Deep discharge generally refers to the discharge of approximately 80% of  the rated capacity of a battery. After a period of use, there will inevitably be some active substances sinking in the power UPS power battery. If the active  substances are not activated in a timely manner, it will inevitably have some  impact on the capacity of the battery. Therefore, it is best to conduct a deep discharge of the battery every few months, which is beneficial for extending the  battery life. But avoid excessive deep discharge, otherwise it may cause  damage to the battery.

During the discharge process of UPS power battery, lead dioxide and  sponge lead form small crystal blocks of lead sulfate in a chemical reaction.  After excessive discharge, lead sulfate will form many large crystal blocks.  When the crystal blocks are unevenly distributed, the electrode plate will  undergo irreversible warping, while increasing the internal resistance of the
electrode plate. During charging, the lead sulfate crystal blocks are difficult to  restore, hindering the progress of charging.

What are the reasons for excessive deep discharge of UPS  power supply batteries?
Most UPS power supplies have the highest efficiency at a load of 50% to  100%. When the load is below 50%, their efficiency drops sharply. Therefore,  when UPS operates excessively under light load, it is not cost-effective from  an economic perspective. In addition, some users always believe that the  lighter the load, the higher the reliability of machine operation and the lower the  failure rate. In fact, this concept is not comprehensive because the light load  can reduce the probability of damage to the final power transistor, but it is  extremely harmful to the battery. Due to excessive light load operation, if the
UPS power supply battery does not have a deep discharge protection system  after a power outage, it may cause excessive deep discharge of the battery,  causing permanent damage to the battery.

1. Long term low current discharge. As we all know, the capacity used by UPS  power batteries is closely related to the discharge current. The smaller the  discharge current, the more capacity is actually discharged. Generally  speaking, the discharge capacity of a battery must be controlled within 80% of  its rated capacity. That is to say, when the battery discharges 80% of its rated  capacity, it is not allowed to continue discharging. If discharge continues, it will  cause deep discharge of the UPS battery. If remedial measures are not taken  in a timely manner, it may cause permanent damage to the battery.

2. Long term frequent discharge. Some units and regions may experience  frequent discharge of UPS power batteries due to frequent power outages. If  there is not enough time to charge the battery after it is discharged, and the  second time it is discharged immediately, such a large number of times may  cause deep discharge of the battery. UPS all have a minimum voltage protection value for the battery, but the  terminal voltage of the battery is closely related to the size of the discharge
current. When the discharge current is small, the terminal voltage is high, and  the actual capacity released when the minimum protection value is reached is  more. Therefore, UPS operating under light load should try to avoid the
phenomenon of discharging to the lowest protection value before shutting  down. For UPS with long delay, the lower limit voltage protection value of  discharge should be appropriately increased.

How to prevent damage caused by excessive discharge of UPS  power supply batteries?

Batteries with a load discharged to a low battery state must be recharged  within 72 hours after discharge to avoid battery damage; When the UPS power supply is idle and not in use, the connected battery  should be disconnected, otherwise it may cause over discharge and damage  to the connected UPS battery within a few days to a week. Therefore, when  the UPS uninterruptible power supply is not used, the connection line between  the battery and the UPS power host should be disconnected

Battery manufacturers recommend that the UPS power battery should be  charged immediately after discharge. Recharging the UPS power battery as  much as possible within 72 hours after discharge will fully restore the battery's  capacity and lifespan. UPS power batteries do not allow the voltage of each  unit to be lower than 1V after battery discharge, which is 6V for 12V batteries; UPS usually designs an alarm. When the voltage drops to near the discharge  termination voltage (when a single 12V voltage is close to 10.8V), an alarm  sound will sound. At this time, the electrical appliances should be immediately  turned off and the UPS should be turned off. However, when the discharge  termination voltage is reached, it will automatically shut down to prevent over  discharge;

The requirements for cold and hot power in UPS power batteries are not high,  as long as they are at room temperature. If they are too high, they can easily  cause the battery temperature to rise, damage the battery performance, and if  they are too low, they can easily reduce the activity, leading to poor battery  acceptance ability and more charging and discharging times, indirectly  shortening the service life of electric vehicle batteries.

The above is the reason for excessive discharge of UPS power battery. UPS  power supply should avoid short circuit discharge or excessive deep discharge  of the UPS battery during daily use. Only accurate use of UPS can prolong the  service life of UPS power supply