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Old Logo 20 convert from nicad to lipo

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Old 06-23-2011, 08:27 PM
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Coyote Blue
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Default Old Logo 20 convert from nicad to lipo

Hi,
I have just bought "accidently" a Logo 20 its mostly all good, it will make a good learning heli, itflies nicely but the 3battery packs are 2 x10 pack sub-c nicds and nimh's. The motor is a brushed plettenberg 290/30/11 and the esc is a Kontronic star-opt 40-10-30 its all dated I know but it's in really nice condition and it was cheap with loads of equipment we need for our other helis. My question that someone hopefully can help me with is; 3s or 4s lipo's? The motor specs go up to 30v the esc goes to 40v thepresent voltage is 24. If I connect two 4s lipo's in parrallel, will a fully charged pack hurt the motor at possibly 33.6v?
I do admit I may have to travel back in time to answer this.

Thanks for any opinions
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Old 07-02-2011, 05:07 AM
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Default RE: Old Logo 20 convert from nicad to lipo

Firstly - a 4S pack is always a 4S pack and can't possibly be 33.6V. If you arrange as 4S2p, then the voltage will be 14.8V, but the capacity will be double that of one pack. If it's currently running on 10 Nicads, then that's a nominal 12 Volts, so 3S is too little and 4S is a bit too much. My personal choice would be to go with 4S and change the motor pinion to a smaller one, by one or two teeth, to cut the head speed down to what you want. That should be around 1600 rpm for the Logo 20. The only thing you'll have to be aware of is that the ESC won't be 'aware' of Lipo cutoff voltages, so land as soon as you notice power starting to flag and you should be OK. If you want something better than that, there are several low battery warning devices on the market which will light a big LED when the voltage gets too low.
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Old 07-03-2011, 06:02 AM
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Default RE: Old Logo 20 convert from nicad to lipo

Your heli is probably geared for that motor and 10 round cells so I would go with 2 x 3S packs in series for 6S (25.2V) which is the closest to the original configuration. Going with 2 x 4S in series would be 33.6V and exceed the motors maximum plus over speed the old heli.

A 10 cell pack of NiCd's probably had a capacity of 2400mAh and weighed 700gms back in the day. That's 1.4kg of battery weight.

These days you could order 3S packs with capacity as high as 8000mAh for the same weight.
So you could fly longer, or get some 4000-5000mAh packs that weigh less and will improve the performance of the heli.

5 or 6 years ago I ran 2 Logo 20's with brushless motors which I remember as being great helis. LiPo's were only just coming out and i changed my motor and gearing to an 8S setup which worked great but at the time was frightfully expensive.
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Old 07-09-2011, 05:19 PM
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Default RE: Old Logo 20 convert from nicad to lipo

Thanks for that, I think I got some of my parrallels mixed upwith my series, I'm fine in real life I hope, but my excuse is that I work with inflatable boats not electricity. I should probably have said thatr the2 x10 packs of sub-c's are connected via a loom in series to give me the 24v,I think the two 3sloomed inseries will be best (6s in effect), also can we use them individually or will we have to keep them as a "pack"? I can'tthink why notif you use common sense, maybe connect them together for their final chargeor discharge and recharge. If we can use them individually then we have 3 helis using the same batteries. Thanks again for anyhelp.
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