24V battery charger with LM723
For fully charging a 24V lead-acid you need almost 29V, and this topology cannot supply it.
On the other hand, remember this IC has two main Vref connections, one for Vo&lt;7V and one for Vo&gt;7V. So I think you naeed to change the connections, and I agree with earlier comments the Potentiometer connections could be interchanged in order to vary what N.I.input compares. 
My last remmark, is you're using a legacy IC meant for linear application as a switcher.