A project I’m working on requires the use of an arduino board (most likely a UNO) and three servos. Their operating voltage is 5.0-7.4V with a max current of 2.3A. (I’d need atleast 6.9A)
First I’d like to know if it’s possible (and more beneficial) to power both separately.
I’m looking for a battery which could power everything, and I’m having trouble figuring out what batteries to use. I understand that batteries have C-ratings which tell you how much current a battery can supply, but most of the batteries I see don’t have C-ratings listed (or I’m just blind). What batteries should J use? Am I just not looking at the right specs?
Try a 10AmpHour EBIKE battery with a 5VDC USB port. The USB port can source 2.5A and the battery has a BMS, so the battery will stop discharging at a safe level. That will give you standard to measure against.
Power the servos separately, and don't forget to connect the grounds. By comparison, the power drawn by the Arduino is negligible.
The power supply must be able to easily supply the full 7 Amperes, as servos briefly draw the full stall current every time they start moving. Battery packs for RC vehicles will do the job.
Hopefully several hours, or at the bare minimum an hour. I just don't want to be buying so many batteries, so maybe a rechargeable one? Actually, then at that point maybe I should just use a power cord. Thoughts?
I've seen some of your other responses on posts with similar questions where you suggest a step-down buck converter. Would that be needed here? If so what would you recommend?
I remember hearing that batteries may output slightly higher/lower voltages than listed and so I'm worried about whether it would negatively affect the servos.
Servo and battery voltage ratings are nominal, and actual battery voltage changes quite a lot during charge and discharge.
A single LiPo cell in good condition and rated as "3.7 V" has a voltage versus time discharge curve that looks similar to the following for light, medium and heavy (green line) discharge rates:
