Why Do the Voltage of LiFePO4 Batteries Drop Back

Lithium iron phosphate battery （LiFePO4 battery） as a rechargeable lithium-ion battery, has been widely concerned by friends in the industry, especially in the field of new energy vehicles are getting more and more attention. Read on, here we will learn about what is the reason for the voltage drop back of LiFePO4 batteries and how to find it.

The direction of finding the voltage fallback of LiFePO4 battery

Under normal circumstances, all the batteries’ voltages will fall down the fully charged after disconnection. Usually, the backed voltage is called "open-circuit voltage". The voltage that is fully charged to cut off is called "charge limit voltage", the rated voltage of LiFePO4 single cell is 3.2V whose charge limit voltage is regarded at 3.6V.

Fig.1

Normal voltage drops back when finished fully charged. 

When the battery voltage falls back after a full charge, it is said to be normal as long as the value difference is not very large. If the drop sharply in a short time, the biggest possibility is the quality of the battery problems, the high internal resistance of the battery, and self-discharge.

The charger is unstable or mismatched.

In normal conditions, chargers of lithium-ion batteries are constant current charging, constant voltage charging, or constant current and voltage charging. If the charging is not enough, there will also occur an unnormal voltage-drop-back problem.

Store conditions

The power lever of storing Li-iron phosphate batteries will affect the voltage drop to the extent which is also affected by the storage time. If stored for a long time, for example, a year, that will certainly occur back down, because LiFePO4 batteries are self-discharged internally. LiFePO4 batteries are generally stored between 70%-80% power lever, in this value range is determined to be the most suitable.

In addition, it is recommended that if the storage time reaches about six months, it is best to do charge and discharge management. With a protection plate, it is recommended to shorten the time to 3 months for a charge and discharge, because the protection plate has power consumption, which will be a little faster than normal.

There are two other reasons

The first thing to consider is the length of use of LFP battery cells, if used for too long, it will lead to a decline in the electrocution function, which is the case of life decay. Then look at the size of the load the battery is subjected to, and whether it matches. Finally, check whether your circuit system has problems such as leakage of external causes.

Fig.2

What is the reason for the voltage drop in LFP batteries?

●Because the load current is large, the lithium iron phosphate battery discharge function does not work, it will cause the fallback phenomenon

●Because the aging of LiFePO4 batteries leads to low battery capacity when the fallback occurs.

I believe that through the above introduction you have a basic knowledge of the causes of lithium iron phosphate battery voltage fallback.