AC300 split phase recharging

I’m jumping the gun here. Mine are still on the way. But, I’m trying to get everything ready.

When 2xAC300s are connected in split phase, can I charge one battery bank at a time using 120V? We end up involuntary going off grid for 7-10 days every year. My setup should last 4-5 days before needing to recharge. I have a small generator that I want to use during extended outages. It only has 120V out. I estimate that I can run it ~8-9 hours/day(one tank of gas) to keep the batteries mostly charged. I was hoping to charge battery bank A one day and battery bank B next day. Never charging both AC300s at same time.

I know the best solution is to get a 240v generator. I figured the batteries were the most important part for power outages, my wife can easily switch to battery power. But, after buying the batteries I’m going to have to wait a while before any more upgrades to my backup power.

First of all, how many batteries did you buy? Remember, Never charge both units on the same 120 volt generator! The load is the secret, when the power goes out, I cut my load down to the critical units only. My systems could not run 4-5 days with 5 kw solar panels to charge them up during the day. Have fun, my wife thinks this is my hobby and never will pay for the cost of the system.

I purchased 8xB300 batteries. I understand not using same generator on both, at the same time. I wasn’t sure about not having the charge balanced between the two units. I also have the the Smart Home Panel coming. I think the wife will just needs to turn on batteries and flip a switch. We will only have a few “emergency” circuits on the sub panel. My wife thinks the same, about payback. I bet both of them will be happy when the power goes out. My electricity is so cheap, I’m not planning solar panels yet. So, my only payback will be saving the groceries in fridge and freezer.


I live in a cheap electric area too, only 11 cents a kwh. I think our wifes should get together and share their views about our solar systems. Your total batteries are great but solar panels will help. I have 1500 watts (6 panels of 250 watt) on each unit. I have two ep500s and one ac200max with two b230 batteries. My EP500 runs so much better than AC200Max because it has only one battery management system instead of three on the AC200Max. Have fun putting up your system.

Sorry to jump in and little off topic - but you mentioned you like the EP500 better than the MAX, and I am looking at both for steady home use. Two questions:

  1. Any issues with the EP500? Is it a Pro?
  2. How did the EP500 ship? I am a little concerned about getting and handling something that heavy in one piece.

#2 - in a box, I had the same worries, but after two units came, I became an expert in unpacking them. The packing breaks away after you cut all the metal cords around it and then the bottom is a pallet that you can roll off after you break off the white style foam around the wheels. it is very easy to roll around on my floors.

#1 I have the EP500, two of them and they are connected to the split phase fusion unit. The biggest worry is not to exceed 2000 watts, so balancing the load has been fun. I run kitchen appliances on one unit and heater( during the winter) and air conditioner( during the summer) on the other. Never had a problem with overcurrent/voltage, YET.
I bought the AC200 Max because of the lighter weight, but when I run the unit and two B230 batteries, the overhead of the BMS kills the batteries so fast that now I turn off the B230 batteries and use the AC200Max alone. On cloudy days I will add the B230 back in with AC200 Max and charge them with the wall 500 watt power supply. (PS the 500 watt power is plugged into the EP500 that is using the UPS feature.

I hope I did not confuse you, but I would buy another EP500 instead of AC200/AC300 unit.

As described in the AC300 user manual, you cannot charge the B300 batteries through the two AC300 in split phase with two 120 VAC circuits on the same phase. You can do two options:

  1. Buy (or fabricate - I had to buy the parts and fabricate it for my own setup) the special AC Charging Cable for Split Phase that has a L14-30P on one end, and two SP29-30 three pin female aviation connectors on the other. Bluetti sells it for $100. This will allow you to charge both AC300 units at the same time using the two separate phases of your utility 240 VAC circuit. I recommend adding a 40 A circuit breaker to your outlet to protect the AC300 setup. Here is my fabrication.

And here is Bluetti’s offer (they look similar, even with the same connector colors, but I did mine last year, so I did it before Bluetti did!):

With this option, you can still take out 240 VAC power through the Fusion Box Pro for your home while charging at the same time up to 30 A on both AC300 units. But if the utility power fails, the Split Phase operation will drop out and recover five seconds later. This is programmed into the AC300 and not usable as a true UPS.

  1. Take both AC300 units off the Split Phase, and back into Single Phase. You can charge each AC300 independently even on the same 120 VAC circuit, but only using the original 120 VAC cable and dropping the AC input current to 15 A. I had to do this when Hurricane Fiona hit my home, left me without power for eight days, and I used my gas powered generator to charge my batteries. It takes much more time but it is cheaper. After the B300 batteries are charged, remove the 120 VAC cables, then set the AC300 units back into Split Phase and start the AC output on the Master AC300.

I hope this information will be useful for many here who have two AC300 and several B300 units in a Split Phase 230 VAC setup.


Note: This observation and question is for the AC500, not the AC300 specifically.

After spending a ton of money on the split phase option, I recently read a similar post on the forum before getting the remainder of my equipment to do a test. I did the test, and as expected, I can’t charge from a single phase while in split phase mode.

In single phase, I have not had an issue charging both battery banks from a single phase after setting the amperage to a reasonable setting (12amp/12amp on a 30amp pedestal to meet the 80% continues regulation). This is done with the split phase charging cable and haven’t needed to switch out to the main cable as long as the two inverters are in single phase mode.

This is a little disappointing as the point of the two phase system was to still run 240v/50amp in my RV while being able to charge on a 30amp 120v pedestal when a 50 amp site isn’t available.

After thinking through this, I understand that the system is expecting two phases to pass through to the main panel while on grid vs. having the batteries completely isolate the power source, provide the dual phase output but charge the batteries as needed in a single phase.

We rarely use so much electricity that our batteries couldn’t buffer us during excess usage, deplete a bit, but fully charge while on a single 30amp/120v circuit. But, there are times we have to be mindful of not exceeding 30amp/120v (50amp/120v with my own cable I created to do what I described in single phase).

With that said, I want to confirm the following with the #2 option above. When taking the inverters out of split phase mode to charge the batteries, I believe you also have to kill the AC output as to not provide two independent phases to the RV during the charging period. Is that correct?

If my hunch is correct, I’d say it would be really nice for Bluetti to add an option to turn off passthrough from the grid, allow dual phase on the output side while isolating the input so that it could be charged on a single phase.

Not sure this could be done with firmware, or if the way the hardware is currently designed it’s not possible.

My answer is still related to the AC300 but may be similar for the AC500. I did a test to charge one of the two AC300 units with a single phase 120 VAC cable while active in Split Phase and it will not charge at all. The only way you can charge with 120 VAC is in Single Phase. I disabled the Split Phase by setting one unit back to Single Phase and it charged. And if you set both as Single Phase you can charge both with the Split Phase cable because you are using two 120 VAC circuits.

I suggest you to test your AC500 setup and confirm the same situation as I did.

Hi @Raymond,

Thank you for the response. I did test the charging side of the equation. My question is related to the AC output side of the equation. When you set the units to single phase, did you have to shut off the AC output from the AC300 going to the house, or were you still able to power at least a single leg of the house while taking the units out of split phase to charge? I suspect you had to kill power to the entire house to charge the batteries but curious what your experience was.

Thank you,

from what i understand you would run second transfer switch that would feed your main panel the output of your gas gen. to your ac300’s ot would look like grid power and they both will charge as normal.