Nov 06, 2001, 07:28 PM
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montreal quebec Canada
Joined Sep 1999
1,254 Posts
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I have been flying the CP1700s for much of this season and I would like to pass along a couple of observations. First, they are really about 1500mah under our loads. Just like the RC2400s are really 2200s. These cells probably put out their nominal capacity when discharged at a few hundred ma but at 30 or 40 amps that is all you get.
Second, there are a few guys who have burned them up by pushing them hard. They seem to have internal resistance values somewhat higher than the 1250s. I make sure to cool mine between flights with a fan, as I think I am into the 40 amp range (not sure). But lately they have been falling off. I am not sure why this is and will investigate this winter. Other guys are using them at ridiculous current draws and say they are fine. I don't know why the discrepancy. Steve Neu has apparently discussed this in S&EM but I haven't read is column. Maybe there is less consistency in the mfg of these cells? So be careful and don't assume that you can beat the crap out of them and they will just take it. Try to cool them down after the flight. Remember that they get their hottest shortly AFTER you land.
So be aware that you will not have nearly the flight time with the CP1700s and that they might not have the "punch" of the 2400s. Actually, I believe the 2400s still have the best power density and are the cells best capable of taking our sort of abuse.
However, if you want to fly and shed some weight and don't mind giving up duration to gain performance, this is a good way to do it. By throttling back after a low pass you can still have a reasonable flight time. That is what I have done with the Hacker-powered Sabre. It is now 150 W/lb+ and is a ball to fly. I still get 4 minute+ flights.
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Last edited by sblack; Nov 06, 2001 at 07:32 PM.
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