Thanks for the detailed answer @BLUETTI - I understand now. 
I decided to add an EB240 instead for various reasons and am very happy with the result. But I do plan at some stage to add even more capacity with the B300, and a D050S so this is all very good to know.
So how do you use the EB240 with the AC200P? I am looking for something I could leave connected together permanently to increase battery capacity.
Hey @markieboy711, I’m running a test right now with the AC200P car adapter connected to the EB240 12v car outlet. I’m running our refrigerator from the AC200P. The EB240 is supplying about 113w to the AC200P, which is pretty close to what the fridge is pulling from the AC200P.
So far, it looks like this could be a workable configuration. Come charging time, if AC isn’t available then there will need to be some re-plugging on the AC200, that’s all.
I’ll post back here if anything catches fire or gets weird.
[edit] nope, bad idea. see below…
So, chaining the AC200P from the EB240 via the DC Vehicle port turned out to be a bad idea. I can run our refrigerator more than 24 hours from the EB240 alone. After only 12 hours the EB240 is almost dead and the AC200P is at 69%.
The AC200P constantly shows about 110 watts going in constantly from the EB240 and the EB240 fan is running all the time. However the AC200P never charges from it, even with the AC turned off. It appears that 110 watts is doing … nothing.
So, bad idea. Glad I tested. Maybe someone else will chime in with an effective way to do what you’re looking for.
Yeah, I’m thinking this needs to use a D050S from a car adapter.
I don’t understand that. You can plug the AC200P into your car and it will charge. I wonder why you can’t do that with the outlet on an EB240 that is designed to run accessories that … can be plugged into a car outlet?
@eric102 I had not considered this configuration for my AC200P. I was wanting the new features of the 200MAX but really need affordable watts at this time. How do you use the EB240, AC output to AC200P AC input? If so how long take to charge AC200(P) if u have tested that (as opposed to simultaneous charge/discharge)? I need to see how many watts can expect fr eb240 (frankly I never considered as a battery ‘expansion’). Need to compare to b230 as well (overall weight is an issue as I age gracefully…or not so gracefully 
Oops just saw @number37 post…I need to look into this more but sure sounded like a nice option. Want to understand all the pros/cons.
That seems strange. Good observations to consider, anyone else tested their eb240 as source of additional/ backup watts for AC200/P?
@PaulL71 interesting. I love seeing all the different configurations people are using w/ their bluetti products and their reasoning. I wonder if same would b true of the eb240 (< watts used by inverter) in this type configuration. My goal right now is more watts storage but also to have sogens different locations to minimize cords and hauling (kitchen, bedroom and basement (furnace).
I don’t have the EB240 but with my EB150 I get an additional 900wh of usable power from the AC200P when charging it via the EB150’s AC inverter. Since the EB150 normally produces around 1,200wh of usable power on it’s own that means I’m losing about 25% passing it through the AC200P rather than using each unit individually.
That’s fine for me since I only needed around 500wh on top of the AC200P’s output to get me through a night running two household size fridges and a gas furnace during a power outage. The gas gen or solar can take over during the day.
I’m wondering how efficient the B230 or B300 batteries will be connected to the AC200P? Hopefully at bit better 
Thx @eric102 I’m planning to use ac200p for powering furnace also during power outages. Curious how you are implementing that. I had an outlet added to grid off switch box when new furnace installed. When I flip switch at furnace off I plan to plug in extention cord (12ga) from bluetti. I haven’t tested yet but soon. Cheers
Through a generator transfer switch.
You can also use wire it into your main panel with a back-feed breaker and lockout switch to disconnect the panel from the grid while the AC200 backfeed is on. I did this with my jackery 1500 and it works. The power back won’t support all your loads, so you will have to be selective which breaker you turn on.
