All batteries progressively lose their store of energy even when not in use. This is why we should test idle secondary batteries regularly, and check the manufacturing dates on primary ones before purchasing them. Today we ask how do batteries self-discharge, and can we influence this process?
Batteries Self-Discharge Naturally When Idle
All batteries discharge when standing idle, although the rate varies. We can reduce this rate by keeping their voltage above the minimum level, and storing them in a cool place. That way, they should retain their capacity longer, and could have an extended lifespan.
A number of factors contribute to this self-discharge behavior, according to Neeraj Kumar Singal writing in LinkedIn. He includes chemical reactions, leakage, and temperature on his list, and suggests lower temperatures and special coatings as counter measures to reduce battery self-discharge.
Two Types of Self-Discharge – Chemical and Physical
Batteries definitely do self-discharge, although there are actually two mechanisms, namely chemical and physical processes behind this:
- Chemical discharge occurs when chemicals in a battery react with the electrolyte, producing unproductive elements. This electrochemical reaction reduces the voltage of a battery over time.
- Physical discharge leading to a reduction in battery voltage is the result of heat, vibration, or other mechanical action. Exposure to high heat accelerates this, because the ionic charge carriers move faster.
Testing to Measure Battery Self-Discharge Rates
Critical secondary batteries should be tested regularly to confirm their self-discharge rate over time. This information is useful input to understanding their capacity, reliability, and performance. However, active batteries inline do need to be disconnected from electrical circuits to achieve this.
The voltage in healthy batteries should decrease along a nominally straight line. However, a battery that does not follow this pattern will have a shorter lifespan than the norm. We can help reduce their self-discharge rate when we understand it, but we cannot prevent it completely.
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