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FAQ: the voltage levels for LiFePO4 cells

15.Dec 2014

FAQ: the voltage levels for LiFePO4 cells

Question: I’m a bit confused about the charge and discharge voltage levels. I’m planning to use the LiFePO4 cells. I found the SBM Board on your page, but the deep discharge (over discharge) protection activates at 2.00V. In your email you wrote to me about 2.5V as a minimum for the LiFePO4 cell. However the datasheet for the LiFePO4 mentions 2.8V as minimum operational voltage. My question is: what is the correct voltage for discharge? The same question is for the overcharge voltages.

Answer: There is a difference between the general operation voltage levels, maximal operation voltage levels and the protection limits for the battery cells. The above diagram shows the examples of the voltage levels. Generally it is recommended to operate the LiFePO4 cells between 3.50V and 3.0V (also similar to values of 3.55 ~ 2.90V). The maximal change and discharge levels are 3.65V and 2.8V (2.5V under high current load). The SBM protection limits are set to 3.90V and 2.0V

As explained in another article, the SBM should be used only are the last protection resort. In most of the installations, the appliance equipment should be setup to work in the general recommended safe operation limits.

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