Please help me. I am make a robot with 8 MG996r servos and need a battery for them that is not too big and is light.
The MG996R stall current is about 2.5 Amperes, which the servos briefly draw every time they start moving.
For best results, the servo power supply should provide 4.8 to 6V at > 20 Amperes. Anything less than that can lead to a twitching mess. RC hobby suppliers sell appropriate battery packs.
Please help us help you. How big is "too big" and what weight is "too much"? Are all 8 servos required to move simultaneously? If not, how many must be moving at once? What other peripherals are attached? How long must the battery usefully last?
All of the servos have to be moving at once. it has to be under 1 kg
Then you have no choice but to ensure that the power supply is capable of delivering 20A.
2 Likes
If your servos will be in 'stall', i.e. under significant physical pressure to change their position, which they must resist, then you're faced with the worst possible peak currents.
How much current, and if only four servos at once will a battery work
It's too implementation dependent to spout a number at you, but you'd best do some testing with a mockup to figure out what you're up against. I have in mind a 'spider walker' when you reference 4 vs 8; that does reduce your top currents, but you need to do some testing.
I'm sure others have more useful advice, I've not much experience in this area, so I'm working from what I know - and I'm out of that.
Good luck!
It is a robot dog based off Spot Boston Dynamics
2.5 Amperes per servo.
Not possible. A 10Ah e-bike battery (you need current) will weigh about 3kg without packaging (just cells, BMS, nickle-strip and wires). You will get up to 30 minutes of use if your servos are moving the robot. Then you will need three hours to re-charge.
1 Like
the video helped but I don't know how to solder.
Adafruit and Sparkfun have good soldering tutorials. It is an essential skill for this hobby.
The author is spot-welding (see 11m32s) the nickle to the batteries, not soldering. Soldering is just for the BMS and wires onto tabs.
The alternative to making your own battery is to buy one. About US$500 for a 10Ah e-bike battery from a reputable battery manufacturer.
could you recommend any spot-welder
I would only recommend the spot welder in the video, if you plan on many batteries. The following spot-welder, you need to build the battery in sections, slowly.
Lipos of reasonable size will deliver high start up currents easily.
Problem could be that a 2s is 7.4v which may be too high for your servo choice.
Looked up and seems they handle up to 7.2v so wack a 20A diode in series with the lipo.
1 Like
2S lifepo4 would be 6.4V
ManiaX LiFePO4 2S 3800mAh 6,6V RX 25C - The ManiaX Power LiFePO4 Batteries are not power enough.