If a system draws 500mA, how long will a 7Ah battery approximately last?

To determine how long a 7Ah battery will last while supplying a constant current of 500mA, you need to first convert the 500mA to amp-hours for consistency in units. Since 1A is equal to 1000mA, 500mA is equivalent to 0.5A.

Next, you can use the formula that relates amp-hours (Ah), current in amps (A), and time in hours (h):

Time (h) = Battery Capacity (Ah) / Current (A)

Substituting the values into the formula gives:

Time = 7Ah / 0.5A = 14 hours.

This means that a 7Ah battery would last approximately 14 hours at a draw of 500mA. The answer reflects the correct conversion and application of the basic capacity formula for batteries, allowing for an understanding of how battery life is calculated based on current draw.