Any advantage in running a UBEC w/ 6cells? - RC-Monster Forums

**Any advantage in running a UBEC w/ 6cells? -** 03.01.2007, 09:00 PM

Quick question, is there any advantage in running a UBEC when only running 6 cells? I have a UBEC left over from my E-8th scale that I could put in my BK4018/Lehner5300 TC3 if it would at all help with anything. I figure it might help take some stress off the esc or help with cooling but not sure.

BrianG · 03.01.2007, 09:07 PM

Not really. It won't hurt, but won't help that much either. As the supply voltage (battery) gets closer to the output voltage (6v), the advantages of a switching UBEC become much smaller.

If you are drawing an average of, say, 1A on your servo (and this is an extreme figure), you'll lose about 1.2w as heat. And it will be less than that because servo loads aren't constant. This equates to about 83% efficiency, which is close to a switching UBEC efficiency of about 85%.

MetalMan · 03.01.2007, 10:21 PM

But, the switching regulator might not operate at an input voltage that's the same as its output voltage. Linear regulators can be had in a LDO (low dropout) version that allows you to use an input voltage close to the output voltage. I don't think I've ever seen a switching regulator with this feature.

BrianG · 03.01.2007, 10:58 PM

IIRC, the one in Mike's store goes into "pass-thru" mode if the input voltage gets too low...

Or, if you were the adventurous sort, you could use a zener diode, pass transistor, and a couple of resistors to make a low dropout regulator. :)

MetalMan · 03.02.2007, 12:07 AM

But why do that when you can get something that works the same but is in such a smaller package? :)

BrianG · 03.02.2007, 02:15 AM

Well, the parts to make a LDO linear regulator are available locally while a LDO regulator IC has to be ordered. :) Besides, with a little creativity, a homemade one can be just as small. But that's just talk really. I'd just use a regular 5v regulator (LM7805) if being used in a small vehicle where current draw is no more than 1A average.

Serum · 03.02.2007, 02:46 AM

Yeah, a voltage regulator, like Brian suggested, would be an okay choice for the few volts it has to kill.

08:26 PM

Ok you guys definetly lost me...
What benefit would an LDO regulator or a 5v regulator have for me?

BTW I'm only running a hitec hs-625mg steering servo so its nothing thats gonna be putting a crazy draw on anything.