Motors seem to have different power on USB vs Battery Pack

I have this setup for an obstacle avoiding robot. When I run the sketch with the usb cable connected to the Arduino, it seems to run fine. But when I move over to the 9V battery pack, it seems to run slower and not at all as expected.

Shouldnt it have more power to run on from a 9V battery pack? I guess it depends more on the mA than on the V, but I was wondering if this is a common issue and is solved in some other way?


Here is a video of it. The first half has the engine working with the usb cable and the second half is off the 9v. You must let the whole video load before playing it or else both halves look just as slow :slight_smile:


Here is the sketch just in caseā€¦

obstacleavoidingrobot.txt (10.1 KB)

Alas neither power sources are appropriate - with USB you risk damaging your Arduino or computer,
with the motor powered direct from a battery it has to be a battery capable of high current, and small
9V batteries just can't provide anything like enough current.

Separate high current battery pack for the motor driver is the safe and reliable approach.

So you're saying I should run the arduino board from the 9v but the motor shield from a high current battery pack? Such as a LiPo?

Yes, although a 9V battery isn't really adequate for an Arduino, which draws 35mA or so... 9V
batteries are for low power only.

Ok great, thanks for the help...ill charge up a LiPo. I also have a wall connector that outputs 5v. Im just not sure how to get the power from it without cutting up the cables which I wouldnt want to do.

Here is a video of it.

Marciokoko, didn't you get the memo about vertical videos? In case it's not clear, here's another one.

I generally use LiPo packs for robots. I get a lot of my stuff from HobbyKing. I think they have pretty good prices on LiPo batteries.

If you need to reduce the voltage from a LiPo or other battery pack to power a servo (or camera), you can use these inexpensive regulators.

Those little 9V batteries cause all sorts of problems. The belong in smoke detectors, not robots.

Hahahaha! Thanks, Ill keep that in mind next time.

Ah man, I just got some step UP transformers...

I guess Ill have to get step down as well.


Ah man, I just got some step UP transformers...

Single cell LiPo chargers are so inexpensive, I've been really wondering about using a single cell LiPo in some of my projects. I have a bunch of those 5V step up regulators and single cell LiPo chargers but I haven't used them with robotic projects yet. I hope they work well.

Tomorrow I'll charge up the lipos and use them to power both the camera and the robot.

Where can I get a nmh battery pack? I understand those are the best for motor applications.