LiPo INTERNAL RESISTANCE TESTING - a simple 12v load tester

Why do old, cheap, abused, and puffed batteries lack power? Voltage sag, which is a drop in voltage as the amperage draw is increased, such as when power is applied to a brushless motor. The main cause of this voltage sag is "internal resistance" which is the electrical resistance actually inside the battery itself.
The amperage draw of a circuit is determined mainly by the "load", which is the case of RC flying is the motor and other electronics. The power output in watts is determined by the amperage draw times the volts delivered by the battery. Most any fully charged LiPo battery will indicate its nominal voltage when checked prior to flying. The question is whether the voltage can keep up as additional amperage is drawn by the system.
One of the easiest and most objective ways of monitoring the health of a battery pack is to measure its internal resistance under a known set of circumstances and a constant load. The lower the internal resistance the better the battery will be able to keep the voltage up under stress. A battery that is old, puffed, crashed, overdischarged, etc. will have an increased internal resistance.
Link to shared version of the spreadsheet:
Open the link and select: File,download,(as Excel, or whatever format you work in) and download it to your computer. You may then overwrite the sample values seen there. Please don't make any changes on the shared file that is linked to as it might confuse future users who wish to download it.