Quick question … I have my brat together and am running through a few of the sample SEQ setups for the brat (working great) … I have made all the adjustment for offsets (followed tutorial) … most of the time the bot is very quite when all servos are set to 1500 (home) … However some times I notice a lite humming/pulsing from the servos (mostly knees) … is this nomal for HS-645MGs? Is it bad for the servos?
The humming is normal and it just means the servo is correcting for a position that may have some resistance. It’s not going to harm the servo unless it’s screaming and doing a lot of work. Best to test if the servo is getting warm just to be sure, but it should be no problemo. 
Sounds like you did a good job with the assembly if its quiet at home position. Yeah, servo whine is going to happen when holding a position under load. Not to worry as long as they don’t remain in a strained position for an excessive amount of time. It depends on the amount of strain. A small amount is relatively harmless. I usually touch the servos with my finger to make sure there are no problems.
So a little noise is ok … just as long as the servo is not getting really warm … Right?
It’s not a critical situation, but I’d try to figure out why it’s making the noise. As Jim said, a servo or servos are encountering resistance on the way to the desired position. What is the source of the resistance? I’d at least attempt to minimize it.
Most likely the source is gravity!
My servos hum all the time holding position, and I have checked its not mechanical.
(When it is a mechanical stall, the humming gets REAL loud…)
Yes, that is absolutely correct.
The humming is normal and it just means the servo is correcting for a position that may have some resistance.
Quick question … How much run time should I be expecting to get from a BAT-03 power supply … seems like I can work with my BRAT for about 45 - 60 mins and then it starts acting very odd (falling down, sporatic servo movement, weak movement) then I have to recharge … And things are fine then. (Standard BRAT setup)
The battery can deliver 1.6 amps for an hour. Now if you have just started using the battery the capacity will improve as you charge and discharge it several times. 1.6 amps is a rough average of 250mA per servo, so that’s not bad. 