AC300 Split Phase Mode

Hi Everyone.

I would like to check if anyone knows how or when you should plug in the AC Charging cord for the two AC300 when entering Split Phase Mode?

According to the manual, it says "Please disconnect the AC charging cable for both AC300 units while binding into Fusion Box Pro. "

So does this mean that the AC power cords need to be disconnected from the grid, then you make your connections with the fusion box and enter split phase mode under battery power only? Also when do you plug in your AC charging cable? Only after the split phase mode is successfully bounded together?

Thanks in advanced.

I have this same setup. I believe the caution is to prevent feeding both AC300 units from the same phase while changing the settings to Split Phase. At the same time the “AC out” must be off.

After connecting both AC300 units, the “Master” will control the “Slave”, so you power the entire setup from the “Master”. The two lower indicators on the Fusion Box Pro will light up to confirm that the “Split Phase” is working.

I used my multimeter to measure the 240 VAC at the L14-30R outlet (a picture was posted at another page). Then I connected the two AC charging cables to the two diffetent phase inputs.

So have you supplied AC input power to your two AC300’s while in split phase mode yet? If so, what were your steps… did you have to have the AC input cords disconnected before entering split phase mode?


In order to simultaneously charge both ac300 while in split phase mode, you need to acquire a special split phase ac power charge cable from Bluetti specifically for split phase charging. Be careful because The standard 15a charge cable that comes stocked with each ac300 may damage the ac300 if used to charge while in split phase mode and void your warranty. Each unit are in different phases while in split phase and if you charge using wrong phase, that would be an issue.

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I believe these special ac split phase cable may just become or will become available and probably not many if any ac300 owners have them yet. So to charge these units, go back to single phase mode to charge them and then reconfigure back when done.

I have asked Bluetti about that special cable and they replied that it will be available this month (May). I am building my own version for less. Search my other posts related to the AC300 and split phase operation. I will post new pictures after completing the cable.

Yes, the AC input must be disconnected before setting to Split Phase. And both AC plugs must be inserted in different phased outlets. The best way is to use a L14-30P with a two outlet box, where each outlet is wired to the two live wires seperately.

Here is a picture of my setup:

On the wall, I have the 240 VAC inlet receptacle on the left (the Fusion Box Pro output cable is plugged into it) and the 240 VAC outlet receptacle on the right. I am using a special L14-30P and a prewired yellow dual outlet box from my Libman 7.5 kW gas generator to feed the two AC300 stations in the large box on the far right. That only supplies 15 A each. My construction will replace that part and feed 30 A to each AC300.

Hi Raymondjram,

For my friends setup we have two separate 120v 15 amp outlets that are on two different breakers and are on different phases of the grid power.

Can you provide step by step instructions on how you enter into Split Phase mode with the AC Grid cables… we’ve tried this on our end and our fusion box shuts down after plugging in the second unit and we get several errors (011, 024 and 064 errors).

For example, can you provide us this:

  1. disconnect the ac cables
  2. connect the communication cable between the master and slave units
  3. connect the fusion box pro
  4. etc…

this will help us out allot as we’re struggling to get this working.

Also do you have PV (Solar) charging on your system?


Hi t4602yf,

The Split Phase charging cable is only needed for those who don’t know how to verify and/or deliver two phases of grid power to their two AC300’s. The objective is to take a 240v outlet and split the two hots into two different output outlets, one for each unit. I’ve already confirmed this with Bluetti support personnel.

Good. Sounds like you know what I am talking about.

The ac300 master controls and knows which ac300 uses which phase. The up or down sine wave. My concern is just plugging in a random ac power input from the 2 phases of the outlets, I figure you have a 50/50 chance of getting the right phase to correspond to the right ac300 with the ac power cable. Maybe I don’t fully understand it.

On the L14 devices, either plug or receptacle, one line is marked as “X” and the other is “Y” . So you must assign one AC300 as the “X” phase and the second one as “Y”. Then select one AC300 as “Master” ( I suggest the “X” phase) and the second as “Slave”. The communications cable will let the Master control the Slave, including powering on and off, and keep its output at the opposite phase (180 degrees of the sine wave - some math can explain this). Thus the AC input cables must plug in or wired correctly to the corresponding “X” or “Y” connection. Both neutral wires (white) go to the “W” or “N” connection, and both ground wires (green) go to the “G” connection.

The Fusion Box Pro is also intelligent, and monitors the phases, so its two indicators near the input cables will light up. As a confirmation, the output at the L14-30R outlet will have 230 to 244 VAC (depending on the AC300 efficiency) when measured at the “X” and “Y” contacts. If the two inputs were not in opposite phase the output voltage will be less, and if they were in phase, the output will be zero volts.

