Check out the first "Quote" from the "Religion" theme for the other side of this, but "batter" is an interesting word choice. When you batter a gate or door, the whole point is to demolish it and make it useless for its intended purpose. On one hand, the word suggests that the speaker wants his heart completely destroyed, and on the other, he also suggests that his heart is designed to keep God out. But, could that be true? If God has created his heart, as the speaker surely believes, why would God design it to keep God out?
As yet but knock; breathe, shine, and seek to mend; That I may rise, and stand, o'erthrow me, and bend Your force, to break, blow, burn, and make me new. (lines 2-4)
Here's the best expression of the speaker's wish for brutal violence against him. The speaker wants God to "break, blow, burn" and "o'erthrow" instead of "knock; breathe, shine, and seek to mend." Fair enough – instead of being timid and curative, God should be violent and destructive. So, here's the key question: what does he actually want to happen? Does he really want his physical heart to be battered? Because that would be bad news.
So, one imagines the speaker is using a metaphor – he doesn't want to be physically broken, but does that mean that he wants his soul to be broken? That is, where should God direct all of this violence? If the answer is his soul, what does that mean? We don't have an answer, and that's in large part because it doesn't seem like the speaker has an answer either. He knows he wants some sort of reminder from God, but he doesn't quite know how to put it.
Take me to you, imprison me, for I Except you enthrall me, never shall be free, (lines 12-13)
Here, the speaker seems to bring back the castle siege metaphor one last time, but this is important to the violence theme, as it presents such an obvious contradiction. How God's imprisonment can lead to freedom is the same kind of question that we've been asking along: "Why does the speaker want God to be violent towards him?" This all reminds us again that violence and aggressive behavior aren't necessarily bad things in this poem, so long as it's God who does them.
Nor ever chaste, except you ravish me. (line 14)
Nothing too profound here, but we wanted to point out that "ravish" doesn't imply some simple friendly romp through the hay. "Ravish" implies that this sex (metaphorical or otherwise) is violent or aggressive.