Let's Make Robots!

Li-ion 7.4v and servos

At this time, I make a humanoid robot. This one: http://letsmakerobots.com/node/27414 and now it's time to use battery power.
I have a battery 7.4v Li-ion 3200mah (2 x 3.7v), the type is PL-5545135! My question is: When the battery is full supply, the voltage is 8.2v. May the servos have trouble or destroy?

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The servo will probably be able to operate, but at those voltages will operate faster and thus will wear out much faster. Also, I am unsure as to if the circuitry will be able to handle such voltages. A 5V regulator will be the best route to go.

What is the highest current 5v regulator one can find? If he runs more than a few servos on even a 2A version he may run into current issues. Would a pair of properly sized diodes in series not be a better call in the case of servo power?

Yes, diodes would work great too, but won't give you a linear power output when the battery drops. There's the LM2679T-5 which is a 5A 5V regulator, but would require a bit of work to get it working. Diodes would be quick and easy.

I have been working on those multiservo robots and the best works for me is using 15A 6V switch regulate UBEC. In my experience I run up to 24 servos with no problem. If you don't use regulator you might burn your servo easily with fully charged 2S Li-XX batteries. I learned that by hard lesson and burn 3 expensive servos in a day.

Good luck to your red dragon. ;)


My robot,has got 20 metal standard servos,2 plastic and 4 micro metal.They have many Amp..The ubec http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=6233  is perfect for my robot

I would measure current draw for each servo, then determine the greatest load in each system. Worse case, is that you'll need two of those UBEC's hardmouse posted.

yes i need ubec 6v 8A, thank you