Hybrid battery system

A method for power storage in a power network, the method comprising:

• receiving an operating voltage of power delivered to a load from a power source of a battery system including a first rechargeable battery unit and a second rechargeable battery unit having different battery chemistries;
• selectively charging and discharging the first rechargeable battery unit and the second rechargeable battery unit based on the operating voltage;
• and
• charging the first rechargeable battery unit and the second rechargeable battery unit at respective charge rates based on comparison of the operating voltage to a charge range and a first charge threshold.

A controller comprising one or more processors and non-transitory computer-readable storage media, the non-transitory computer-readable storage media having stored thereon instructions that, when executed by the one or more processors, cause the one or more processors to perform operations comprising:

• receiving, from a power supply voltage sensor, an operating voltage of power delivered to a load from a power source of a battery system including a first rechargeable battery unit and a second rechargeable battery unit having different battery chemistries;
• selectively charging and discharging the first rechargeable battery unit and the second rechargeable battery unit based on the operating voltage;
• and
• charging the first rechargeable battery unit and the second rechargeable battery unit at respective charge rates based on comparison of the operating voltage to a charge range and a first charge threshold.