Using AC300 24/7

My understanding is this is precisely what the AC300 and AC500 are designed for. I’m using a very similar setup to you. I have an AC300 + 3 x B300 batteries + Reliance ProTran 6-circuit transfer switch. I’m using both PV inputs, which will supply the max 1200W each during peak daylight hours. The PV array is 12 x Renogy 320W panels. I’ve been using that setup 24/7 for about 6 months now, and it’s been running fine. I’m powering 80% of my home, which consists of all primary living area lights and power circuits, minus the kitchen oven/microwave (50A circuit), HVAC and outdoor electric. One of the circuits supplied by the AC300 is a GFCI, and it’s running fine. All other appliances, including refrigerator and freezers are running on the AC300. I’m located in CA, similar to FL, and my AC300 is located in the garage. The fan will come on periodically, usually when being charged at full 2.4Kw capacity, and the unit never gets more than just slightly warm. My unit is running in PV Priority UPS mode, with the SOC limit set to 20%. With 3 batteries and 4 or more full sun hours per day, this configuration will provide enough power to make a full 24 hour cycle without having to pull power from the grid. I had to add the third battery (9.2Kw total storage) to enable the system to make a full 24 hours. Based upon my research on LiFePO4 batteries, I’m hoping to get approximately 10 years of daily charge/discharge cycles out of them before noticing any apparent degredation problems.

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Heh, that’s asking for trouble. They might decide to raise your rates on a whim. As it is, they charge you more for little things, like owning a dog; cats seem to be okay, even though they are notorious for chewing exposed electric wires. Car insurance companies charge more for red cars and/or if there is a floor shift. It means you’re an aggressive driver.

In your case, because you have the Pro/Tran transfer switch, you are correct that as long as you do not use the outbound AC and inbound AC (charging) at the same time you’ll be fine. If you have a date of Dec 2022, then you have a 2nd Gen AC300.

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Thanks for the confirmation! :+1:

I have read many of your helpful Bluetti posts-thank you and I hope you can help me.

I bought an AC300/B300 11/2021 as a UPS and this year purchased an additional AC300/ 3 more B300 as part of a soon to be installed hybrid (grid and solar) system employing 30 x 365W Qcell panels/Solaredge inverter/Bluetti home installation kit to supply a home using an average of 60 KW/day and to enable split phase mode/240W outlet to Level 2 charge a 12 KW hybrid vehicle.
My questions are:

  1. Can I use split phase mode safely if I use the newer AC300 as the Master unit(including charging from AC power coming thru the main panel delivered thru the 30A Split-phase AC Charging Y shaped cable and output using the 2*TT-30P to L14-30C to a Reliance Controls Pro/Tran 2 310A set to “GEN”)?
  2. Do I need a surge protector anywhere?

I hope to hook up 8 roof panels(VOC 80/mppt) directly to the AC300’s.

Assuming that you will be connecting both AC300 units (not just the master unit) to the grid input, I think both AC300 units would need to be the floating neutral type (not the older type which “passes” input neutral bonding to the output). You can test each AC300 unit to determine the type. First measure the voltage between the hot and ground connectors of your grid power outlet. There should be 120V between hot and ground (if your main service panel has the expected neutral bonding). Then with each AC300, connect the grid input and enable AC output. Then measure the voltage (using any of the AC300’s AC output outlets) between hot and ground connectors. If there is 120V between hot and ground, then the AC300 is of the older type and needs to be replaced by Bluetti. If there’s no voltage between hot and ground, then the AC300 is of the newer type and should be safe to use with Pro/Tran 2 310A.

I’m in the process of a similar configuration (split phase with Pro/Tran 2 310A). I tested my AC300 units and found one of the them is of the older type. Bluetti is replacing the unit, and I’m waiting for the replacement to arrive before connecting to the Pro/Tran 2 310A.

I plan on connecting the 2 AC300’S to the grid with a 30A split phase AC charging cable and to each other with the communication cable(both provided in the kit).
I don’t own a multimeter or neon circuit tester, but I was able to determine with a receptacle tester that the older AC300 has an “open ground” pattern which is not present on the newer AC300(both Ac300’s were attached to the grid and had AC output on). Is the difference in the ground pattern between my old and new AC300 sufficient to warrant replacement of the old unit or do I need to test with a multimeter or neon circuit tester?.

Thank you

A basic multimeter is an essential tool to have. For the split-phase connection that you want to create, I’d recommend measuring various voltages at each step of the setup.

I’m a little surprised that it’s the older AC300 that has the “open ground” behavior. I think “open ground” is same as “floating neutral”, which actually is the desired behavior for use with transfer switch (such as the Pro/Tran 2 310A) that does not switch the neutral. If I were you, I’d feel more comfortable with multimeter measurement to make sure.

