How long will a 1500mAh battery last with a 5 amp load?

Question

I am aware that a 1500mAh battery will last approximently 1 hour with a 1.5amp draw, 30 minutes with a 3 amp draw etc. What is the formula for calculating minuntes when I only have the amp load? Thankyou!

Answer 1

The relationship described provides a good estimate for low current draw.

For higher draws, you need to look at actual engineering data. Consider the AA cell datasheet:

http://data.energizer.com/PDFs/E91.pdf

The simpliest representation of a cell is a voltage source in series with an internal resistor. The internal resistance (IR) of a new AA cell (with a 2000 mA*hr capacity) is 150 to 300 mΩ, so with any external load at all, it will not generate 5A. With heavy draw, the IR rapidly increases, so even short circuited, it would only generate this kind of current for only a few seconds.  0.5A to maybe 1A is pretty much the limit for AA cells. More complex battery model better predict this type of behavior. Best was is just to use the datasheet, or ultimately, to test it yourself.

Best bet is to use a bigger battery, or a super cap, which is happy to discharge fairly quickly, though it only holds a little energy.

Answer 2

You already know the basic calculation, but batteries discharged at high rates do not have a linear behavior, and the behavior varies depending on chemistry and construction.

Often batteries are are rated at a 20hour discharge rate, so your battery would lats 20 hours at 75mA, but would last a little less than 10 hours at 150mA due to to various inefficiencies, and perhaps considerably less than 1 hour at 1.5A

A 1500mAh battery is not very large, depending on it's construction it might not be able to produce 5A at all due to internal resistance. If it can, it will probably be for considerably less than the18 minutes you'd get by simple calculation (1500mAh / 5000mA = 0.3hour)

If the manufacture of the battery publishes discharge curves you might be able to find the answer there., or else determine it by experiment.

Answer 3

1500 mA is the same thing as 1.5 amps.

The formula for this battery is

Time (hours) = 1.5 / draw (in amps)

Answer 4

Basically 1500mAh = 90000mAmin (1500 x 60)

Since 90000mAmin = 90Amin

Then for a 5amp draw the battery would last 90/5 = 18min

Answer 5

About 2 minutes less than you need.

OK, that's a snarky answer but the math behind this is very simple as the other people who answered presented.