From the description of the problem, the battery should be at the end of its service life, the battery is seriously sulfated, the capacity attenuation is bad, you can try to repair it, if there is no effect, you can only change the battery. If the battery has passed the shelf life and the appearance is not damaged, swelling, no signs of short circuit, break, you can take the following methods to try to repair the battery: use positive and negative pulses to depolarize the battery, and then completely discharge, so cycle three times, if the capacity has signs of recovery, you can cycle several times to achieve better repair effect. Add water to repair, add water must add deionized water or pure water, do not add tap water, will cause the battery self-discharge big problem. The specific method is as follows: First discharge the battery completely, because the acid density inside the battery after discharge is basically less than 1.1g\/mL; Remove the cover sheet, and then remove the safety valve, pay attention to keep it well, do not dirty the safety valve, for later use; Add water, the general 12AH battery a single cell add water of 8 ~ 10g, 20AH battery a single cell add water of about 15g; Stand for about one hour, install the safety valve and cover; Charge, fully charge and then fully discharge, so the cycle of three times, the capacity will be good.