Before testing, the battery must be fully charged at the correct voltage. Quiescent and alarm currents are measured in the battery lead with mains off. The battery must hold the system in quiescent condition for the required standby time and then run two worst-case alarm zones for the required alarm time, with allowance for ageing: required 20-hour capacity equals L times the sum of quiescent current times standby time and a de-rating factor times alarm current times alarm time, where the de-rating factor may be taken as 2 and the ageing factor L is 1.25 for a new battery, or 1.1 for a used one that still has to serve at least another 12 months (so a new battery is at least 125% of the calculated need); outside 15 to 30 degrees C the maker's temperature compensation applies. The condition test for a 24 V set: discharge at 0.8 times the C20 rating in amperes (a 100 Ah battery at 80 A, less quiescent current if left connected), record the load, isolate mains if testing in circuit, apply the load for 25 minutes or until terminal voltage falls to 21 V; a battery still above 21 V at 25 minutes passes, with the final voltage recorded; then restore charging. Batteries should be charged at least a week before any depleting test, damaged batteries replaced rather than tested, and a whole set replaced if one fails. The test shows whether capacity has fallen by more than 20%.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.