Batteries that are not used for a long time will discharge on their own and may be susceptible to sulfation. If such batteries are charged with a quick charger, they do not accept the charging current and, due to the so-called surface charging, become "complete" too early. They are faulty.
1. Before rejecting a battery, check it.
2. Check electrolyte density. If the density in all banks differs by no more than 0.04 g / ml, the battery should be charged with a normal charger.
3. Check the battery after charging under load. If the values are not correct, the battery is bad.
4. If the density of the electrolyte in one or more banks is significantly lower than in the rest (for example, in 5 jars the density is 1.16 g / ml, and in one 1.08 g / ml), the battery has a short circuit.
5. To avoid premature battery aging, recharge the stored battery every 2 months.