Hi all, We have two AC500 with one each B300S running in dual phase. The PV priority setting has worked like a charm for the past year. We expanded our system with one B300K per system and now it won’t switch to the grid. Last night, it bypassed the set SOC setting, and the system shut down. This morning, I isolated each battery, and all four said that the firmware is up to date.
I’ve tried everything that I’ve read to no avail. I believe it’s a firmware issue as all four batteries are recognized and charging. Please help as our system won’take it through the night nor through my work day on Monday. 
Hi @bviwahine, We truly care about the issue you’ve raised. Could you please share a screenshot of your UPS settings page, along with the SN code and firmware version of your AC500?
We’ll check to see if the issue can be resolved.
It won’t charge or recognize the grid in any configuration. I’ve tried single phase, dual phase, no solar connected, solar connected, nothing. The grid is not recognized.
I’ll have to send the ac500s firmware versions when I get home tonight as it appears the wifi needs updating.
Hi @bviwahine, We have applied to upgrade your BMS, our IT department will push the latest version of firmware to your machine in 24 hours. Please upgrade it tomorrow.
Please only connect 1 B300 with the AC500 each time, and do not load any device when upgrading it.
After that, please do a complete cycle of discharge and charge to correct the SOC. The problem will be resolved.
We also suggest you first set it to standard UPS mode and then try charging.
Additionally, you can also try disconnecting the connection and using solar panels to charge each B300 individually, which is also an emergency charging solution.
Please let us know if it does help.
Thank you! More than likely I will do the upgrade on Thursday when I more time. Please confirm that I should have only the one new B300K or the previous B300S hooked up while doing the upgrade (or does it matter)?
Hi @bviwahine, We have now pushed BMS v1022.14 and BMS v1067.13 to your two AC500 units.
Yes, each time please only connect one battery that needs BMS firmware upgrade during the upgrade process.
Hi,
I had no trouble with the upgrades. I did each battery individually and they were successful.
How should I do a complete cycle of discharge? I set the system to standard UPS, charged the batteries by solar, and let them deplete (the master depleted much quicker). The system still won’t charge from the grid. Please advise as to how to proceed or what I did wrong.
The system charges evenly from the grid, recognizes all four batteries but simply won’t charge from the grid.
Scottie
My suggestions:
- Disconnect PV completely
- Disconnect Grid completely
- Set AC500 to Standard UPS mode
- Discharge the complete System with a good load, e.g. an AC unit or a heater or sth else
- Discharge until all units shut off completely
- Connect grid to the units and let them charge until they are completely full
- Do not connect any load to the units until fully charged
- Set back your preferred UPS mode to the AC500 units
After that the units and the B300K’s should have 100%.
Now connect back PV and check all the settings.
Connect back your load and see if it worked.
If not you should repeat the cycle one more time to see if it makes a difference.
If that did not help you may have a support case.
Please note: sometimes you have to change all UPS settings more than once for the unit to accept them fully. I do not know why that is the case but I have experienced that several times.
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Hi @bviwahine, To help us better understand your parallel charging situation, could you clarify:
Were you previously able to charge via grid when the units were parallel-connected, or has this been attempted only with PV until recently?
Which AC500 is configured as the master unit versus the slave unit in your current setup?
For successful AC charging in parallel mode, you’ll need the dedicated AC charging cable for splite phase (standard AC cables won’t function in this configuration). This specialized cable ensures proper synchronization between units.
We’d also like to acknowledge @ftrueck’s helpful experience-sharing—such community contributions are invaluable for troubleshooting.
Hi,
Thank you, everyone, for your input.
Sorry, I disappeared for a bit. Yes, until the two new batteries I charged from solar and the grid. PV priority worked perfectly. So, while I wasn’t on the forum, we learned that the cable to the “slaved” AC500 appeared to have scorching at the connection. No idea why or when it happened. I turned one AC500 off at a time, and both the “main” and “slave” recognized the grid with the cable that wasn’t scorched. Ordered a new cable. No luck. When in dual phase, and the cable is plugged into the grid, it trips a 50-amp dual-phase breaker.
