H BRIDGE reducing power

Hello everyone. Noob question here. I have a H Bridge hooked to a 9,6v battery. The battery is hooked to the vc pin of the bridge and the control pins hooked correctly to the arduino. Arduino is powered separately. The 9.6 battery is powering two 9v motors. GND is shared in the arduino. When I power the arduino the code is making the motors move correctly forward and backwards. My problem is that if I connect the battery directly to the motors, they spin with much more torque than when I plugged them into the H Bridge. I'm not using any resistors or anything else other than the H bridge and the arduino. Am I missing something? BTW the H BRIDGE is a L293D. Should I be using a different bridge?

The L293D is darlington based, so you lose 2.5V immediately, perhaps even more if
pulling a lot of current. A MOSFET bridge would behave much better.

How much current do the motors need? Are you overloading the L293D's current
capabilities anyway?

I took both of them out of an old RC car. They’re 9 volts each. So if the L293D reduces voltage I should be ok if I hook a 12 volt battery pack instead? L293D max is 12v I believe.

Only if you're sure the current taken by the motors is less than the max the L293D can
handle, otherwise no.

Why not explain what motors you have? We can't guess these details!

Thank you Mark. Sorry, I can't explain more. I'm new to this. I know they're 9volts because they look like the ones I purchased at Radio Shack. Other than that, I don't know. The ones from Radio Shack say: 9-18VDC motor, 11000 to 24000RPM operates 9,12,18VDC input.

I know they're 9volts because they look like the ones I purchased at Radio Shack.

That is probably a poor assumption. Years ago i got a 12v motor from radio shack and it would probably smoke a L293D. You might want to get a larger H-bridge like below. You could measure the loaded current using a multimeter in series with the motor and battery.

Hi ldelvecchio,
It's all been said before regarding the L293, yes you lose power, so use motors rated at 3-6v, or replace the L293 with an SN754410, which performs better and is pin compatable with the L293. Or better still used something like the DRV8833 this is a FET based driver, avaialable as a chip or small module, much more power....

Regards

Mel.

ldelvecchio:
Thank you Mark. Sorry, I can't explain more. I'm new to this. I know they're 9volts because they look like the ones I purchased at Radio Shack. Other than that, I don't know. The ones from Radio Shack say: 9-18VDC motor, 11000 to 24000RPM operates 9,12,18VDC input.

Looking like implies nothing about voltage - that depends on what its wound for.

You can measure the stall current for a given voltage, and you can estimate the power
rating from the basic size of the motor...