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Question FlexBoss Intermittent Communication Failure with Battery and Discharge

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Posts: 4
Topic starter
(@liquidrobot)
Active Member
Joined: 3 weeks ago

I have a FlexBoss + GridBoss + 3 x EG4 Wallmount Indoor 280AH Lithium Batteries. No solar yet so this is just providing whole house backup. In general it has worked well and I have tested the battery backup a number of times during install and it has worked through actual grid outages as well. But about once per month, I get the following sequence of events in my log:

  • Communication Failure with Battery
  • Battery Voltage Low (about 5 hours later)
  • Battery Open (about 30 min later)

After the first event, the SOC drops instantly to 50%. Then about a week later the SOC drops instantly to 0%. My charts never show any battery power being used. When I am next onsite (this is installed in a vacation house), I can get the system working again by turning all the batteries off and then turning them back on again. At this point, the batteries charge up from 0% to 100% like normal over the course of a couple hours, pulling 12KW during that time as expected.

I updated all my firmware at the end of April but then it happened again even with the current firmware. I have done some searches and have not seen this type of failure reported. Any ideas about what is happening or how to prevent this?

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6 Replies
Posts: 1
(@rjacoby48612)
New Member
Joined: 6 months ago

I have the same exact system and I am experiencing the same problem! Happened this morning at 8:00, the last time it happened was 6/04/25? Have you had any response from EG4?

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EG4 Eric
Posts: 465
(@eg4eric)
Reputable Member
Joined: 9 months ago

Do you happen to know the battery voltage when these warnings appear?

It’s possible that some of the battery cells are out of balance.

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Posts: 4
Topic starter
(@liquidrobot)
Active Member
Joined: 3 weeks ago

Looking at the logged battery voltage is interesting. It generally is around 52-53V. Around a week before the event, the voltage starts dropping very slowly (about 0.2V / day). Then a couple days before the event the voltage starts dropping more quickly up to the event. During this entire time the house is being powered fully by the grid and the charts show 0W going in and out of the battery. So I’m not sure why the voltage is dropping. Here are plots of the voltage over the three days leading up to the event:

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Posts: 4
Topic starter
(@liquidrobot)
Active Member
Joined: 3 weeks ago

And here are plots of SOC, vBus1, and vBus2, all showing a change at the same time that I get the message for “Communication Failure with Battery”

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The later change on Vbat_Inv corresponds to the message for “Battery Open”:

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