FlexBoss21 - Battery Low Voltage error - Main Thread

RE: FlexBoss21 - Battery Low Voltage error

Umar — Tue, 07 Oct 2025 17:28:02 +0000

@eg4eric Hi,

If we were to make longer wires what type of wire can we use aluminum/copper awg?

Also we have some extra wire which came with the batteries not sure if it would be possible to use a coupling to extend them or if that would even be safe to do.

Thank you

RE: FlexBoss21 - Battery Low Voltage error

EG4 Eric — Tue, 07 Oct 2025 14:58:05 +0000

You can make your own wires; however, if that’s not something you’re able to do right now, we can continue troubleshooting and revisit this step later if necessary. In the meantime, you can top-balance the batteries by using a 48V battery charger or setting the inverter to Lead Acid mode to charge the battery by voltage to 57V. This will help recalibrate the SOC. I’ve attached a document that explains how this process works.

EG4-Indoor-All-Weather-280Ah-Battery-Recalibration-Guide.pdf

RE: FlexBoss21 - Battery Low Voltage error

Umar — Mon, 06 Oct 2025 15:04:52 +0000

@eg4eric Hi,

So I ran into an issue with trying to rewire the batteries. Due to the way it was installed originally, the inverter is installed over the battery at the end. Unfortunately the wires aren't long enough to go from the inverter to the center battery. Is there a recommended way to extend these wires? Is there anything you can provide which would help in this situation? As mentioned before I checked wit the EG4 team before having it installed in this configuration.

Thank you

RE: FlexBoss21 - Battery Low Voltage error

Umar — Wed, 01 Oct 2025 11:47:09 +0000

Ok I will give re-wiring a shot provided the wires are long enough as the inverter is installed over the battery at the end. Coincidentally I did check with EG4 team before wiring it the way I did and they confirmed it could be wired that way.

As for the voltage I am not sure, but yes when I say fail they are depleted and at 0% and need to be fully recharged.

Something else to consider is I have a CT sensor on the line between the gridboss and flexboss and it doesn't show the drain. Neither does the EG4 monitor site so I am of the opinion the drain is happening internally either in the batteries themselves or between the battery and the flexboss.

Re-wiring and waiting to see if they fail might take some time but I will come back and let you know what happens

RE: FlexBoss21 - Battery Low Voltage error

EG4 Eric — Tue, 30 Sep 2025 22:02:09 +0000

If possible, I recommend wiring the batteries as shown in the image below. I'm not saying that this will resolve the issue completely, but it could be the majority of the problem.

1809

Do you know the voltage of the batteries when they are at 60% and then when they fail?

Just want to clarify, when you say fail, do you mean they are depleted, and they are at 0%?

RE: FlexBoss21 - Battery Low Voltage error

Umar — Tue, 30 Sep 2025 17:17:59 +0000

Just wanted to add that another family member has the exact same setup and is also facing this issue

RE: FlexBoss21 - Battery Low Voltage error

Umar — Tue, 30 Sep 2025 17:11:54 +0000

@eg4eric they are connected in series. The first battery is connected to the FlexBoss and the other 2 are chained after it. On a side note I also have the GridBoss and my solar is AC coupled to it. No solar is going directly to the FlexBoss
1808

RE: FlexBoss21 - Battery Low Voltage error

EG4 Eric — Tue, 30 Sep 2025 16:12:37 +0000

I apologize that no one has been able to get in touch with you. We have been receiving a high volume of emails, but we are responding to them in the order they are received

However, I can offer some assistance to you.

You have 3- EG4 WallMount batteries? how do you have them connected?

FlexBoss21 - Battery Low Voltage error

Umar — Fri, 26 Sep 2025 16:08:12 +0000

Hi I have the flexboss 21 running with 3 indoor batteries. I bought this for home backup during outages.

I originally had it in backup mode but every 5 weeks or so the batteries would fail and with "low battery voltage" issue.

I have since changed to Self consumption mode so the batteries charge in the day and are used at night. Originally I set Off-Grid Cut-Off SOC(%) to 60 but then same issue if it fell below 60% the batteries would fail. I then lowered that value to 10% cut off but alas the SOC fell to 6% two nights ago and the batteries failed again.

Seems there is a bleed issue and it's not being tracked. Each time the batteries fail I have to physically reboot the batteries for them to start back charging.

I tried to email support but got no response.

Any suggestions help would be appreciated.

Also anyway to get notifications email or text when there is an issue? I don't know these issues happen unless I login to check the system.