The design is well done, but the TT-30 plugs of the Fusion Box Pro and the receptacles on the AC300 are weak and can slip out.

with 2 ac300’s hooked via the fusion box pro & only charging from solar, if you have the solar plugged into the master, does it charge all the batteries through the master? have 2 b300’s with each system. Also when the whole system is hooked up, do you have to have 2 transfer switches hooked to your panel & then each ac300 is hooked to a different transfer switch or I guess what I am asking is when you hook these two units up with the fusion box, do they just become one with double the power? so you have solar coming into the master unit & the master unit is charging the batteries for both systems & the master unit is feeding the transfer box?

No, the two AC300 do not share any power coming in or going out. Each is on it’s own separate lines.

To provide more context on what Raymond says about the fusion. The newer fusions, will not engage unless it see’s that both AC300 are sending opposite phases to create 240volts. In addition, the newer fusions do not ground the L14-30 outlet on the fusion back to both AC300’s. It only grounds back to one AC300, they other is not connected. According to support this is by design.

No, you only have one transfer switch. Your transfer switch will receive one hot wire from each of your AC300’s. One will go to Leg 1 and the other to Leg 2.

If your not familiar with Breaker panels, I would suggest you watch video online to understand how it works.

Ok, so the 1200 watts of solar I have coming in on my “master” ac300 is just for that unit. Even though the two ac300’s are hooked together through the fusion box, I would need another 1200 watts of solar coming into the slave ac300? And even though the two units are hooked together via the fusion box, there is only one transfer switch between both ac300’s & that hookup is between the fusion box & the transfer switch. Does this sound right? I am setting my ac300 up right now with 1200 watts of solar. I am waiting for my other ac300, so am on a fact finding mission. One of my goals with the ac300’s is to power my furnace & central AC 220v circuits along with some low wattage stuff, like LED lights etc.

You are correct, the 1200 of solar you have will only charge one AC300 unit.

So if you’ve ever wired a 240 volt outlet you should know that there are two hots (one red, one black wire), a neutral and a ground wire. The fusion box takes the hot from your master AC300 and assigns it to the red wire. Then it takes the hot from your salve AC300 and assigns it to the black wire. The Red wire is -120v and the black wire is +120v and therefore gives your L14-30 outlet on your fusion 240v for a large appliance or for a transfer switch.

Do you know how a normal breaker panel works?

Hello David:
Thanks for the breakdown of the fusion box.
On a regular panel you have a hot (black) neutral (white) going to a buss bar for neutrals & a ground (green) going to the ground buss bar.

I would be plugging my fusion box into my transfer switch so I could power up my furnace (220) & my AC (220) along with some other low power circuits (lights etc. )

Thanks again for the info, appreciate!!

I have a split phase setup.

I want to charge the batteries from a single 120V Honda generator when the utility power is out, even charging them one at a time, if I have to.

My plan is to purchase two T500 AC-DC chargers and plug one into each AC300. Each inverter will only see DC power and should have no knowledge or effects from the single phase 120V AC power source powering two T500s at the same time.

Not my favorite approach, but otherwise I would have to shut down both AC300, remove the communication cable, bring them back up in single phase mode (and re-cable to the generator) with the AC power output off. Reversing the procedure after the charging was complete and having no AC power during the charging.

Prone to mistakes and confusion at best.

It seems easier to charge them both at the same time with DC chargers.

It’s a shame it’s only 500W of charging, per AC300, at a time for the T500.

I assume that the 500W rating is the output power from the T500, not tthe input power.

Even at a 90% efficiency, that’s 556 watts consumed by each T500.

My little Honda EU2200i is rated at 1800W continuous, so a pair of T500 might consume around 1112W.

If I was sure that the power supplies were 90% efficient (never consumed more than 556 watts for the T500), I could use four T400 for an estimated 1778W total. That’s a bit too close to the 1800W continuous rating of the generator and it’s still my assumption that the power supply is 90% efficient.

I can’t find any technical specifications for the T500/T400 power supplies.

Other ideas worth considering?

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I went down the rabbithole because I similarly found this warning frustrating and who the heck has a 30a l14-30r in their basement to charge with?

Support was REALLY Helpful , so sharing here to help others:

First I asked four questions based on my research. They responded to each:

  1. When in split-phase mode, it’s best to charge both machines with a split-phase charging cable.
  1. Yes. You can bypass the AC300 and charge the batteries directly by inserting a T500 into each battery.

  2. You can use the charging cable included with AC300 to charge, but you can only charge one machine at a time. The live wires for charging two AC300 cannot be the same (L1), and the two live wires need to be separated (L1 and L2).

  3. (This was last resort, but I had to ask) Yes, you can use the AC300 in phase and then reset it to single phase, disconnect the comms cable, then use the normal AC charging cable, charge it, and then return it to phase/reconnect the comms cable.