2 6v batteries is a minimum of 208 AH capacity. If one only needs 150AH house battery capacity, then the trojan T-1275 is a true deep cycle 12v battery. It is one of the ONLY true deep cycle 12v flooded batteries available, but in general the 2 6v golf cart batteries are the best bang for the buck. One needs to factor in their greater height, about 11.5 inches tall.
If one only has 10 inches height or so, then one is stuck with the 12v marine batteries of group 24/27/29/31 sizes which are not true deep cycle batteries, despite the sticker proudly claiming otherwise.
http://www.pbase.com/mainecruising/deep_cycle_battery
I would go separate inverter and charging source, unless one has big bucks to spend.
While ONE big inverter to cover big loads sounds easiest, COnsider 2 inverters, One big one for the big loads and one smaller one for very light loads. A big inverter powering a light load is much less efficient than a small inverter powering a small load.
I have a 800 watt MSW inverter, and a 400 watt PSW inverter, but rarely use either, and use the 400 watt one more.
I still prefer manual control of connecting house battery to alternator, and use a 1/2/both/Off Switch, Blueseas 6007m. But as fas as any automatic choices in this arean go, i would use a high quality Solenoid, and have an additional illuminated switch on my dashboard to have the option of disengaging it with the engine running.
https://www.amazon.com/Cole-Hersee-...=cole+hersee+continuous+duty+solenoid+200+amp
If the thought of tapping a vehicle circuit to trigger the solenoid automatically was too mind boggling to conceive, i would use a voltage sensing solenoid, like this:
http://www.allbatterysalesandservice.com/browse.cfm/4,4018.html
IF a voltage sensing solenoid is the choice, I would get a 'Single sense' or a Unidirectional solenoid, as opposed to Dual sense, or Bidirectional.
My reasoning is My engine battery would always be fully charged. i would not want the voltage sensing solenoid to see the higher voltage caused by the solar cvharging the house battery, and then parallel the batteries. i would much rather have ALL solar wattage flowing into house battery, not sharing it with the engine battery.
Also the solenoid will require some amount of Solar wattage to be held closed, and I would rather this Solar wattage also go into depleted house battery.
While a fully charged engine battery will not accept much current, it will still consume about 10 watts to be held at 13.6v and perhaps 1.5 amps at 14.7v. Again these amp i would prefer to go into onluy the depleted house battery.
Some who DO lightly cycle the engine battery might find the Dual sense desirable, especially if they have a lot of solar excess. it is a personal preference which strategy one chooses reagrding sngle/dual sense, when solar is involved.
And Much of my personal preferences typed above, are not really applicable anymore as I only have one battery for house and engine anyway, but at some point when that battery is nearing the end of its life, I will get another battery and go back to Manually turning my 1/2/both/Off switch as needed.
One thing to note with the 1/2/both/off switch, is to NOT turn it OFF with engine running. Doing so could Blow the Diodes in the alternator, and likely will if the alternator was feeding a hungry depleted battery at the time.
Some of these 1/2/both/Off have an Alternator Field Disconnect built in, to prevent a load dump from frying the Diodes, but this requires an External regulated alternator to work and the field wires to be touted through the AFD terminals on the switch, and adapting this AFD to some vehicles would prove difficult or laborious or simply impossible, and hopefully not all three in that order.
