The board of India Cements Ltd has approved a fund raising through various instruments including convertible debentures and equity warrants, the company said Friday.   In a filing with the Bombay Stock Exchange, the company said it plans to raise up to $25 million through a convertible bond issue, with the bonds to be convertible at INR125 a share at the end of 18 months from the issue date.   India Cements, which is one of the largest cement makers in south India, said it will also issue secured debentures to raise $91.84 million.   In addition, its board has approved the issue of 29.6 million equity warrants to raise up to INR13.91 billion. The warrants will be convertible into equity shares within 18 months, the company said.  The company didn’t say how it will use the funds.