if you are experiencing horrid battery usage from your phone AFTER hacktivating it then goto this site and read this article
you can use a valid AT&T SIM card to activate the phone. I didnt have this problem when unlocking my friends phone. I had an old AT&T SIM in the phone so as soon as it was done unlocking, rebooting and opening iTunes the phone said activation complete and was done. When the phone doesn’t activate using the SIM it is constantly trying to activate via SIM so its draining your battery. Read the article about this fix.
Sorry, I have not applied this fix so I really can’t help anyone with it. I’d suggest asking the devs or other members from a forum. This is just up to help those looking for the battery fix. The fix is contained in Redsn0w 0.9.6 beta 6. download it free. Link is on the page I listed above.