By any chance do you have a neutral bonding plug (such as Another way to test is to connect each AC300 to GFCI grid power outlet, enable AC300’s AC output, and then plug a neutral bonding plug into one of the AC300’s AC outlets. If the GFCI grid power outlet trips, then the AC300 needs to be replaced before using with Pro/Tran 2 310A.

I don’t know whether Bluetti technical support will accept the receptacle tester result. For my replacement, I created video showing both the multimeter measurement and the GFCI grid power trip with neutral bonding plug. From that, Bluetti technical support determined that the unit needs to be replaced.

I rechecked and now both units consistently read “correct wiring” while connected to the grid/home outlet, and only the NEWER unit reads “open ground” when NOT connected to the grid/home outlet.
I became concerned that “open ground” is analogous to open (not floating) neutral in that open signifies unconnected- and therefore ungrounded and unsafe, So I plugged the newer AC300 into a GFCI outlet. I hypothesized “open ground” should trip a GFCI outlet. WRONG, it didn’t.

I obviously have a way to go before I would feel safe with my hoped for split phase hybrid home backup.
For now, I will connect the newer AC300/3 x B300 in PV priority UPS mode to the Reliance Protran2 310A Transfer box switched to “Gen”. To accomplish this I will need to return the AC300 240V Home Integration kit and buy the 120V kit. The older AC300/B300 will be used separately in standard UPS supplying critical loads in my home thru the grid.

I plan to purchase a multimeter and a neutral plug.

Thanks for helping me get up to speed.

You’re welcome. A few things come to mind.

  1. Regarding the older AC300’s being unsafe for use with Pro/Tran 2 (when connected to both grid input power and the output connected to Pro/Tran 2), my impression is that the problem is not specific to split-phase mode. Even if you are connecting only one AC300 to both grid input power and Pro/Tran 2, you still need to ensure that AC300 is of the type that is safe to do so.

  2. If your GFCI outlet is near your Pro/Tran 2, you could use the GFCI outlet as a test. First test the GFCI outlet to make sure the GFCI really is working (your receptacle tester hopefully has a button for testing GFCI). Then connect your AC300 to the GFCI outlet (as grid input) and the Pro/Tran 2. Configure the AC300 input current limit to be within what the GFCI outlet could provide (so that the AC300 doesn’t falsely trip GFCI because the AC300 is drawing too much current). Then run through the various combinations (AC300 not charging from grid input, AC300 charging from grid input, no AC output load, low AC output load, high AC output load). If GFCI trips, the configuration is unsafe.

  3. If your eventual goal is to use split-phase configuration with Pro/Tran 2, I don’t think you need to return the 240V Home Integration Kit. You can still use the 240V kit’s split-phase AC charging cable (you’ll just connect one output to AC300 and leave the other output unused). You just need a TT30 to L14-30 cable (so that one AC300 could drive all 10 circuits in Pro/Tran 2 (as opposed to only half the circuits) such as

  4. When using the receptacle tester, ensure that nothing else is connected to any of the AC300’s AC output sockets. The AC300’s AC output sockets are internally connected to each other. If you have the receptacle tester in one AC output socket and an AC load connected to another AC output socket, the other’s AC output socket’s AC load could confuse/affect the receptacle tester.

  5. If both AC300 units, while connected to grid/home outlet, show “correct wiring” on the receptacle tester (and no other AC output load is connected), this would seem to indicate that neither AC300 is safe for use with Pro/Tran 2 (and have the AC300’s input be connected to grid/home outlet at the same time). Hopefully this is not the case!

  6. If an AC300 is not connected to grid/home outlet and no other AC output load (other than the receptacle tester) is connected, the receptacle tester should show “open ground” (regardless of whether the AC300 is the older type or the newer type). It is surprising that one of the AC300 units show “correct wiring” in this situation, making me wonder whether the receptacle tester result is correct.

  7. Connecting an “open ground” load to a GFCI outlet will not trip GFCI. GFCI trips when it senses that the hot connector’s current does not match the neutral connector’s current (for example, the mismatch occurred because part of the current flowed on the ground connector).

Also, if your receptacle tester has a GFCI test button, you can use that for testing in lieu of a neutral bonding plug. First verify the GFCI outlet’s GFCI protection is working via the receptacle tester’s test button. Then plug AC300 to the GFCI outlet and plug the receptacle tester into one of the AC300’s output outlets. Run the AC300 through various scenarios (no AC load, low AC load, high AC load while AC300 is/isn’t charging from grid input). Press the receptacle tester’s test button during each scenario. If the GFCI outlet doesn’t trip, that’s a good sign.

