2 battery system with smart alternator

[wolfyjy]

just got a new van, has a 185A smart alternator and 92A AGM battery. I want to replace that battery with  twin 105A AGM batteries but there are 2 schools of thought on this. one idea is to have both batteries identical in every way including age and wire them in parallel but some people say this introduces extra resistance which the smart alternator won't like. the other way is to get a dc to dc charger installed between the batteries. if i go down the 2nd route what size charger do i need if my 3 power amps draw 100A from the 2nd battery

[SnowDrifter]

iirc most 'smart' alternators use 2 metrics: Voltage, and current, with current being measured through a ground clamp (not a literal clamp. It's a loop that measures magnetic field and infers current)

You could get around the ground clamp by either:
- Passing the ground wires for the batteries through the ground clamp
- Wiring the batteries in parallel to echother directly. Secondary battery has no other connections. Ground clamp still used, but might make wire fitment easier


Though.... More details on your end goals would be helpful