hi. i am very newby and want to be charging my ac200 max while towing and at the same time have it supply power to my refrigerator. Sure there must be an easy way. Sorry so uninformed…
Welcome to the forum @law !!
Lots of ways to get this to work for you man but going to need some information on your setup to advise the easiest/best solution…
I take it this is for your camper or rv then?? Do you have a 7-pin or auxiliary line ran already to your trailer for power?? If so, that would mean your car is already ran with a line to a converter which is charging up your trailers “house” batteries while towing.
This auxiliary line usually just “trickle charges” your camper house batteries while in transport. Meaning it doesn’t pull that much voltage from your car battery/alternator (usually like 14.1-14.6v?) but enough to DC charge while providing extra “juice” to run small appliances at the same time.
Is your fridge 3-way compatible? Does it run off 120v(AC), propane, and 12v(DC) power??
Simplest option would probably be to run your fridge off of your house batteries (12v/DC) power during transport, and simply connect your AC200 Max into your cars cigarette port.
If this is a portable fridge and is in your tow vehicle, you can simply connect it to the AC200 max, as the unit supports pass thru charging. I usually can input about 100w from my outback’s cigarette 12v port so it’s enough to power my fridge (65w full compressor engaged) while trickle input charging my unit as well.
To get more wattage/charging into your ac200max, you’ll need to charge via your AC input and this will require more draw on your batteries/alternator and additional wiring.
Hi, thank you very much Mr. Briney for answering.
Yes, we do have 7-pin connector at the hitch.
Yes, the refer is 3-way compatible AC/DC/propane.
My intended setup is to replace my camper trailer’s SLA battery with the Bluetti (AC200P or Max) riding inside of the trailer, while I drive, charging it with the 12VDC from the 7-pin connector/alternator power.
So, can i wire that 12VDC alternator power directly to an aviation plug and plug it into the Bluetti to charge it while it powers our 12VDC fridge at the same time, while we tow?
Or, will I need to wire the 12VDC from the alternator to a DC-DC charger and then to the Bluetti?
Or, is there a better way?
Thank you again so much. Sorry for my naivette. 
law
Check out this thread for charging direct from vehicle battery to a 12 volt to 48 volt step up converter yielding around 575 watts of charging power from a vehicle. It is long and the part you want to see is a little over half of the way through. Dual charging PV and 110V
Law, your goal (charging AC200P in trailer from tow vehicle) is reasonable, but unfortunately the design and construction of such a system does require some knowledge of electric circuits and many decisions informed by calculations. For example:
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Yes, you will need a DC-DC “charger” or “converter”, to produce the voltage required by the AC200P’s MPPT charging input (the “aviation plug” normally connected to solar panels). As Scott-Benson said, one option is a 12V-to-48V converter.
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Assuming that converter is located in the trailer, you have to worry about meeting the minimum input voltage requirement for the converter. The issue is the “voltage drop” on the long (and typically small-diameter) circuit path running from your tow vehicle battery/alternator to the 7-pin connector to that converter. To calculate that voltage drop you have to know the size of the wiring (both + and - wire runs) and the current the 12V-to-48V converter will be pulling from the tow vehicle. Calculating that tow vehicle current draw is not trivial.
You may find that new (larger) wiring is required all the way from the tow vehicle battery/alternator to the converter in the trailer.
- The final challenge is to guess whether the additional tow vehicle current calculated in #2 will or will not significantly shorten the life of your tow vehicle’s alternator. The sad fact is that the manufacturer’s “current rating” for most vehicle alternators is not defined for continuous loads (like charging your AC200)—it is a short-term peak current rating. The other sad fact is that vehicles do not monitor the load on their alternator, and warn the driver when the alternator is overloaded (i.e. when it’s too hot). You won’t know your design damages the alternator until it fails.
Having said all that, I have implemented charging of my AC200P from my vehicle. For me, it was expensive and time consuming. And I remain vaguely worried about my alternator’s health. Folks with more knowledge and bigger alternators may report a better experience. 
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Excellent reply…I think the only feasible way to use a step up voltage converter would be to have the converter close to the tow vehicle battery and the AC200 in the tow vehicle as well. Even running the 48 volt DC current from a tow vehicle to the towed vehicle would as you mention require some substantial wiring. There is no easy way to get a large volume of electrical current from a tow vehicle to a towed vehicle.
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Thank you all for your expertise. I did purchase the Max. My ultimate goal for charging it is to use solar in conjunction with shore power and/or gas generator, as necessary. I thought that charging from the alternator in the interim before I buy my panels would be simple… Oh well.
New plan is to put one large flexible panel (375W or better) on the roof for charging all the time and then some SP200s (thinking 3) to set out to catch rays when my little rig is stationery and needs AC.
So, my next questions for you very kind and helpful folks are:
What kind of large panel for the roof should I use (was dreaming of waiting for a Maxeon Air)?
Can I charge the Bluetooth AC200 Max from the 375W roof panel and 3 sp200s at the same time?
I realize that, in the above setup, I will rarely get close to the potential 975W solar potential. However, a very low power mini-split AC unit (9K BTU) should be able to run, shouldn’t it?
Thank you again for your help.
Law
Sorry, I meant Bluetti, not Bluetooth… darn computer.
Charging from a vehicle electrical supply is simple if you use car charging mode. But…the catch is you will see only around a 100 watt charge rate. Charging with your vehicle at a faster charge rate is a little more complicated.
Mixing solar panels with different capacities gets complicated as well. You will generally get the performance from the least capacity panel. (SP 200) and the 375 watt panel would be downgraded. There is a lot more to it but that is the simple answer. A chain will only be as strong as its weakest link.
Yes you can charge at the same time but you will not received the combined potential total watts as indicated above.
A 9,000 btu AC unit will most likely exceed your incoming charge wattage from panels but you will be able to run it. The question is how long and that depends on your environmental conditions.
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