12v 6000 watt inverter charging settings

Not necessarily.  Just set the charge voltages to what you'd like them to be (slightly dependent on the battery spec sheet).  "Charge Amps" percentage is such because I haven't worked out a conversion calibration for that (i.e. "battery amps").  If you happen to have a DC clamp ammeter, that makes measuring charge current very easy.  Otherwise, the likely limit will be the AC input...if it's a 120v AC input to the inverter, that's going to limit your maximum charge.

If you're already running a 240A alternator into the batteries, I don't think there's anything the inverter can do that will exceed that 😉.

The only thing the inverter does NOT have for lead-acid batteries is temperature-based voltage compensation.  But if your batteries are sorta climate controlled, this should not be a problem.

Induction cooktop should be an easy load for the inverter to handle...it isn't a surge load.

Let us know how the inverter handles/behaves @ 12v 😉.

I'll let you know....the charge function is only to save wear and tear on the engine/alt....during my time off with it parked in my yard it would be mostly just a expensive "maintainer" as the batteries are 364 bucks each and typically last 3 years.

Umm....

...how many Ah are these batteries rated for each?

For such a short lifetime, you MIGHT have a pretty quick payback with LiFePo4 cells.  Boy I don't miss lead-acid one bit...

If you want to hold a steady "float SOC" with the inverter, that's pretty easy to configure (especially if you want it to charge ALWAYS when AC is applied). 

Alternatively, you could configure the inverter to "start charge" at a certain voltage...then set the "Absorb Tmr." to "Charge Off" to stop charge when the desired voltage has been reached.  It would then automatically cycle charge on/off based on the battery voltage.  I might be overthinking it though 😉

Well sound slike he useing the same type of batts I used on my 24ft box truck and they are 31 group I thing they are rated over 100ah  which I'm getting roughly 170ah with my setup of 24v with two set of the batts in question and a set of agm batt.  Since lead only give you roughly 50% of so called rated amp hour.   As long as he don't push over 300A he should be good, pulling 600a to max out that inverter with only 3 of thos batts would be a bad deal. bet the wire isn't even 0/2 or 0/3 awg cables like what I used.

Looks to me like the default charge settings are pretty suitable for battery tending. You could make the float value match what your alternator outputs when the battery is fully charged.

For 364$ you can buy 12v 100AH LiFePO4's. 650 gets you 200AH. Delivered. You can get them even cheaper in the lower 48 from AliExpress.
That said, Semi probably exposed to cold climate... severely complicates matters - or doubles [or more] the battery cost for self-heating ones.

Just a quick update. The inverter arrive and after several months I finally installed it into the truck. Still have yet to wire up a plug to plug it into an extension cord but I have the waterproof plug for it now. Running it off of 4/0 cables that are around 12 feet long so I should have enough current carrying ability as the largest thing I power is a 1500 watt induction cooktop. It does pull the batteries down to 12.2 after a bit of use but the trucks voltmeter still shows 13.5 volts engine running....the issue I thing is the cables that join them together. I think they're only rated at 100 amps. I'm thinking of changing over to a copper bus bar instead of cables to connect them together.

These are in an automotive use setting so I don't think LiFePO is an option as it's being charged by an alternator at 13.8-14.2 volt output. Also I thought that LiFePO batteries were temperature limited. I use them in temperature extremes of -30F to +120F also.

They are 105AH deep cycle batteries. I use an ultra capacitor as the starting power source so I only have 3 lead acid batteries for a total of 315AH of capacity. I wish I could use the technology of lithium but unfortunately in my operation I cannot.

Thinking about the temperature issue for LiFePO..I could run heater lines, a heat exchanger(old heater core) and a 12v water pump into the battery box and use the engines latent heat to keep them above freezing fairly easily....something to think about.

120F is pretty hot.  Is that your ambient or is this in a confined space like the engine bay or other hot area?  lifepo4 will live at that temperature but it won't be enjoying it.  Lead acid would be feeling it too.

They do have self-heating LiFePO4s. It's just that they are much more expensive. (almost double...)

An example:
https://www.amazon.com/CHINS-LiFePO4-Battery-Lithium-Built/dp/B09PD8H541

I don't really like them because they make a SOC shunt useless.

That would be a mid/late summer day in Texas/Arizona