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Lithium Battery-school
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How does charging differ between LiFePO4 batteries and lead-acid batteries?

How does the charging process differ between LiFePO4 batteries and lead-acid batteries?

The charging process for LiFePO4 batteries and lead-acid batteries is different in several key ways.

LiFePO4 batteries are typically charged using a constant voltage charging method, where the voltage is held at a constant level until the current drops to a certain level. This helps to prevent overcharging and extend the life of the battery.

In contrast, lead-acid batteries are often charged using a constant current charging method, where the current is held at a constant level until the voltage reaches a certain level. This method is less precise and can result in overcharging and shorter battery life.

Additionally, LiFePO4 batteries have a higher charging voltage and require a special charging profile to avoid damaging the cells. Lead-acid batteries have a lower charging voltage and can be charged using a standard charging profile.

It’s also worth noting that LiFePO4 batteries are more tolerant to overcharging compared to lead-acid batteries, and they have a lower risk of sulfation, which is a common problem with lead-acid batteries.

What is the ideal voltage to charge lifepo4?

The ideal voltage to charge a LiFePO4 battery varies depending on the specific battery and the manufacturer’s specifications, but a typical voltage range is between 3.5V to 3.65V per cell. For a 12V LiFePO4 battery, the charging voltage should be between 14v and 14.4v

It’s important to follow the manufacturer’s recommended charging voltage and to use a charger specifically designed for LiFePO4 batteries, as charging a LiFePO4 battery with the wrong voltage or using an inappropriate charger can result in reduced performance and shorter battery life.

LiFePO4 batteries require a multi-stage charging process that includes a constant voltage charge and a topping charge. The constant voltage charge is applied until the current drops to a certain level, at which point a float charge is applied to bring the voltage to the maximum level. The multi-stage charging process helps to prevent overcharging and extend the life of the battery. The float charge is a stage in the charging process for LiFePO4 batteries that occurs after the main constant voltage charge stage. During the float charge, the voltage is held at a slightly lower level than the maximum voltage to prevent overcharging and to ensure that the battery stays fully charged. The float charge serves several purposes. First, it helps to balance the voltage between the cells in the battery, ensuring that all cells are charged to the same level. Second, it helps to prevent overcharging, which can reduce the overall life of the battery. Finally, it helps to maintain the battery in a fully charged state, ready for use when needed.

The exact voltage and duration of the float charge will depend on the specific battery and the manufacturer’s specifications. It’s important to follow the manufacturer’s recommendations to ensure that the battery is charged correctly and to maximize the performance and lifespan.

Lithium Battery-school
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LIFEPO4 – Internal Resistance, capacity, and its Performance

Cell capacity is of limited use if a battery pack cannot deliver the stored energy effectively; a battery also needs low internal resistance. Measured in milliohms (mΩ), resistance is extremely important the higher the C rate of the battery; the lower the resistance, the less restriction the pack encounters. This is especially important in heavy loads such as power tools and electric powertrains. High resistance causes the battery to heat up and the voltage to drop under load, this is bad for the cell, and the battery, this is what causes degradation and aging, loss of performance, and ultimately EOL(end of life)

A grade (what we now call Automotive Grade) LiFePo4 has a very low internal resistance and the battery responds well to high-current bursts that last for a few seconds to a few minutes (see the individual cell specification sheet). Compared to LFP Lead acid and inherent sluggishness, however, lead acid does not perform well on a sustained high current discharge; the battery soon gets tired and needs rest to recover. LFP however, suffers much less, And A-grade LFP is sorted by the factory because it meets the manufacturer’s specifications. This tells the manufacturer a lot about the cell, its expected performance, and its lifespan.

LFP is highly efficient and can have different performance characteristics

If we look at the A-grade EVE LF280 cells we can see the performance and efficiency. Very high!!!
Discharge capacity/nominal
capacity×100％

A）0.33CA ≥100％
B）0.5CA ≥98％
C）1CA ≥97％

We need to compare Lead Acid again for learning purposes, Some sluggishness is apparent in all batteries at different degrees but it is especially pronounced with lead acid. This hints that power delivery is not based on internal resistance alone but also on the responsiveness of the chemistry, as well as temperature. In this respect, nickel- and lithium-based technologies are more responsive than lead acid.

The internal resistance of Lithium-based batteries also increases with use and aging but improvements have been made with electrolyte additives to keep the buildup of films on the electrodes under control. With all batteries, SoC affects the internal resistance. Lithium has higher resistance at full charge and also at end of discharge with a low resistance area in the middle. This is important to note, as when you are caring for the cells, you can very simply make the judgment that keeping your Lithium cells inside the 80% window is going to minimise degradation.

The 10%-80%-10% rule for Lithium is a good one to follow. This means try to keep you cells between 10% and 90% State of Charge.

A look at the Manufacturing Process

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