🔋🔥 Contrary to common belief, Lithium-ion batteries’ fires are most commonly due to cell imbalance issues.
Cell imbalance is the dispersion of cells (or strings of cells) associated in series. This phenomenon could stem from various parameters, such as resistance, SOC or SOH. It is supposed to be compensated most of the time by the BMS balancing system. Unfortunately, the the cells’ imbalance can increase to a level for which the cell balancing performed by the BMS is no longer effective.
This is why an accurate and predictive monitoring of such indicators is a must!
ΔR – Cell imbalance du to internal resistance dispersion
Such imbalance leads mainly to a loss of the energy efficiency. It is all the way more recommended to replace the defective module as the BMS is not able to compensate such cell-imbalance.
ΔSOC – Cell imbalance due to State-of-Charge dispersion
This kind of cell imbalance is supposed to be compensated most of the time by the BMS cell balancing system. However, in some cases the BMS fails to detect or balance the cells properly.
It is hence highly recommended to follow the evolution of the imbalance, and to replace the defective module in case of persistent imbalance.
ΔQ – Cell imbalance due to State-of-Health dispersion
In this case, the imbalance involves a loss of useful capacity and can lead to over-charge / under-discharge the defective cell or string of cells, and consequently lead to safety risks.
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