Equalizing charge is overcharging a flooded lead acid battery to counter sulfation and stratification. Sulfation is the process of accumulation of sulfate crystals at the lead plates when the battery is constantly undercharged. This has been discussed in detail in a previous post (Battery Sulfation).
If the specific gravity of the cells varies by 0.03 or more, you should apply equalization charge. Now, specific gravity measurements can be taken for flooded lead acid batteries only. So equalizing charge is ideally suited for such batteries only.
For this reason, an equalization system is necessary, mainly for both VRLA and lithium-ion batteries [1-4]. In any battery charging process, a solution to ensure a voltage balance or equalization of the charge is needed to restore balance or at least prevent it from developing .
Bulk, Absorption, and Float are the 3 main charging stages of a typical lead acid battery. In addition, there could be one more stage called equalizing charge. Bulk Charging Stage So, the first charging stage is bulk, in which the battery is typically less than 80% charged.
In most conventional battery charging practice, equalization is addressed either by driving the charge to a sufficient potential to assure some degree of overcharge for all cells, or with a separate higher-voltage charging step intended to reach the weakest cells.
Based on the cited problems, the equalization for the Lithium-based series-connected battery string is necessary in order to mainly keep the energy of the cells balanced and extend their lifetime , , , , , .