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Post by cjg on Jul 15, 2007 21:35:20 GMT 1
Okay, so I read that you should charge your batteries within a few hours of flying. (NIMH) Also, my pack says to keep warm before flying. So I try to charge before flight but sometimes weather and stuff cancells your flight plans. So today I ended up with all four of my batteries fully charged but then it started raining. So my question is, is it okay to pop em back on the charger till it reads a full charge a few minutes before flying as I know they slowly lose their charge over the next couple of days? A multi meter won't really help you that much. The charger that comes with the SC is in fact and cheap little charger. I have an ICE and it is nice, but you probably don't need that much, especially since it requires a power supply. Try this charger out for better results with a variety of batteries: www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXCLD5&P=ML |
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Post by duck9191 on Jul 16, 2007 1:01:23 GMT 1
its not 100% accurate to check with a dvm, a 8 cell batter is sold as 9.6 volt, but thats there nominal voltage, but the battery should be higher then that when fully charged. another good way to test a known good batter is that it should start to get warm when almost fully charged as the resistance in the batter goes up when the cells are fully charged.
there is a ton of differnt chargers, i would go to a few of the big hobby sites and look at whats offered. you can use a car/truck charger with the batteries along with the ones sold for flight, there the same thing just a few differnt features to market to one crowed over the other.
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Post by thecreepa117 on Jul 16, 2007 3:57:35 GMT 1
yeh just bought a cheap 10 dollar mm today and I'ts weird but it reads about .5 to 1.0 volts over what the battery is specified as. Also, a 8.4v battery that has been more or less discharged is reading as having a full charge? Is there something I'm missing or did I just accidentally fly\test the wrong battery as my ex called me during flying and I made an unexpected landing. Oh, and how important is totally discharging batteries after use as I try to run mine down to about 1/2 throttle after landing before the auto cut-off to try to discharge it well? Do I need a charger that will discharge my batts to get more life out of them. Sorry for the countless questions but your help is appreciated, man.
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Post by thecreepa117 on Jul 16, 2007 4:19:10 GMT 1
yeh, see I totally discharge my battery at about 1/8 throttle. But it still reads about 8v on the meter. So, is a battery always at the same voltage, and do I need another way of reading whether or not they are fully charged?
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Post by duck9191 on Jul 16, 2007 4:53:39 GMT 1
8.4 volts is at 1.2 volt per cell, fully charged 1.4 volts per cell is normal. so on a 7 cell 9.8 or so would be normal for a charged battery, but it depends on the battery and its condition. when you discharge a battery under load the voltage drops, and when you let them set they will recover some so it may read a normal voltage.
also the charger that cjg gave the link for are nice too. there is tons of options.
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Post by thecreepa117 on Jul 16, 2007 9:04:54 GMT 1
I assume you were just writing too fast when you said a '7 cell 9.8v'. or is it that I had a really bad day and therefore too many shots. Are you saying that a 7 cell might read 9.8 instead of 8.4 when fully charged? I'ts just that the 'dead' stock battery (8.4v) is stilll reading about 8.4v on my mm? I'm just confused as to why It is stiill reading that it is putting out 8.4v when it was dead enough to cause me to crash today. (After moter cut-off, it decided I wouldn't get any more motor even at 1/4 throttle after re-setting. If I knew that, I would have just dead-stick landed it on the pavement like I usually do. Cracked the cowl, and a little Pride, but no big dea. Didn't even scratch the new p-51 mustang ptop I installed today (although (I believe its the same prop as the og SC)l God this plane is a dream for a beginner,.
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Post by duck9191 on Jul 16, 2007 16:32:13 GMT 1
it may read 8.4 no load, but kick in you motor and see what it reads, when you add a load to a battery the out put voltage will drop, thats why when your battery runs down you can run it longer at 1/4 throttle since there isnt as much of a power draw it doesn't pull the voltage down as fast and doesn't hit the lvc.
its normal for a battery to show a higher voltage then what they are sold as, since as soon as there hit with a load the voltage will start to drop
don't feel bad, yester day i garbed the wrong battery too, got up in the air fine but as soon as it got around the tree i heard the motor drop off quick, i ended up flying though the tree lol. no damage just broke the plastic at the strut mount.
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Post by thecreepa117 on Jul 17, 2007 0:09:19 GMT 1
Ahh, it's slowly starting to come together. I ordered another cowl today. Think I'm gonna paint the cub like some kind of green you would see in the Vietnam era. Anyway, thanks for the info on the charger at top of page guys. Think I'm about to pick her up.
So, now that I understand that the voltage immed. drops under load, where do I want to connect the multimeter to read the voltage when I kick in the motor? The motor leads?
I'll have to go look. Now I want bigger wheels and I was looking at the Du-Bro wheels. Gonna have to do some measuring.
Oh and sorry about your visit into the tree. I almost had the same problem on a touch and go the other day but (somehow) pulled out of it with full throttle, full up elev., and full right rudder. I'm telling you man I trimmed those leaves. Oh yeh, and my crash was caused by the lvc not allowing me to re-start the motor at about 1/4 throttle. Any ideas why it wouldn't re-start as it always had in the past?
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Post by duck9191 on Jul 17, 2007 0:27:23 GMT 1
your battery may not have recover to above the lvc, or maybe in the panic of it all it didnt rearm the esc. i didnt have a chance for either, owell it was funny.
you could check at the motor connection so you don't lose a finger, but i wouldn't worry about checking it too much, just make sure that right before your charger kicks off that the battery is warm, that will tell you its getting close to be fully charged.
du bro wheels work well, just need to make a bushing so they don't wobble around to much.
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Post by thecreepa117 on Jul 17, 2007 3:05:19 GMT 1
yeh man I am learning more and more. I took off the cowl and prop and saw how the motor drew power with the mm. I did the same to the back side of one of my un-glued batt packs to see how it lost voltage under load like you said. I just did all of this to try to feel my way around electrical if you know what I mean. I could rip a yz125 in half and have it put together working like new, but as to RC, I am very uninformed and kind of enjoying learning something new.
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