( If you rename otacerts.zip, it doesn't prevent the over the air update from downloading - it just prevents the complete downloaded file from passing the security test. If the download doesn't pass the security test, it simply tries again. Over and over and over again, downloading a 15MB file, destroying your battery life.
The solution is to allow it to download, and even allow it to install. It will copy the downloaded file to /sdcard/update.zip, reboot into recovery and attempt to automatically install it. Luckily, SPRecovery now blocks update.zip installs by default. Just allowing it to ATTEMPT to install the OTA update is enough to make it stop downloading over and over again. As you can see by my battery graph, as soon as I was able to make it stop trying to update, the battery usage leveled off.)
I don't know why users did it that way. I just delete SytemUpdater.apk, an that always seem to work for me.