servo amp draw?????????????
 

I have a futaba 3305 heavy duty servo, and I noticed in the specs it to only be used with ni-cd batteries, due to high amp draw. I'm confused. doesn't everyone run lipos in today's brushless powered vehicles, because the brushless ESC's draw a high amp current? Why wouldn't the same be true for servos? Are they saying the voltage of a lipo is to high, and this will burn up the servo? Please explain. If I do run this servo in a 1/10th scale buggy, using a 2S 4000-5000mAh lipo pack, what do I need to do? Should I run a voltage reg. and a power cap, and if so, which ones do you guys recommend? Thanks in advance, guys!

It's a 6v servo and so you wouldn't run it directly from a 2s lipo pack however esc BEC's are 6v and so it would be fine running from the esc. Most esc have a 3a supply and so that should be sufficient. If you get glitches or brownouts where the servo seems to struggle you can try a glitch buster power cap (any of them will work) or run it from the lipo with a seperate BEC however I doubt that is needed.

I've ran the 3305 servo back when I ran nitro and used a lipo with no problems. You shouldn't need a bec for it.

The 3305 is one of Futabas oldest servos still being made. Back when they were "high tech", battery technology was still a little lacking. The 4AA holders were the norm, and they weren't that good at supplying a lot of amps consistently. Once you strapped in a 5 cell NiCD pack it spread out the amp draw between 5 cells instead of 4.

Ummm a 5 cell pack has the cells in series so the packs ability to deliver current remains the same between a 4 or 5 cell pack. I think you meant to say the servo performed better because you went from 4 AA nicds at 4.8v to 6v 5 cell nicd thus increasing the voltage and lowering the servos requirement for current. Higher supplied voltage less demand for current (ohms law) :nod:

It's also my understanding that the warning is for smallish nimh receiver packs, as they began to replace nicad packs, most commonly used with nitro RCs. I wouldn't expect any issue with an electric RC. I don't have that model servo, but I have many Futaba servos that have the warning that work great in my electrics, without any glitch buster or other aids. With either nimh or lipo main packs.

I highly doubt the current is reduced when the voltage is increased. Servo torque and speed ratings generally improve significantly at higher voltage, suggesting the power level has increased, not stayed the same.

In the general case the higher voltage/less current deal only happens if the power is maintained at the same level. Which usually requires a change in the load. With the same load, higher voltage drives higher current.

Thanks guys! I'm selling some of my RC stuff, to fund my full size car. I was building a street stock for the dirt oval, out of a B3 buggy. My friend is wanting to by the car, and wants me to include a servo with it. It's the only metal gear servo I have, that I wasn't wanting to hold onto. I don't like to sell things, if I'm not sure about them. Thought I'd check with with the experts, before I sold him something that he'd have problems with later.:nod: