Will the ripple on the charger's DC bus affect battery life? Detailed data analysis
There are also brothers in the group who mentioned the following hypothesis that the current backflow of the motor driver on the battery affects the battery more than the effect of charging on the battery. The motor driver in the electric vehicle reverses the battery current in three aspects. One is when the motor state changes, such as a sudden stop, etc.; the other is when the motor magnetic field is controlled, the current control algorithm is the FOC torque control mode, when the current or magnetic field When the vector changes suddenly; the third is every switching cycle, at this time there is an oscillating current on the DC bus, the lighter the load, the greater the oscillation. The distribution parameters of the battery and the resonance caused by some high-frequency components in the driver will exceed the high-frequency components themselves.
The battery has a large response difference with different SOC and frequency, and the iteration of the ripple mainly affects the battery in the frequency response.
This frequency response process is indeed worth thinking about
I initially found two data sources to provide this impact:
1) No impact in the short term (test at the battery system level)
Sven De Breucker did some experiments and tests in the article "Impact of Current Ripple on Li-ion Battery Ageing". This experiment is based on a 4-month short-term experiment
This research mainly affects the ripple current of the DC-DC converter and the aging effect of lithium-ion batteries, using two bidirectionally constructed dc-dc converters connected to two identical 12 kWh / 28 kW lithium-ion batteries.
One of the two battery packs is subject to higher ripple current, and the other is almost non-existent. At the end of each month
Pass the HPPC test to measure the battery parameters.
After doing it, the impact is basically not big
2) The long-term effect is not large (Twelve prismatic 28 Ah Li-ion cells with NCM111)
ALEXANDER BESSMAN did some experiments in "Interactions between battery and power electronics in an electric vehicle drivetrain"
This experiment went through a one-year test cycle, about 2000 cycles, and about 20% of the original capacity was lost. The amount of capacity attenuation has nothing to do with whether the ripple current (AC frequency) is superimposed
Summary: At this level, when the charger chooses GAN components, it will not have an impact on the life level of the battery cell when the higher frequency ripple is selected, and it will accelerate the development.
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