By what percentage must over-current devices protect batteries against excessive load current?

The correct percentage range for over-current devices to protect batteries against excessive load current is typically aligned with the significant fluctuation in power draw that batteries can experience. When the over-current protection is set at 150 to 250 percent of the battery's rated current, it allows the batteries to handle short-term surges in load without tripping the protection. This range is designed to safeguard the batteries while accommodating the startup currents and transient loads that might occur during operation, which are often much higher than the continuous rated load current.

Setting the protection too low could result in frequent trips of the protective devices during normal operations where temporary overloads might be encountered. Conversely, setting it too high could risk damage to the batteries from prolonged exposure to overload conditions.

Other ranges provided are either too narrow or too high, which may not align with standard practices for protecting batteries effectively during transient conditions while ensuring safety and operational integrity.