12 Servos - Power supply

Hi - I'm new to this world so need some help with power issues! I'm trying to run 12 micro servos doing basic sweeps off an Arduino uno with a adafruit 16-channel 12-bit PWM driver (Adafruit 16-Channel 12-bit PWM/Servo Driver - I2C interface [PCA9685] : ID 815 : $14.95 : Adafruit Industries, Unique & fun DIY electronics and kits). The arduino is powered separately. Since, I want the setup to be portable, is a duracell 6v 42Ah AGM battery good for 2 hrs @ about 2Ah a servo? Do i need capacitors/resistors or voltage regulator in series to be safe?


Typical micro servos draw at most 200 mA so 12 would draw 2400 mA if they are in constant motion and under full load. If you are using a 42 Ah battery, you would draw 42 Ah/2.4 A = 17.5 hours. I use the same module and always run the battery (9.6 V 1800 mAh) direct without a servo. However, I did find the following in the documentation so you may want to add a 1200 µF capacitor to the board if you are concerned.

Adding a Capacitor to the thru-hole capacitor slot
We have a spot on the PCB for soldering in an electrolytic capacitor. Based on your usage, you
may or may not need a capacitor. If you are driving a lot of servos from a power supply that dips
a lot when the servos move, n * 100uF where n is the number of servos is a good place to start

  • eg 470uF or more for 5 servos. Since its so dependent on servo current draw, the torque on
    each motor, and what power supply, there is no "one magic capacitor value" we can suggest
    which is why we don't include a capacitor in the kit.

Thanks jseery. do you know how many Volts would that 1200uF capacitor need to be?? (I don't want it to explode :P) Also, are you sure about those calculations - according to this page (Powering Servos | Adafruit 16-Channel PWM/Servo HAT & Bonnet for Raspberry Pi | Adafruit Learning System), each servo can take 1Amp under load(stall?). anyway, i couldn't find anywhere else that someone used an AGM battery so I'm thinking of going with a 6v, 5000mAh Ncad battery pack which is a lot smaller.. hopefully that's enough!