One of the main problems in Solar Inverter system is poor charging of Battery during rainy seasons and in cloudy days. The high current Tubular battery requires more than 1 Ampere current for proper charging. To solve this problem, I have designed a” Hybrid Solar charger” and the circuit was published in Electronics for You magazine September 2013 issue. So the charger has two sides. One side gets power from Solar panel and the other side from a Step-down transformer. If the voltage from Solar panel reduces below 9 volts, the charger shifts to AC mode and battery charges via the current from transformer.
You can see the working details of the circuit in the pdf file given. Normally the 12 volt 100 Ah Tubular battery will last around 5 years if the battery is properly charged and discharged. That means both the charging and discharging cycles maintain the life of battery. Otherwise, the cells of the battery becomes weak and Suphation occurs which damage the cells permanently. Suphation is the accumulation of Sulphur deposits on the lead plates, which prevents the release and acceptance of charge electrons. In ordinary Lead-Acid battery, this is very high but in Tubular battery it is less. Still it needs proper charging.
So the Hybrid Solar charger keeps the Inverter battery in top condition so that you can keep the battery unattended.
HYBRID SOLAR CHARGER