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Originally Posted by BrianG
Yeah, most I've seen are linear.
The more cells you use, the more power is wasted by heat on the BEC. The power dissipated on the BEC is (v_batt - v_bec) X bec_current. v_bec is usually around 5-6v. So, if you are using 12 cells (~14.4v) and your servos are drawing an average of 2A, that is almost 17 watts the heatsink has to dissipate. If you only use 8 cells (~9.6v) with the same 2A servo draw, that's only a little over 7 watts. Since the ESC heatsink is usually pretty small, it needs all the available surface area just for the motor controller. Any added power is just going to make it heat up faster/more. If you can't afford or don't want to use a digital UBEC, at least hook up a simple outboard linear regulator.
The internal surface-mounted caps are usually not electrolytic types and aren't quite as sensitive to voltage. But like MetalMan said, the external caps can't really be used to judge the ESC voltage capacity. Maybe the manufacturer got a really good deal on a bunch of 50v caps and decided to use those instead of the "proper" 35v or 25v caps. Also, all those FETs have a max working voltage as well, and unless you can read the part number and get a datasheet for them, there is no way to really tell.
But if you want to experiment, and have deep pockets, then more power to you! :)
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Right, so that's why it seems the BEC is the limiting factor, not the other components (to a reasonable level.) Remove that limiter, and you can push a bit higher. I'm not suggesting that the ESC is merely rated by their caps, else BKs would be rated as a 50V esc.
By disabling the BEC you are removing alot of extra heat, I wouldn't be surprized if it could handle an extra 2.4V (that's all we are really talking here.) To the BEC, that is several more watts (5 or more), but the rest of the system would prob be within specs for that small amount of voltage (its not like they are using 15V caps.) Considering it is coming from a CC rep/engineer (he's mentioned in the CC thread on this board) this is prob not pie in the sky. The CC ESC is rated upto 100A, it would seem capable of running a 8xl or 9xl motor on 14 cells if done with care.
I had a GTB/5.5 that I ran on 7 cells fine, tho Novak only rates them for 6 cells. ;) It would not make sense for a reputable dealer to sell a product that was right on the edge of design capacity. You build in a safe margin that is reasonable as budgetary constraints allow. It would be an interesting experiment, and if it worked well, it would be a very sweet controller for a mild setup.