That’s where we stand, back at square one. Two new batteries and a tripped breaker if we try to charge from the grid. Yes, we do have the appropriate cable.
Any ideas? Super frustrated. 
Hi @bviwahine, Thank you for the update, and we’re sorry to hear this news.
Could you please take a video showing us how you installed and connected them, how the circuit breaker trips, and the condition of the cables? Please upload it to a cloud drive and share the link with us. This will help us further investigate the issue.
Hi,
Thank you for your reply. The home installation kit was bought from Bluetti and was installed per specs by an electrician. We just replaced the cable, so it’s new. I won’t have time to make a video for another day or two.
Yesterday we had the electrician come check everything. There are no shorts anywhere. The AC input on the AC500 is fine, as well as the plug and the cable. The cables are receiving power but the Bluetti doesn’t recognize it. I was thinking of factory resetting everything and seeing if it helps. However, I don’t remember the code for the advanced settings.
Your thoughts on a reset?
Scottie
Uploading: VID20250727122442.mp4…
I did a factory reset, but it was no help. Here is a video of the home integration kit and our AC500 system. It all worked flawlessly until we added the two additional batteries. Now, if the AC in and out are plugged in, it trips the breaker between the transfer switch and the AC500s. No grid power/charging ever.
[Blettie system]
Hi @bviwahine, Thank you for submitting the relevant information.
We would like to view your video, but we need to apply for permission. I have already sent the application using the email with the suffix “poweroak”. Please approve it as soon as possible and notify me, after which we will analyze this case.
HELP 
Ok, I’m back. I did give permission for the video.
So, it took a while as we went on vacation but the electrician finally came to check things out. The setup is a main breaker that allows the house to run off the grid or the AC500s. There is a 50-amp breaker between the grid and the AC500s. Everything checks out. The electrician believes it’s possibly a circuit board issue within the AC500 regarding the split-phase charging input.
Just a reminder, we have (2) AC500, with the B300S in split phase and running in PV priority. It worked perfectly for over a year. We added the expansion batteries, B300k, and ever since, the system will not accept grid power for charging with the 240 split cable. They will charge with the 110 cables.
The AC500’s, grid input amp is set at 40. If the split-phase grid charging cables are plugged into the AC500, but the 240 output cables (to run the house) are not plugged in, the 50-amp breaker won’t trip. There’s still no charging but the breaker won’t trip. If the split-phase cables to the house are plugged in the 50-amp breaker, it trips.
I’m giving this information in the hope that it gives some more insight. We are getting desperate. Otherwise, I guess we are looking at a blown circuit board. Why? Working perfectly, added expansion batteries, no 240 charging.
Hi @bviwahine, Thank you for providing the detailed information, and we have also successfully viewed the video you shared.
It seems the issue is related to the B300K. Please test the following: disconnect the B300K, then connect each AC500 to one B300S respectively, and charge them via the 240V power grid. Could they work normally?
If they work properly, please further test by using one AC500 to connect to a B300S first, then connect the B300K, and charge via the 110V power grid. This will help us troubleshoot which specific combination is causing the issue.
I disconnected the B300K’s and connected the 240 charging cable, but it did not recognize it, so no charging. It will charge in single phase with the 110 cable.
We disconnected the B300S and connected the B300K still, there is no 240 charging. It will charge with the 110 cable while in single phase.
The grid comes into the house through a 100-amp breaker. The breaker going to the AC500s is a 50-amp breaker. Is this correct or should it be a higher/bigger amp breaker with the two batteries per AC500?
The 50-amp breaker doesn’t trip as long as the 240 out (to run the house) is not plugged in. If it’s plugged in the breaker will trip.
The second time, the 50-amp tripped, and the 100-amp also tripped. Ouch.
Thoughts