This behavior is unusual, and often results from an old battery or a defective battery charger.
Try charging your SLA battery using a different charger and see if you notice any difference in performance. You can also go to a local battery store to have the charger and/or your battery tested. If you discover that the battery is worn out, it's important to replace the battery immediately. Operating a device using a worn out battery can be dangerous because of the potential for overheating or sudden battery failure.
When replacing an SLA battery, like the Casil CA1270... Make sure the voltage and dimensions of the new battery match the voltage and dimensions of the old battery. The Ah of the old battery doesn't necessarily have to match the Ah of the old battery exactly, however, you will discover that batteries with the same Ah capacity are about the same size. Sticking to the same battery dimensions will most likely lead you to a replacement battery with a similar Ah.
