Please note that I am not licensed to practice law in the state of California. It is difficult to predict what penalties you would be facing for domestic violence. Typically, penalties include jail time, anger management, batterer's assessment/treatment counseling programs and fines. I strongly recommend that you contact a criminal defense attorney in your local area.
In California, the law penalizes more harshly for someone who picks up a 2nd domestic violence conviction within 7 years of a first domestic violence conviction. There are different ways that domestic violence can be charged (generally either as a 243 or a 273.5). However, a second time offender with a prior 273.5 charge faces up to 5 years in state prison. Of course, depending on the circumstances, and the alleged injuries, a good defense attorney may be able to negotiate for the charge to be reduced from a felony to a misdemeanor, and for the person to do an alternative to state prison such as CALTRANS, electronic monitoring, or county jail time (as opposed to state prison.) California takes domestic violence cases very seriously, and you should consider retaining a private attorney to handle this matter.