On Thu, Dec 29, 2005 at 11:14:13AM -0500, [EMAIL PROTECTED] wrote: | In fact we seldom run any specific voltage for a consistent period of | time in our use of the models.
Well, you probably do if you're using a voltage regulator or a BEC. But beyond that, you're right -- a 4 cell pack will start at 5.6 volts and drop to about 4.8 volts (at which point you'd probably better be thinking about charging sometime soon. You may have 30% of your capacity left, but you don't want to push it.) | A voltage regulator insures that your digital servos and RX don't get | too much of a good thing, and yet keeps the optimum voltage maintained | for not only performance but more importantly OPERATION! Some digital | servos need to have a minimum of more than 3.6v to operate at all. And most receivers will peter out at voltages around that point as well (though there are a few low voltage RXs meant for single cell LiPo use.) If your (4 cell) battery pack is at 3.6 volts, either 1) it's really close to totally dead, or 2) one of your cells shorted out. #2 is rare -- it's more common for a cell to fail open or to at least develop a really high internal resistance. Fortunately, that usually happens gradually and to older batteries, so some battery maintenance will detect it and take care of it in most cases. If you had a 5 cell pack and it was giving 4.8 volts, it's just as dead as the 4 cell pack at 3.6 volts. Sure, it may still run your RX and servos, but it's going to be down to 3.6 volts and lower within a very few minutes ... perhaps in less than one minute. Personally, if safely/reliablity is what you're after, I'd suggest going for two smaller 4 cell RX packs rather than one bigger 5 cell RX pack. (Now, if you want more speed and/or more torque, then go for five cells if your gear can handle it. But it probably costs you more in reliability than it gains.) | Try your system with a three cell pack to find where your loads take | the system and your servos. So using 5 cells with a voltage regulator | can provide a level of safety and keep your servos operating at the | torque and speeds you paid for listed on the box. Isn't the idea of a 5 cell pack to get your servos operating *beyond* the torques and speeds listed on the box? | Those who use 5 cells without a regulator can be torturing your | system (5 cells peaked exceed 6 volts) 5 cells peaked is right at 7.0 volts. If your 5 cell pack drops to 6.0 volts, that's 1.2 volts per cell, and your pack is likely to be over 50% discharged at that point. | that means your system...connectors, switch, voltage regulator in | your RX, the power pin lands on the board of your RX connecting | all the servos to the power, wing connectors, servo amplifier and | servo motor brushes are getting one heck of a power jolt at | first... The switch, pins, and connectors don't care signifigantly about 4 cells vs. 5 cells. Sure, 5 cells will give you higher currents and therefore more resistive heating, but that's pretty much insigifigant for a RX pack unless something is very wrong (like having some stalled servos or a short circuit.) (Now, the electronics, voltage regulators, RX, amplifiers -- they may care.) | Its just about wire and the energy its submitted to, low power, low | glow :-) Personally, the only thing I want glowing on my plane is the LEDs I put on it so I can see it at night. That, and if it's a glow plane, well, the glow plug is allowed to glow, though you can't see it. Anything else glowing is probably a bad thing. (A few sparks in a brushed motor -- that's permissible as well. But it's not really glowing ...) -- Doug McLaren, [EMAIL PROTECTED] An unbreakable toy is useful for breaking other toys. RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
