Hello everyone.
I am building my first robot and am a noob at electronics, so need your help.

I'm looking for a charging circuit for a 12v Lead acid battery with 5v & 12v output. I mean to run 4 12v geared motors, run by an L293 H-bridge, and an arduino with it.

So do off the shelf standard circuits which can do this exist? If so, could you please list them. If not, where can I find directions to make one?

 

Separate the battery charging from powering the robot.

The H-bridge and motors can run directly from the 12V SLA (no regulation required). You will not be happy to learn that the L293 is very inefficient, and will only deliver ~9.7V to your 12V motor when powered with a battery whose terminal voltage is only 12.5V.

The Arduino will run just fine with 12Vdc from the battery going into the external DC input jack. The built-in voltage regulator on the Arduino will make the required 5Vdc. I am doing this in one of my projects.

A small 1A, microprocessor-controlled, three-step charging algorithm Sealed Lead Acid battery charger can be purchased for <$20. I wouldn't try to build one...