Jeff Winder asks: >Seems like a lot of HLG folks out there are running 3 cell packs in their designs. I assume this to be 3.6 volts. Is this enough voltage to run a 2 micro servo system with? Does the receiver need to be a certain type....Hi-tech 555 works better in a 3 cell configuration verses a JR 600? Since the current will remain the same between a 3 cell pack and a 4 cell pack of equal capacity cells, will the 3 cell pack run as long, but have 'less' power to move the servos...i.e. slower response, less force applied to tail surfaces? < Since Joe Hahn and I were among the instigators of this trend, I think we can inject a little hard data into this discussion. Since 3 cells have less voltage than 4 cells, the receiver and servos usually (with at least one exception, more on that in a moment) draw LESS current on three than on four. As a result, a 3-cell pack USUALLY lasts longer than a 4-cell pack using the same type of cells. For example, we fly a lot with either a Hitec 555 or 535 and a pair of HS-50's, or with a Berg-6 and a pair of HS-50's. We also fly quite a bit with those recievers and four HS-50's in flaperon HLG's. We've had very good results with all of those on both 3 cells and 4 cells. We haven't tested the JR receivers for this, but our other experience with them suggests that they might perform similarly. Yes, a 3-cell pack THEORETICALLY results in less servo torque and less receiver range, but we have NOT seen a measurable decrease in either of those parameters in actual practice. The servo torque has been completely sufficient for flaperons on our designs (both the Wizard Lite and our latest 4-servo prototype designs), and the range has been far enough to pass the same ground range check and the same distances in flight, all the way out to little bitty specks. Then again, my eyes aren't as good as they used to be, too much time in front of the computer I guess! The amount of warning at the end of a charge seems to be a little better with three cells; the total voltage drops low enough to make the servos get sluggish at a slightly higher point on the cells' discharge curve, resulting in a little more time left before they die completely. With these receivers and two servos, we typically get in excess of 40-45 minutes per charge on a 50 mah 3-cell pack. A 3-cell 110 mah pack will go comfortably past an hour for us. A 50 mah 4-cell pack delivers a bit less, usually about 30-35 minutes. Note, your mileage may vary; the current draw in flight depends a great deal on your flying style. If you overcontrol a lot and constantly stir the stick around unnecessarily, you will use up all the available "juice" somewhat sooner! OTOH, all the extra drag you're causing will probably make your flights somewhat shorter, so you might end up with about the same number of flights per charge! ;-) We usually do a bench test (turn in the radio and Tx, start a timer, and stir the stick continuously until the servos get sluggish) to get a baseline time-per-charge before we flight test a new combination. We have flown some models all the way to battery failure in flight (I have a very big "back yard", and our new Spectres are so light that they don't break very easily) and we've found that we consistently get as good or better flight times than the bench test times. On four servos driving flaperons the times go down to about 14 to 17 minutes per charge in our tests. The extra servos and the larger control surfaces simply demand more power. If you do a lot of testing with this setup and find that you're consistently getting AT LEAST this much time from them, it's still adequate for a typical 10-minute contest round. It might be worth the weight savings for a flyoff in light air. In general, though, for four servo HLG's we usually use three 110 or 150 mah cells these days. The cheap source for 110 cells is Eveready or Panasonic brand 9-volt rechargeable nicads. Each of these contains six cells, enough for two flight packs. Just cut the top off the case, remove the cells, split the pack into two 3-cell packs, clean off the unneeded straps on the ends, solder on some pigtails (quick and careful or you'll ruin the cells), and wrap them up with polyethylene tape or shrink tubing. The two sets of pigtails and connectors will probably cost you more than the batteries! For charging, I just use the plug-in wall charger that comes with the radio, and unplug them as soon as they start to get warm. The exception seems to be the FMA Tetra receiver with FMA S-80's, or the other GWS "clone" servos such as the Cirrus CS-10 and 20, et. al.. A friend of ours tried a Tetra and two FMA S-80's on three 50 mah cells, and got a battery life of only EIGHT MINUTES! This is not enough for a single contest round. We've run some tests of our own with CS-10 servos and gotten similar results, although the Tetra receiver itself seems to be a big part of the problem. For some reason both these receivers and these servos seem to be "current hogs". In summary, for the rather miserly needs of Hitec and Berg components, 50 mah 3-cell packs seem to be the best for Mosquito class models. 2-servo 1.5 meter HLG's also do well for us on 3-cell 50 mah or 110mah packs, and for our current 4-servo models we generally recommend 3-cell 110 or 150 mah batteries. Other models, including our older Wizards with the short flaperon horns and stiffer flaperon hinge layups, need more torque from the servos. For these you may need 150 mah cells and/or 4-cell packs. Don Stackhouse @ DJ Aerotech [EMAIL PROTECTED] http://www.bright.net/~djwerks/ RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
