Is there a limit on the amount a lawyer can charge for a bankruptcy? Do additional charges have to be approved by the bankruptcy court?

It depends on which bankruptcy chapter you're talking about. The bankruptcy court has the power to approve or deny attorney's fees in any bankruptcy case.  But in a Chapter 7 case, there is no requirement to seek court approval for payment of the fees--but the fees MUST be disclosed to the court and the court can require disgorgement if found to be too high. In Chapter 13 or Chapter 11 cases, all attorneys fees must be approved by the court.