Home » Learn About Solar Lighting » Video: How to Troubleshoot Eterno EMS-based Solar Lighting Systems

Educational May 2019

Video: How to Troubleshoot Eterno EMS-based Solar Lighting Systems


This video is a brief troubleshooting tutorial of Sol’s Eterno EMS-based solar lighting systems. You’ll learn how to accurately diagnose and troubleshoot issues related to your solar light.



The tools we’ll be using today include:

  • DC multimeter
  • Battery load tester
  • 1/4” nut driver
  • 7/16” socket wrench
  • Sol battery cabinet key


We created a quick mockup of one of our systems. In order to gain access to the cabinet, you’ll either need a standard Sol battery cabinet key or a 7/16” socket set to remove the bolts on the outside of the door.

Once you gain access to the cabinet, you’ll find:

  • Eterno EMS
  • Fixture harnessing
  • PV harnessing
  • Battery harnessing


The first thing we want to do is check for any damage to the harnessing or damage to the battery itself. Next, we want to check to see the status of the battery fuse, which is hidden behind the protective cap.


Assuming the fuse is intact, next we want to check the indicator lights on the back of the EMS. If it’s a particularly sunny day, sometimes it’s easier to remove the EMS to see them better before continuing with the troubleshooting.

Use a 1/4” nut driver to remove the bolts securing the EMS.


There are three indicator lights on the back of the EMS: green represents the fixture, yellow represents charging, and red represents faults or issues with the battery.


During the daytime, you should only see a yellow light indicating it’s in charge mode. If you don’t, you may have issues with the panel connection, and we’ll show you how to check that in a bit.


If you push the test button, the fixture should turn on and you should see a green indicator light. If it doesn’t, you’ll have a green and red solid indicator light, and that means there’s either a poor connection or you have an issue with the fixture.

Trace connectivity using the fixture harness to the fixture, or if you have another fixture on site that you could swap out that you know is good, test to make sure the fixture is operational.


If either of them are an issue, replace the harnessing or replace the fixture.


If the yellow charge indicator light is not on during the day, you want to check your panel connection. To do so, disconnect the panel and check the open circuit voltage. On each panel, there should be a sticker on the back that tells you the open circuit voltage of the panel. When we test the open circuit voltage, you should expect to get a very similar number to that value.


If you have a good open circuit voltage coming from the panel, it is possible that the EMS needs to be replaced as it is not functioning properly. If you don’t get a good voltage coming from the panel, it may need to be replaced.


So, assuming you have a working EMS with the panels connected and fixture operational, the focus should shift to the batteries. If the red light seems to be flashing, that indicates that either the battery is disconnected, or the voltage of the battery is far below what is expected and may need to be replaced.


If there were any issues with the EMS and there’s been prolonged charging issues, the batteries themselves may be damaged and need to be replaced.


The best way to test the batteries is with a load tester. If the system is over five years old, the batteries may have reached the end of their serviceable life. To properly test the batteries, disconnect them individually from the main harness—this allows you to get a true reading of the battery voltage.


Using the load tester, connect to the battery.

This particular system has a good battery, but if it was poor, you’d see a voltage somewhere between 11 and 12 volts, and when you push the test button, what would happen is the voltage would drop slightly, and if it’s a good battery, it will be maintained (like this one). If the battery has reached the end of its serviceable life, the initial voltage may be between 11 and 12 volts, but when we push the test button, the voltage would drop significantly and continue to drop. This means that the battery can no longer store any energy.


While this load test is particularly more than what the fixture would draw from the batteries, it still gives a good indication of battery health and if they need to be replaced.


If you’ve run through these troubleshooting steps and still haven’t found the issue, or if you require new batteries or replacement parts, please contact us.


There are a lot of different configurations out there so any pictures will be helpful in determining the correct part.

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