Stocks strengthened in mixed volume going into the final hour of trading Wednesday. The Nasdaq and the Dow Jones industrial average each rose 0.5%, while the S&P 500 gained 0.6%. Volume was tracking higher on the NYSE and lighter on the Nasdaq in the stock market today. Tesla Motors (TSLA) rose more than 5%. The company said in an email to analysts and investors it will unveil a home battery and a “very large” utility-scale battery April 30.