big three

Sure can, and probably is. Charging is easy if you use something like ... (from another recent on-site OldFart reply) The aux battery would be your yellow-top in the trunk. (Enclosed batteries MUST be sealed else vented to the outside.) It is only connected to the alternator (and engine-bay battery) when the alternator is charging. Otherwise it is independent, hence NOT draining your engine-bay battery. The "charge lamp terminal" (aka circuit) could be any "over voltage" sensing circuit. The aux relay as shown will probably have to drive another relay that is rated to carry at least your alternator current (instead of itself being that "heavy" relay). This assumes limited current sourcing capability from the voltage sensing or charge-lamp circuit. The circuit shown has been used on 1980s - 1990s Bosch & Hitachi 2-wire alternators (70-120A) which drive both the standard charge lamp (250mA) and the added 68-Ohm relay solenoid (~200mA) of the 60A Aux-relay. (I suspect similar alternators could sink/source up to 500mA, but that might be risky.) Anyhow, see what you think and we can develop the idea. With the AGM next to the Amps, you can sell your cap to fund a dash mounted voltmeter and maybe your next battery, or more cabling etc. Maybe even magnetic breakers that can also double as the heavy 200+ Amp relays (aka contactors). Ah yes - the ultimate zero-drop high current protection and control system. Fuses? Thermal breakers? How primitive!

haha i kinda get it im gonna try the 0awg first and mess around with some grounds.  if that dont work the optimas deffinitly goin in the back. Db electrical 200a alt

0awg wiring kit

Yellow top optima

2 pioneer premier TS30004DVC subs