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Apr 21 2025In the application of lithium iron phosphate batteries, the nominal voltage determines whether it can be used, and the rated voltage determines how to use it.
In the technical parameters of lithium-ion batteries, "nominal voltage" and "rated voltage" are core indicators, but they are often misunderstood. This article takes the mainstream lithium iron phosphate battery as an example to clearly dismantle the difference between the two and explain their impact on practical applications.
1. Definition and core differences
(1) Nominal Voltage:
It is the "nominal operating voltage" of lithium iron phosphate batteries, which represents the average voltage of the battery under standard charge and discharge conditions. For example, the nominal voltage of a 3.2V lithium iron phosphate battery is 3.2V, corresponding to a discharge platform of about 2.5-3.6V.
Features: Used to identify battery systems (e.g. 3.2V corresponds to lithium iron phosphate, 3.7V corresponds to ternary lithium).
(2) Rated Voltage:
It is the "safety upper limit voltage" of the lithium iron phosphate battery, that is, the maximum allowable charging cut-off voltage. For example, the rated voltage of a 3.2V lithium iron phosphate battery is 3.65V. Exceeding this value may cause overcharging, heating, or even fire.
Features: Directly related to battery safety, requiring strict matching of the charger and battery management system (BMS).
To distinguish in one sentence:
The nominal voltage is the "working reference value" and the rated voltage is the "safety red line".
It is the "nominal operating voltage" of lithium iron phosphate batteries, which represents the average voltage of the battery under standard charge and discharge conditions. For example, the nominal voltage of a 3.2V lithium iron phosphate battery is 3.2V, corresponding to a discharge platform of about 2.5-3.6V.
Features: Used to identify battery systems (e.g. 3.2V corresponds to lithium iron phosphate, 3.7V corresponds to ternary lithium).
(2) Rated Voltage:
It is the "safety upper limit voltage" of the lithium iron phosphate battery, that is, the maximum allowable charging cut-off voltage. For example, the rated voltage of a 3.2V lithium iron phosphate battery is 3.65V. Exceeding this value may cause overcharging, heating, or even fire.
Features: Directly related to battery safety, requiring strict matching of the charger and battery management system (BMS).
To distinguish in one sentence:
The nominal voltage is the "working reference value" and the rated voltage is the "safety red line".
2. Practical application scenarios of lithium iron phosphate batteries
(1) Nominal voltage determines device compatibility
The nominal voltage of lithium-ion batteries directly affects the device power supply design. For example, a 3.2V lithium iron phosphate battery needs to be powered by a boost module (such as 3.2V→5V) to power a drone, while a 3.7V ternary lithium battery can be directly adapted to some devices. If the two are confused, the device may fail to start or performance may deteriorate.
(2) Rated voltage is related to charging safety
The rated voltage of lithium iron phosphate batteries must strictly match the charging strategy. For example, a lithium iron phosphate battery with a nominal voltage of 3.2V has a rated voltage of 3.65V. If a 4.2V charger (applicable to ternary lithium) is used, it will cause overcharging and failure. The nominal voltage of ternary lithium batteries is 3.7V and the rated voltage is 4.2V. The charging strategy needs to adapt to its chemical characteristics.
Lithium-ion battery parameter comparison:
The nominal voltage of lithium-ion batteries directly affects the device power supply design. For example, a 3.2V lithium iron phosphate battery needs to be powered by a boost module (such as 3.2V→5V) to power a drone, while a 3.7V ternary lithium battery can be directly adapted to some devices. If the two are confused, the device may fail to start or performance may deteriorate.
(2) Rated voltage is related to charging safety
The rated voltage of lithium iron phosphate batteries must strictly match the charging strategy. For example, a lithium iron phosphate battery with a nominal voltage of 3.2V has a rated voltage of 3.65V. If a 4.2V charger (applicable to ternary lithium) is used, it will cause overcharging and failure. The nominal voltage of ternary lithium batteries is 3.7V and the rated voltage is 4.2V. The charging strategy needs to adapt to its chemical characteristics.
Lithium-ion battery parameter comparison:
3. Why is it necessary to distinguish between the two types of lithium-ion batteries?
(1 )Risk of wrong selection:
If the nominal voltage is confused with the rated voltage, it may cause equipment damage (such as charging a 3.2V lithium iron phosphate battery with a 4.2V charger) or charging failure (such as not matching the rated voltage of the BMS).
(2) Basis for performance optimization:
The nominal voltage determines the series-parallel scheme of the battery pack (e.g. 3.2V batteries connected in series form a 6.4V system), while the rated voltage affects the overvoltage protection threshold of the BMS.
If the nominal voltage is confused with the rated voltage, it may cause equipment damage (such as charging a 3.2V lithium iron phosphate battery with a 4.2V charger) or charging failure (such as not matching the rated voltage of the BMS).
(2) Basis for performance optimization:
The nominal voltage determines the series-parallel scheme of the battery pack (e.g. 3.2V batteries connected in series form a 6.4V system), while the rated voltage affects the overvoltage protection threshold of the BMS.
