In my opinion--your last post suggests you are not on board with the likely root causes being provided by this thread. My early 03 [late o2] Alpine has/had the inverter on a shelf in the small compartment just in front of the passenger side rear wheel well. The echo charge is a relatively small electronic device on the ceiling, near the inverter. Point is--its not comparable with a typical bat charger--very modest rate of charge. On the road, your battery isolator routes charge from the alternator to the bat banks. While on shore power or genny--the inverter provides the charge to house bats. The echo charger has little if any impact on the bat while driving; while on shore power, it transfers a modest amount of charge from the house to the chassis bat based on the the house bats being at a high state of charge. Again, think you should focus on the alternator, the battery isolator, and your battery banks [bats and connections].....
2003 40' MDTS
Garden Ridge, Texas