Well, I have to say I've experienced some weird issues with a PolarCell battery I got from "wannsee-electronic" on eBay. At first it worked as fine as the OEM battery, but then my phone started disconnecting my 2G/3G connection. Was running Power Kernel and Thumb and at first thought it was the culprit. This mostly happened when I unlocked the phone and I started typing, few characters made through ssh before it "lost" the network/sim. Tried two different sim-cards, pushing the SIM down with piece of paper etc, nothing seemed to work. Found out that overclocking or underclocking seemed to help, it seemed to be worst at stock speed. It also cut the connection at times when I left the phone with keyboard open and pressed some key on it (and thus activating the keyboard backlight, with the screen still on). After a while the phone started locking, crashing, and finally it wouldn't even charge or boot most of the time. All this was fixed when I replaced the FAULTY BATTERY. So I'm not sure about the power regulator-theory (or then it also is bit faulty on... faulty batteries ), but it really seemed to be with some voltage irregularity caused by the battery.