# Blog

## APPROXIMATE CALCULATION OF BATTERY CAPACITY

23 Apr 2018

The most frequent question when designing any project using batteries relates to what features and benefits will be achieved in the final installation.  What is the capacity of this battery and what performance can be expected?

The answer can be found by looking at the number of Amp hours a battery has.

You can expect a 100 Ah battery to supply approximately:

• 20 A for 5 hrs = 100 Ah
• 25 A for 4 hrs = 100 Ah
• 33.3 A for 3 hrs = 100 Ah
• 50 A for 2 hrs = 100 Ah

While this calculation is quite useful for providing a reference of battery capacity, it is not exact because:

• The efficiency of recovering energy accumulated in a battery will depend on the rate of discharge. That is, a battery discharged over 100 hours will have greater capacity than one discharged rapidly in 1 hour.
• In practice, a battery discharge is never at a constant intensity, as even with constant power consumption, voltage Drops as current increases.
• The final discharge voltage has not been considered.
• We have not taken into account various calculation coefficients – design, age, temperature etc.

Rodrigo Suárez Cueto