I'm running 32 servos. I wish for them to be as fast as possible. My microcontroller runs at 5 V. My powersource is a 6 V lead battery. I could run the MCU and the servo drivers and all other electronics on 5 V, but I would like to run the servos directly from the 6 V battery, because they might be very hungry. But a 6V lead battery is not 6.0 V, but maybe some 6.4 V. And since it's a nice lead battery, probably meant for small combustion engines with starter motors, it won't drop the voltage after some amperes of load.
The specs for the sg90 servo say:
Operating Voltage: 4.8 ~ 6.0V
Will I toast the servos, if I run them directly from the 6V lead battery?
This is the Minimum and Maximum voltage your servos can take, using more or less than what the manufacturer suggests risks breaking the servos. I personally wouldn't take that risk. But there are adjustable voltage regulators or buck converters that can change the amount of voltage that goes to your servos, so if you put one in between the connection between the battery and the servos, you can change how much voltage goes to the servos so you can remove the risk of damage.
Here is a link to a Buck converter on the Arduino store. 20W Adjustable DC-DC Buck Converter with Digital Display — Arduino Official Store
You should not exceed the manufacturer's ratings. If you do and the servo electronics survive, the motor life will be nevertheless be shortened (true of all brushed DC motors).
Hobby servos, especially the SG-90, are cheaply made and not intended for continuous use. The gears and motors wear out rapidly.
If the project is designed for continuous, long term use, you should expect servo failures to occur at any time, and for the failure rate to increase with the supply voltage.
To get a better idea of the failure rate, set up an SG-90 with the Arduino "servo sweep" example, and run it continuously until the servo fails. For the best overview, do this with several examples.
Put a high current diode in series with the feed to the servos from the battery. Drop will vary from 0.4-0.6 volts depending on current demand. With that many servos, I'd probably be both fuse-protecting, and diode-dropping, batches of a half dozen or so. You are fuse-protecting your system, correct? Not direct wiring from battery to each servo? Right? Right?
Well, I would have wired directly from battery to servo, if the servo could take say 7 V. But I guess the fuse protecting would be really good to have in any case, since the amps that the battery can provide are huge.
I guess I try my LM2596 first, even though it might drop too much as a minimum.