Techniques to detect faults in a battery with at least two parallel battery cells. In some examples, a cell may fail or become disconnected. The circuitry of this disclosure may determine whether a battery pack has a fault by measuring battery parameters at the positive and negative terminals. When the circuitry detects a fault, the circuitry may adjust the charge rate so that the charge does not exceed the maximum charge rate of any single cell of the battery pack. In some examples, the circuitry may shut off the charge current to the battery pack to ensure that the charge rate does not exceed the maximum charge rate of any single cell. To avoid false positive fault detection, the circuitry of this disclosure may verify the detected fault and the parameters of the charging cycle before reducing the charging current.