Why doesn't the US fully support Li-NCM's as Toyota HEV replacement battery?
The Toyota/Lexus replacement battery made with Li-NCM battery has significant fuel-saving advantages & a clear price advantage over Ni-MH battery. It has gained widespread popularity and adoption in markets outside the United States.
However, in the US market, people are cautious in using it.
This is because Americans have an inherent spirit of seeking truth and rely on data-based conclusions. American engineers conducted some tests, based on which they concluded that using Dr. Prius app to test 28 Li-NCM batteries in a Prius, the highest voltage measured reached 249.29V.
This led to the inference that, on average, each cell had a voltage of 4.82V - 4.45V. However, the charging voltage limit for Li-NCM is only 4.2V. Therefore, there is a risk of overcharging the battery.
We believe that this conclusion is not entirely correct. Mainly because no matter 4.82V or 4.45V are peak volt and not continuous charging voltages. Therefore, inferring that there is a high chance of battery overcharging is incorrect.
As a solution provider and supplier of lithium-ion hybrid Battery Replacements, to confirm this, we specially added monitoring programs in the BMS. When the cell charging reaches 4.05V or above and lasts for 3 seconds, it lights up.
In March 2026, 20 Battery Modules with this special BMS were installed in a Prius C Car in Taiwan and driven on the highway for 4 days.
After removing the batteries on March 8th, it was found that only one of the 20 batteries lit up, indicating that this one battery had triggered a charging voltage of 4.05V or above for 3 seconds. While the other 19 performed good.
Therefore, our conclusion is that the voltage plateau of the Li-NCM battery, compared with the NiMH battery, although it has less remaining capacity, especially when compared with the 5S SIB and Lifepo4.
However, as long as the following conditions are met:
- The Li-NCM battery cells are brand-new and qualified A-grade cells.
- More importantly, the overcharge protection voltage parameter set in the BMS must be supported by numerus battery pack testing data.
The chance of overcharging is extremely low.
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