done and ready.

I then put it on "discharge", and you can watch the voltage rapidly drop, until it shuts off after having pulled out about 50 (fifty!) mah. I've done the process several times and it does the same thing each time. Each cell checks out within .02 volts of the others.

This really scares me, because since the charger seems to charge the pack normally, one could easily assume that the battery was charged, ok, and ready to go. And then go lose a plane just as I almost did.

Any battery experts here in this group care to comment? I've got a good number of planes, and now I'm "battery scared." Yeah, I know, battery backers, etc. But I want to know more about the "hows and whys" of this pack going wacko, and how one might predict and/or prevent it.
Thanks,
AV8TOR

Please remember that only a week or so before the battery failure, the battery had cycle tested good. Right before the failure it had been overnight charged at the C/10 rate. It is a two year old Hobbico 1650 pack with Sanyo NiMH cells.

AV8TOR