In dual battery setup, a DC DC charger allows you to charge an auxiliary battery from the alternator whilst driving. With the DC DC charger, the main battery remains unaffected and always ready to start the car. And the DC DC charger can activate lower input voltage operation to suit vehicles with smart alternators.This 12V DC DC battery charger can utilize a solar panel or a starting battery linked to the alternator, while giving the priority to a solar input to place less load on the alternator. The DC to DC charger is suitable for LiFePO4 and lead acid: AGM, gel & calcium batteries, and allows you to re-select the battery during charging. With the memory function of this battery to battery charger, you dont need to re-select the same battery type every time. And 6-stage charging is engineered for better maintenance & longer lifespan of battery. If youre planning an off-grid camping, this 40A DC DC battery charger will be your perfect companion for a dual battery setup.