Here are the results of testing with the Multimeter/Neutral plug initially suggested. The Receptacle Tester did not seem to provide reproducible results on the older AC300.

bluetti electrical.pptx

How did you measure the voltage? It looks like you measured the voltage between hot and neutral (all measurements showed approximately 120 volts). To determine whether the the neutral is floating or bonded to ground, measure the voltage between hot and ground. If the output has floating neutral (open ground), there should be zero volts between hot and ground. If the output has bonded neutral, there should be 120 volts between hot and ground.

Based on the GFCI trip result, it seems that the newer (2023) AC300 is the one that is problematic. Does the newer AC300 have higher serial number?

You are correct, I tested with probes inserted into the hot and neutral.
0-4 volts on both ac300’s (hot to ground).
The newer unit has a higher serial #.

Unluckily it is the older unit that has unresponsive screen issues necessitating APP use to do things like turn ac/dc on/off.

Do I need to retest the older non-tripping unit while plugged into GFCI with various loads (I as I did previously on a regular home outlet)?

You are doing great, what would you do next?

I’m surprised that you are measuring only 0-4 volts hot-to-ground on both AC300 units (with grid input power connected). Your receptacle tester result (showing that the newer AC300 did not exhibit “open ground”) and the GFCI test result both point to the newer AC300 as problematic. When you measured the hot-to-ground voltage, was the grid input power connected (and neutral bonding plug should not be inserted)? You might want to retake the measurement to double check.

If your older unit’s screen is defective, I’d contact Bluetti support to get that issue resolved while the unit still is under warranty.

For the newer unit that trips GFCI when neutral bonding plug is inserted, I would also contact Bluetti support. I would describe the intended use case (wanting to use with Pro/Tran 2 310A with grid input power connected) and describe the behavior observed. I would also make a video that shows the difference in behavior between the two units. For each unit, I’d first show the unit’s serial number and firmware versions and show what happens when neutral bonding plug is inserted (whether the grid input’s GFCI trips). If you are able to show difference in hot-to-ground voltage, I would show that too.

Whichever unit(s) that you want to connect to the Pro/Tran 2 and grid input power, I would first test the unit with various representative loads and UPS modes and the unit connected to a GFCI outlet. I would also measure the hot-to-ground voltage at each load/mode to make sure there isn’t 120 volts between hot and ground.

Retested and made sure the units were connected to a wall outlet WITHOUT a neutral plug. Up to 8v recorded hot to ground on both units.

I posted to Bluetti_Care Blueeti_care ac300x2.pptx (SN#, firmware pictures, intended use and video of screen dysfunction) when I first posted in this forum. Awaiting their response.
About to send neutral plug/GFCI, Micrometer test results and video(including hot to ground and GFCI tripping).
At this point it appears that I need replacement of 1 and possibly 2 AC300 units. I wont continue my solar project until at least 1 unit is functioning safely. If the older non-tripping unit does not need to be returned, I will perform the additional testing you recommended prior to connecting it to the transfer box.
I appreciate your well thought out responses. If you have influence with Bluetti I would appreciate that as well. Of course I will post follow up.

Thanks again

I have not used Bluetti_Care; I’ve been sending my support requests via email to They’ve been pretty responsive with multiple requests. They tend to respond during US nighttime. If you send email now, you should get a response tomorrow morning. Most likely they’ll first forward to their technical staff, and you’ll hear back from the technical staff a day or two later. has already acknowledged my email.
I retested hot/ground again, probing more aggresively with/without grid connection and updated my table bluetti electrical.pptx. As you can see I did record higher voltages overall and perhaps of significance is the difference with grid attachment.

Your updated 2023-AC300 grid-attached hot-to-ground voltage measurement is what I would expect based on the receptacle tester and GFCI test results. But you should not be observing hot-to-ground voltage of 70 volts in the other scenarios. So far I’ve tested three AC300 units, and the only time I observed hot-to-ground voltage like this (approximately half way between zero volts and 120 volts) is if I measure hot-to-ground voltage with a receptacle tester inserted (because the receptacle tester’s internal circuitry interfered with the measurement).

Your result shows that one cannot rely on only the serial number or purchase timeframe to know whether an AC300 is of the type that is safe to use with non-neutral-switching transfer switch (with grid input power connected). A newer unit with higher serial number, even one purchased in 2023, might still be of the unsafe type.

I understand that the new unit is unsafe when attached to the provided subpanel/transfer switch while receiving grid power and providing AC output.
However I am concerned about the safety of the of the older unit at anytime having read that low hot-to-ground readings (specially ~ 60 v) can be seen/may be typical of a grounding issue.
Should hot to ground readings change between the grid/no grid scenario?