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Charging Lipos...

Old 08-10-2007, 05:34 PM
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Tinman
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Default Charging Lipos...

I'm charging two lipos for a couple flights tomorrow morning.

Do you usually charge them the night before and then hit them with the charger right before you fly? Is that necessary and does it hurt the battery if you do that? ??

thanks
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Old 08-10-2007, 05:45 PM
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adamdb
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Every Lipo tutorial I have ever seen says DO NOT top them off. The self-discharge rate is so low on lipos that they will lose very little overnight. Even over the course of a month or two they won't discharge enough to need topping off.
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Old 08-10-2007, 06:14 PM
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What adamdb said is true.

Maidening that SD?
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Old 08-10-2007, 06:25 PM
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Thanks adam, thats what I thought, just wanted to make sure.

G, yep tomarrow is the day. Got everything tripple checked. I'm going to try to fly it with a 2150 Lipo. Fits in there really well and the CG is right on. I'll let you know how it goes, I'll try to get some pics.
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Old 08-10-2007, 06:32 PM
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Good luck with the maiden Brian. You'll do great.
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Old 08-10-2007, 06:35 PM
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Thanks Tom, after flying your gravity defying Mustang a few times, I think I got this one in the bag
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Old 08-10-2007, 06:41 PM
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I have always heard/read that the best battery care is to charge them full in one go and drain them all the way down in one go as well. IF you do multi session charging you can shorten the life and/or reduce capacity. Once I charged my lipos after a flight and didnt use them for a week, maybe two, and they were perfectly fine. I got full flight times out of them.

Lipos tend to hold their charge VERY well. They have the slowest non use discharge of all the types you can find out there (nimh, nicd, li-ion)
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Old 08-10-2007, 07:34 PM
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Originally Posted by Tinman View Post
Thanks adam, thats what I thought, just wanted to make sure.

G, yep tomarrow is the day. Got everything tripple checked. I'm going to try to fly it with a 2150 Lipo. Fits in there really well and the CG is right on. I'll let you know how it goes, I'll try to get some pics.
Congrats and glad to hear it. With that 2150, you'll probably be able to fly until your neck hurts!

The only thing to watch for is if you ROG, let her lift off on her own. If you horse her off the ground, she'll torque left and ground loop. (That's my experience anyway).

Also, if you've got mixing capability, add a little rudder mix with the ailerons ... this plane likes coordinated turns.
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Old 08-10-2007, 07:57 PM
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Thanks for the info G.
I plan on ROG takeoff since I'll be flying at the ball field. I'll keep fast and won't yank her off the ground.

Good idea about the rudder mix. I never thought about doing that. Do you have a specific percentage that works?
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Old 08-10-2007, 08:40 PM
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Originally Posted by Tinman View Post
Thanks for the info G.
I plan on ROG takeoff since I'll be flying at the ball field. I'll keep fast and won't yank her off the ground.

Good idea about the rudder mix. I never thought about doing that. Do you have a specific percentage that works?
I have a 60% mix, but I think that's a bit on the aggressive side. Use that as a starting point and work back from there.

I like it there but it is VERY responsive (almost twitchy) at that setting. I may try reducing it at some point, but I never think to when I'm actually at the field.

The difference in roll rate between rudder mix and no rudder mix is impressive.
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Old 08-10-2007, 08:44 PM
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I was wondering about your mixes...do you have it mixed in so that when you apply rudder you get some aileron to prevent roll or do you have it so that when you aileron you get rudder or both?

Seems to me the common sense way is to have aileron mixed in when you apply rudder.
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Old 08-10-2007, 08:50 PM
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No, the opposite. It mixes in a bit of rudder with the aileron to produce a coordinated turn, and counteract any adverse yaw created by the ailerons.

It'd probably be possible to set up a mix to apply opposite aileron (to counter roll coupling) to your rudder inputs if you wanted to do side-slips ... which I think is what you're suggesting.

Adverse yaw is the tendency for an aircraft to (for instance) yaw left momentarily when right aileron is applied. This occurs because it's "easier" for the inside wing to dip than to raise the outside wing. This causes additional drag on the outside wing which causes the aircraft to yaw to the outside of the turn momentarily until other forces combine to counter it.

You can counter adverse yaw either by having a bit of differential in your ailerons (they go UP more than they go DOWN), and/or by applying rudder in the direction of the turn.
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Old 08-10-2007, 08:52 PM
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I was just thinking...what if you want to roll and have just aileron input but you mixed rudder with your aileron....that would not work. (Thinking of slow rolls or snap rolls, maybe you dont mix in rudder for planes doing roll aerobatics?)
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Old 08-10-2007, 08:59 PM
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Originally Posted by Lip84 View Post
I was just thinking...what if you want to roll and have just aileron input but you mixed rudder with your aileron....that would not work. (Thinking of slow rolls or snap rolls, maybe you dont mix in rudder for planes doing roll aerobatics?)
I do have a switch on my TX programmed to turn the rudder mix on or off. However, the rudder mix (on my plane anyway) doesn't adversely affect the roll characteristics ... in fact, I find it dramatically increases the roll rate. If I flip off the rudder mix, the roll rate slows down, and I can do slow rolls.

Snap rolls require rudder input anyway (full rudder, full aileron, full elevator usually), so it doesn't matter in that case. Any rudder input I put in on the left-stick overrides the mix anyway.
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Old 08-10-2007, 10:51 PM
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Great info G. Also like your explanation on adverse yaw. Not to many people know what that is.
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