What is the normal balance for an account payable?

There is no way to find out! But to help managers to take prudent decisions in their businesses is crucial the knowledge of financial state of the company which can be measured comparing current liabilities vs current assets (Income Statement). At no time the balance should be negative. If so, the company owes more than it produces. Good to recall that all expenses during the period is in accordance with the budget. Additional expenses should be revised first in the budget before authorisation - focusing always in saving costs.