# High current power supply for servos? 40+ amps

#### kolleamm

Summary
high current power supply or battery
So I've basically built a robot that has a lot of servo motors. 14 of them can draw up to 3 amps each(max)(usually 1 amp average) at 4.8 to 7 volts.
What's my best option to power it? The power source doesn't need to be connected to the robot, so weight shouldn't be an issue.
My best guess is a car battery. Please let me know your suggestions.

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#### bobob

Find used sorenson power supply. They make lots of supplies that will fit your needs. Try ebay, but watch out for shipping costs.

#### berkeman

Mentor
Summary: high current power supply or battery

So I've basically built a robot that has a lot of servo motors. 14 of them can draw up to 3 amps each(max)(usually 1 amp average) at 4.8 to 7 volts.
Are you coordinating the multiple servo drives to minimize the total and peak currents required from the power supply?

#### jrmichler

Are all of the servos always driving, or are there situations where at least one is back driving and generating back to the power supply? If the friction is low, and inertia and acceleration are high, then you will have times when some motors are drawing power and others are generating power. This is a common situation in machines with servo motors.

If this is the case, then your power supply must handle two extreme cases:
1) The maximum number of motors are drawing the maximum amount of power.
2) The maximum number of motors are decelerating at their maximum rate. A typical case is when a fast stop of all axes is commanded.

Note that a motor with a reasonably efficient drive drawing 5 amps at six volts will pull 2.5 amps from a 12 volt supply.

Industrial servo drives with significant amounts of regenerated power and multiple motors will use a common DC buss. A single battery powering all motors counts as a common DC buss. A battery capable of powering all of the motors will absorb all of the regenerated power. So, yes, a car battery should make a good power supply. Be sure to check the drive specifications to make sure that they are designed for 12 volt input.

This assumes that you have four quadrant drives that can regenerate back to the power supply. Some drives just dissipate regenerated power into a resistor, in which case there is no power regenerated back to the power supply.

#### kolleamm

The amount of current needed is variable since each movement may be different, so I just assume the largest amount for each servo.

A sorenson power supply seems like a great idea.
I would like to use a car battery however the only problem is that the servos require voltages such as 4.8 , 6.0 , and 7.4, so I would need to adjust the voltage.

I have tried using voltage regulators in the past but the ones I bought from eBay didn't last very long (probably because they were poorly made).

If I could find a variable voltage regulator that could handle (30 amps at 7.4v) + (10 amps at 6.0v) ,then I could use a car battery.

Half the servos are also 4.8 - 6.0v and the other half are 6.0 - 7.4v, so I would need two power supplies.
I'm trying to accomplish all this within a couple hundred dollar budget if possible.

#### Tom.G

Half the servos are also 4.8 - 6.0v and the other half are 6.0 - 7.4v, so I would need two power supplies.
Use a 6V car battery, if you can still find them. Motorcycle or lawn mower batteries are another possibility.

"High current power supply for servos? 40+ amps"

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