Why does the battery eliminator connected to the wall provide a better spin to my dc motors than my battery of the same voltage? Using a H-bridge, I've connected my DC Motors to an Arduino. When I accept the external power source from a wall, using a 9V battery eliminator, the motors spin well and consistently. However, when I connect it to a 9V battery, the motors spin slower, and the speed deteriorates till the motors stop. This happens in approximately 5 minutes. I checked with multiple 9V batteries of the same type. I have tested the batteries to check if they're dead after the motors stop. They are not, and if I reconnect the motors to them, the same process occurs all over again. I have checked for short circuits, and there are none. Any possible ideas as to why this is happening?
First off, never use 9V batteries to power motors or any device that consumes more than a few hundreds mA. Those batteries are just too weak.

Now a battery eliminator is not a pure equivalent as it can typically supply 800 mA or more, depending on the model you get.

The only commonalities between the battery and the eliminator are the 9V voltage and the socket.

If you want to power DC motors with batteries then rather use several 1.5V batteries in series.