Are Battery Combiners That Same as DC to DC Converters?

Question:

I have installed an ACR on my boat. I bought two Lithium Ion batteries and was told I could hook them up and go. Then I was sold a DC To DC converter. I need help wiring this. I would really like to leave my ACR hooked up and wire in the DC to DC converter through the ACR? Sure would like to use my lithium batteries?  - Darren

Answer:

Battery combiners (ACR) and DC to DC charging converters are similar but different. The battery combiners are mostly bidirectional and share a charging voltage with another battery. The DC to DC charging converter is directional (one battery to another and not vice versa) and also modifies the output voltage like a 3 stage battery charger whenever there is a charging voltage at the input of the DC to DC converter.

Based on the above, select the device that best suits your design.