The present disclosure discloses an in-vehicle detection system and power supply system and power supply controller, which relates to the power supply control field. The power supply system comprises a low-power generator; a battery pack for supplying power to the in-vehicle detection system; a charger electrically connected to the low-power generator and the battery pack, respectively; and a power supply controller electrically connected to the battery pack and the low-power generator, respectively. The present disclosure uses a low-power generator and a battery pack to substitute a high-power generator, which can reduce the requirement on a peak power of the generator by the in-vehicle detection system, and improve the efficiency of the power supply. In addition, since a low-power generator and a lithium battery pack are used to substitute the high-power generator, it is favorable to the lightweight design of the in-vehicle detection system, and meanwhile reduces noises and vibration, and is favorable to improving the user experience and performance metrics.