Jichai throttle

Your charging voltage is too low. The unit voltage of constant voltage charging should be between 2.3-2.5V If charging 2.3V, it can only be charged to a little more than 60% of the battery capacity. And your charging voltage is 27.2/12 = 2.267V. At this voltage, you can only charge 30-40% of the battery capacity. If the battery is in this state of charge for a long time, irreversible sulfation and damage will occur.