So we all know (or should know) that when we have a battery die and replace it, we should "recalibrate" the new one, which involves wiping battery stats and a full drain from 100% to dead, and the like. We also know that this is a useful tool when upgrading from a 1500mAh to 1900mAh battery, and the like. We even know that when we flash a new ROM that we should wipe stats so the new ROM (which will handle the battery slightly different from low-level tweaks) will be more battery-efficient. All that said, it's very unclear to me (and some quick googling failed in helping provide additional information) as to what exactly wiping battery stats changes, and even where. The questions that I would love to have solid answers to: Where do battery stats exist? In the phone or in some memory chip in the battery itself? Are battery stats battery-dependent? If stored in the phone, where at? (Specifically wanting to know if installing a new ROM that formats /system/ will wipe them by the format or is it somewhere else?) If I have "calibrated" a 1500mAh battery and a 2000mAh battery, do I need to wipe stats when I switch back and forth between the two? If I have "calibrated" two different identical 1500mAh batteries, do I need to wipe stats when I swap back and forth between the two? Just looking for more understanding around what's happening behind the scenes here.