The present disclosure relates to a dual energy storage system that includes a lithium ion battery electrically coupled in parallel with a lead acid battery, where the lithium ion battery and the lead-acid battery are electrically coupled to a vehicle bus, where the lithium ion battery open circuit voltage (OCV) partially matches the lead-acid battery OCV such that the lead-acid battery OCV at 100% of the lead-acid battery state of charge (SOC) is about equal to the lithium ion battery OCV at 50% of the lithium ion battery SOC.