This is what I got from Wiki:
1) Ampere-hours (A·h) is a measure of
electrical charge that a battery can deliver. This quantity is one indicator of the total amount of charge that a battery is able to store and deliver at its rated voltage. Its value is the product of the discharge current (in amperes), multiplied by the duration (in hours) for which this discharge current can be sustained by the battery. Generally, this value (or rating) varies widely with the duration of the discharge period (see:
Peukert's Law), therefore the value is typically only meaningful when the duration is specified. This rating is rarely stated for automotive batteries, except in Europe where it is required by law. Nominal capacity(A·h) by EN 60095-1 is rated at a fixed discharge current of I/20, within 20 hours until final discharge voltage of 10.5 V at 25 °C is reached.
2) Reserve capacity minutes (RCM), also referred to as
reserve capacity (RC), is a battery's ability to sustain a minimum stated electrical load; it is defined as the time (in minutes) that a lead-acid battery at 80 °F (27 °C) will continuously deliver 25 amperes before its voltage drops below 10.5 volts.
Ok, so what is the relationship between these two measurements? Reserve capacity is easy, but I'm not following them here at ALL:
Nominal capacity(A·h) by EN 60095-1 is rated at a fixed discharge current of I/20, within 20 hours until final discharge voltage of 10.5 V at 25 °C is reached.
What the hell are they saying? What do they mean by "I/20"???
Or should I just read your other thread?