EG4 Battery Firmware Update Failing: The Power-On Order That Worked for Us
Our RS485 firmware update failed until we pressed Update first and powered the BMS second. What EG4's manual says.
Last reviewed 2026-10-11.
What the manufacturer documents
- The manual says to update one battery at a time and to keep the update files for one battery model only on the adapter: more than one model's files make the update fail. The same battery's RS485 (.BIN) and RS232 or Batt-Com (.HEX) files can both be on it. (eg4electronics.com)
- Compatible batteries listed: WallMount 100Ah, 280Ah and 314Ah Indoor; WallMount 280Ah and 314Ah All Weather; LL-S; LL-V2; LifePower4 V2. Not compatible: LL-V1, LifePower4 V1 and GYLL. (eg4electronics.com)
- The manual has separate Auto-ID and non-Auto-ID procedures, and the port and cable depend on the battery model (its Table 7.1). We do not reproduce those steps. (eg4electronics.com)
- The manual's RS485 sections include a note that the battery BMS must be reset once the Update button is pressed, and that the update will fail if it is not. (eg4electronics.com)
- The manual gives about 35 seconds for an RS485 update and about 40 seconds for a Batt-Com update. Success is a beep and the Success light flashing twice, then staying solid green; failure is a long beep and a solid red Fault light. (eg4electronics.com)
- The manual's changelog lists an added step for the RS485 update in version 1.0.2 and a split into Auto-ID and non-Auto-ID sections in version 1.0.4. (eg4electronics.com)
What happened to us
- In our adapter review the battery's version screen read Z02T01. The RS485 (.BIN) update ended in a Fault three times before we switched method: on a first try, after unplugging and retrying, and after deleting and re-uploading the file and using a USB power bank without Power Delivery. (video)
- We then loaded the Batt-Com (.HEX) file and moved the cable to the Batt-Com port. The adapter showed Success, but the version screen still read Z02T01, so we could not tell whether anything had changed. A last RS485 try at the end of the video ended in a Fault again. (video)
- A viewer suggested starting the update on the adapter first and then powering on the BMS. With only the RS485 cable connected, we pressed Update on the adapter, then switched the BMS on. After a wait the update succeeded and the version screen showed Z02T04; the LCD version still read 1.0.0. (video)
- We repeated the same order for the Batt-Com file on the Batt-Com port and it also succeeded. Both files were on the adapter at the same time. (video)
- Before this we had seen that on our batteries a battery sometimes stopped seeing its neighbours until we turned its BMS off and on, which is why a BMS restart seemed worth trying. (video)
Symptoms compared
| Symptom | What EG4's manual says | What we saw |
|---|---|---|
| Red Fault light and a long beep | The manual has a troubleshooting section for a failed update and says only one battery model's files may be on the adapter | RS485 failed repeatedly in our first video |
| RS485 update fails | The manual's RS485 note says the BMS must be reset after Update is pressed, otherwise the update fails | Pressing Update first and then powering the BMS worked for us |
| Success shown but version unchanged | Not covered | Batt-Com showed Success while the version screen still read Z02T01 |
| Battery not on the compatibility list | The manual lists LL-V1, LifePower4 V1 and GYLL as not compatible | Not tested |
What we did not verify
- We do not know which version of the manual we read in 2025, so we cannot say the manual was wrong at that time; the current version describes the BMS reset step.
- We did not check whether the version screen shows every firmware component, so a Success with an unchanged version may not mean the update failed.
- We tried this on our own batteries only and cannot say what happens on other models.
- We did not record the firmware version the battery was on before the update in the fix video.
- The batteries in these videos were EG4 WallMount 280Ah Indoor batteries, as confirmed by the owner. The manual's procedure and port depend on the model, and we have not checked which procedure our batteries use.
- The YouTube description of the fix video refers to LifePower4 batteries. The owner identifies the filmed batteries as WallMount 280Ah Indoor, and what worked for us is not established for any other model.
Questions and answers
Which batteries can the EG4 Battery Firmware Adapter update?
EG4's manual lists WallMount Indoor and All Weather models, LL-S, LL-V2 and LifePower4 V2 as compatible, and LL-V1, LifePower4 V1 and GYLL as not compatible.
Can both firmware files be on the adapter at once?
The manual allows the RS485 and RS232 files for one battery model together, but not files for more than one model.
Does EG4 mention resetting the BMS during an RS485 update?
Yes. The current manual includes a note that the BMS must be reset after the Update button is pressed, otherwise the RS485 update will fail.
Sources
Videos this comes from
- How to EG4 Battery Firmware Update | Method That Actually Works – The sequence that worked
- EG4 Battery Firmware Adapter Review & Tutorial (2025) – Firmware Update Made Easy? – Adapter review and our first failed attempts
Related topics
Follow along
New troubleshooting notes and comparisons come from our videos. Subscribe on YouTube or join the Discord. We do not collect email addresses on this site.
Important notice
This page records what the manufacturer publishes and what happened on equipment that TGBATG owns and used, as of the date shown. It describes what we did and saw, not what you should do. It is our experience only. It is not instructions, directions, a design, engineering, electrical or professional advice, and not a recommendation to buy, install, change or repair anything. We are not your engineer, electrician or installer.
Equipment, firmware, apps and manufacturers' instructions change without notice, and results differ with the exact parts, versions, settings and surroundings. What worked or failed for us may not work, or may be unsafe, for you. Updating firmware or changing settings can stop equipment working.
Batteries and mains-voltage electricity can cause serious injury, electric shock, fire and death. Read and follow the manufacturers' current instructions and warnings for every part, follow your local electrical code, and use a licensed professional where the work or permits require one. Contact the manufacturer's support before you change firmware or settings you are not sure about. Do not rely on this page.
We list above some things we did not verify. Even for what we did, we may have made mistakes or left things out. We cannot guarantee that this page is accurate, complete or current, or suitable for your use. It is provided as is, and you use it at your own risk. To the fullest extent the law allows, TGBATG is not responsible for loss, damage or injury that results from anyone relying on it.
If you find an error, please tell us at contactus@tgbatg.com.