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Post by gagallagher04401 on Feb 8, 2009 16:41:14 GMT 1
Hi
I wanted to fully discharge the batteries for my cub. I have 2 stock batts, and a 8.7V
Well I put in each pack and let the plane run a bit with a house fan blowing on the front to not let the motor heat up. Well as the batts discharged, the plane motor would "cut out" Then I would have to put throttle down then back up, but would do the same thing, and seems to do it a little sooner with less and less thorottle as the batt seems to discharge. Should this happen?
What is the best way to discharge the bats and is it SUPER important do do with this plane?
Thanks
George
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Post by duck9191 on Feb 8, 2009 17:33:17 GMT 1
with nihm batts you do not need to completely discharge them. it not a bad idea do to it every once in a while the slowy recharge it to help balance the cells but you don't have too.
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Post by flydiver on Feb 8, 2009 17:46:29 GMT 1
Not a good idea. Do some reading here> www.hangtimes.com/rcbattery_faq.htmlBattery use and handling is very misunderstood with lots of opinions flying around, complete discharging being one of the main ones. I think the cutting out you refer to is normal low voltage cut-off. It's so you have some power left to run the electrics. Turning off the throttle and re-arming is to get a bit of power so you can limp home. |
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Post by patmatgal on Feb 8, 2009 18:48:27 GMT 1
Yeah, that's normal to have a little juice left in the battery after the motor quits. That way if you happened to be flying and lost track of the time then the motor would eventually cut off but there would still be a minimal charge in the battery to control the servos as the plane glides to the ground.
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Post by duck9191 on Feb 8, 2009 19:04:53 GMT 1
the low voltage cut on the cub is .8-1 volt per cell I believe which is a good cuttoff. the big problem with over discharging packs is that nicads and nihms arnt balanced like lipos, so if you run the pack down to far a few of the cells could go to 0 volts which is not good for either chemistry. nihms are a bit more suceptable to damage by over charging/discharging and heat is there enemy.
also, don't store nihms dead like the idiot who I just bought a pack from, its not good for them and is a pain in the butt to "refresh" them to working order.
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Post by gagallagher04401 on Feb 8, 2009 19:15:28 GMT 1
Thanks guys.
I had 3 awesome flights today, went througg my 3 packs. I did notice, when the battery pack get low, that the plane becomes very difficult to fly. I had to fight to get it back to me, or soit seemed. Typical? or is it just me?
Thanks
George
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Post by flydiver on Feb 8, 2009 19:55:10 GMT 1
Batteries run down. That's what they do. A fresh warm battery will have noticeably more spunk than an old one that's been sitting around a few days. A NiMh will lose 10% overnight, then 1-3%/day there after. And any of them will have more power for the first few minutes of use and as they near LVC they get pretty lame. The better the battery the better it will hold voltage before it starts to tucker out.
You can start to tell an old or cold battery as they will actually fly better after a few minutes as the chemistry warms it up with use but they don't have that initial good kick when freshly charged anymore.
For best performance, charge or top off right before use.
The Cub barely flies on a fresh pack let alone an almost depleted one. One of the reasons people get all excited about lipos is it flies with some authority. A decent lipo also hold voltage better through the discharge.
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thameth
Flight lieutenant
Posts: 39
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Post by thameth on Feb 8, 2009 23:08:24 GMT 1
So if you're storing batteries, either NiMah or LiPo, and don't know how long it'll be before you use them again what should you do? What levels should you leave each one at?
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Post by flydiver on Feb 8, 2009 23:46:53 GMT 1
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Post by flyerguybham on Feb 9, 2009 21:43:38 GMT 1
Yes, I've definitely noticed that the last couple minutes of the stock battery the flight is pretty sketchy in terms of having smooth control over the plane. Although, I have learned to recognize it and therefore know when to bring it down. I perfected this yesterday when I was on final approach and the LVC kicked in about 6" above the ground :-)
I have been having extraordinary luck with my SC. I have flown about 10 battery packs worth, and have had two crashes (one due to overactive ACT which I have since disabled), no damage, and have had a lot of luck landing it. I'm working now on being more precise with my turns and landings, and also getting more adventurous with flying the plane at further range and also being a bit more aggressive with it. Haven't tried anything fancy like rolls or anything (can stock plane even do rolls or flips?) - waiting for a super calm day when I can take her nice and high first.
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Post by flydiver on Feb 9, 2009 22:47:03 GMT 1
The stock plane will not roll without some aggressive input and maximizing control throws. Even then it's ugly and not worth doing.
It will loop but takes a dive first.
It will fly upside down half way through a loop but ONLY do this WAY UP HIGH, and you need to increase elevator control quite a bit. You sill lose altitude fast and need plenty to loop back out of it.
You want more > look in the modification sections for lots of specifics.
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Post by rcfast123 on Feb 22, 2009 0:11:35 GMT 1
You shouldn't ever try to discharge your plane after already once discharging it. The one and only time you discharge your plane is right when you first buy it. It should say in the instructions somewhere? Discharging is something pilots avoid while flying planes, good things that wasn't a lipo battery, because if it was, you'd burn it and it'll explode. Take Care.
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Post by flydiver on Feb 22, 2009 2:02:17 GMT 1
You shouldn't ever try to discharge your plane after already once discharging it. The one and only time you discharge your plane is right when you first buy it. It should say in the instructions somewhere? Discharging is something pilots avoid while flying planes, good things that wasn't a lipo battery, because if it was, you'd burn it and it'll explode. Take Care. Read that again and think about it. That sentence is full of problems. Of course you discharge it while flying. That's what flying does. A discharged lipo is just an inert pile of chemicals. A CHARGED lipo is the dangerous one. All you risk by a 'simple excessive discharge is ruining it. Sure, short it while charged and you'll have some excitement but that's not the discussion. |
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Post by rcfast123 on Feb 25, 2009 3:13:02 GMT 1
Discharging, by my means, is the way of overusing the battery. I do know you have plenty of flying experience. For example on a 11.1v Lipo, we usually try not to discharge the battery lower than 2 amps. Sorry FlyDiver, but please try not to correct me too many times. I was trying too say over discharging the battery, enough for auto cutoff, where you'll come in for a dive and stick land it. It's not good for the battery as it will burn it and lessen the battery life.
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Post by mrmugen on Feb 25, 2009 4:17:26 GMT 1
Welll I too am confused by your post. First off what do you mean by "we usually try not to discharge the battery lower than 2 amps". This makes no sense. Do not discharge your lipo past 3.0vpc (vpc=volts per cell). You can draw most lipo's that will fly the cub much more than 2 amps in fact it takes about 15 amps to fly the cub at full throttle. I think your confused with your terminalogy. Reread what you typed and tell me again what it is your trying to say. I am not correcting you in a bad way. Just asking you to clarify your post as may new guys will read it and get confused.....it makes no sense.
Kevin
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