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New EG4 - 3000 EHV - Battery Back Feeding Power to Solar Panels at Night

 
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Last Post by Hanzi 1 month ago
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Posts: 9
 Hanzi
Topic starter
January 29, 2025 7:25 am
(@hanzi)
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Joined: 1 month ago

I recently installed an EG4 3000EHV-48 inverter and have observed some unexpected behavior. During nighttime, with no ambient light due to cloud cover, I measured approximately 27.3 volts DC across the PV input connections. This measurement was taken after disconnecting the PV wires from the inverter, ensuring that the voltage was present directly at the PV input terminals. Currently, only a LiFePower4 51V battery is connected; the system is not connected to grid power, nor is there any load.

Additionally, I've noticed that the inverter's fans have been running continuously throughout the night, despite the absence of solar input and active loads.

Questions:

  1. Is it typical to observe voltage across the PV input terminals at night under these conditions?
  2. Could this residual voltage be causing the fans to operate continuously?
  3. Has anyone else experienced similar behavior with this inverter model?

I would appreciate any insights or suggestions from those familiar with the EG4 3000EHV-48 inverter.

Topic Tags
EG4 3000EHV-48 PV Input Voltage Inverter Fan Operation Nighttime Behavior Backfeeding
15 Replies
Eric
Posts: 144
 Eric
January 29, 2025 6:43 pm
(@eric)
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Joined: 5 months ago

It’s probably due to residual energy. Have you tried turning it on or leaving it on to see if the energy drains out?

Also, If the PV is connected, it will show some voltage, whether it’s day or night.

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 Hanzi
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January 29, 2025 9:16 pm
Reply toEricEric

@eric - As background, I received and installed the all-in-one inverter and LiFePower4 battery yesterday afternoon. The solar panels were connected to the inverter at night when there was no PV generation. I noticed the fans were running as if charging, so I measured the PV connections at the inverter and observed a voltage of 27.3 VDC. After disconnecting the PV connections, I measured the solar arrays voltage, which was 0 VDC. Then, I measured the DC voltage across the open PV connections on the inverter and still found 27.3 VDC between the (+) and (-) terminals. I turned the inverter off and back on, but the voltage remained. Not sure why there would be any voltage output on PV inputs.

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Eric
 Eric
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Eric - Facebook
January 30, 2025 10:02 pm
Reply toHanzi
Eric

@hanzi When you measured the PV input at the inverter, were the batteries still connected? If so, try disconnecting the battery power and measuring again. There may be some residual power leaking from another source.

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 Hanzi
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January 31, 2025 6:03 am
Reply toEricEric
Eric

@eric- results of some testing I did tonight.

PV Input Voltage Testing

The PV input voltage refers to the DC voltage measured across the inverter's PV inputs.

Test 1: Inverter ON, Batteries Connected, Solar Panels Connected, Loads Connected

  • Measured 18.1 VDC at PV inputs (0 VAC).
  • Turned inverter OFF → Measured 0.9 VDC (0 VAC) at PV inputs.

Test 2: Solar Panels Disconnected

  • Measured 0.9 VDC (0 VAC) across the positive and negative solar panel wires (not the PV input terminals).

Test 3: Solar Panels Reconnected, Inverter ON

  • Turned inverter ON (same connections as Test 1).
  • After startup beep, PV input voltage measured 17.5 VDC.
  • Turned inverter OFF while measuring → PV input voltage gradually dropped from 17.5 VDC to 0.9 VDC (solar panel voltage) as the fan stopped and the display turned off.
  • Turned inverter ON → PV input voltage ramped back up to 17.5 VDC at the startup beep.

Test 4: Inverter OFF, Battery & Loads Disconnected

  • PV input voltage measured 0.9 VDC (solar panel voltage).
  • Reconnected the battery (inverter still OFF) → Measured 6.3 VDC at PV inputs.
  • Turned inverter ON → PV input voltage increased to 17.5 VDC at the startup beep.
  • Reconnected loads → No change in PV input voltage.

Observations from Previous Testing

  • Voltage is present at the PV inputs whether the solar panel wires are connected or not.
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Eric
 Eric
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Eric - Facebook
February 4, 2025 10:16 pm
Reply toHanzi
Eric
Eric

@hanzi Thank you for this! Let me share this with our team and I will update you as soon as we have an answer.

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Eric
 Eric
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February 5, 2025 9:15 pm
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Eric
Eric

@hanzi The low voltage you’re seeing on the PV inputs is due to the PV and batteries sharing the same DC bus. As a result, there will be very little voltage present on the PV input.

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 Hanzi
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February 6, 2025 1:32 am
Reply toEricEric
Eric
Eric

@eric thank you for the response. I believe there's a capacitor that gradually charges up to and discharges the 17-18 VDC when the inverter is turned on or off. At night, the panels have a high resistance, so that voltage isn’t technically backfeeding current into them. Thanks again for looking into it.

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Joel Brodeur
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 Joel Brodeur
January 31, 2025 1:58 pm
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Just curious, when you are testing the voltage at the PV inputs (neg lead to neg input pos lead to pos input) are you getting positive or negative DC reading?

Where is your NG bond?

Are you getting any stray voltage to ground?

 

Sometimes the easiest solution is the best solution.
Sometimes not.

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 Hanzi
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January 31, 2025 5:50 pm
Reply toJoel BrodeurJoel Brodeur

@joel-brodeur - I have been testing the inputs with correct polarity (red + / black -), and reversing the polarity does result in a negative DC voltage reading. The voltage present is confirmed to be DC, as AC measurements show 0 volts. This voltage persists regardless of whether loads are connected. Currently, there is no neutral-to-ground or earth ground bond, as I am still in the process of wiring everything. These observations are from initial out-of-the-box testing of the battery, inverter, and solar panels.

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Joel Brodeur
 Joel Brodeur
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January 31, 2025 5:55 pm
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Joel Brodeur

@hanzi I had similar experience while commissioning a 6000XP, as soon I got an Earth Ground and a NG ground at the panel (not the programmable NG bond in the inverter) everything cleared up for me.

As to why I am not certain.

 

Sometimes the easiest solution is the best solution.
Sometimes not.

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 Hanzi
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January 31, 2025 6:03 pm
Reply toJoel BrodeurJoel Brodeur
Joel Brodeur

@joel-brodeur - Interesting. You'd think there'd be blocking diodes or MOSFETs protecting the inputs to stop any current backflow. Both would cause small voltage drops, though. Best bet is to find where the feedback's coming from and fix it at the source.

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 Hanzi
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February 1, 2025 2:34 am
Reply toJoel BrodeurJoel Brodeur
Joel Brodeur

@joel-brodeur - I connected the AC input from the inverter to my house's grid-tied panel, which has a neutral-ground (NG) bond (with No AC loads connected to the inverter). There was no change; the voltage is still present. For testing purposes, the AC output is temporarily connected to a double-gang outlet box, so the AC output side from the inverter is not NG bonded, only the AC input side. Still waiting to hear back from Signature Solar on this one.

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Joel Brodeur
 Joel Brodeur
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February 1, 2025 3:11 am
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Joel Brodeur
Joel Brodeur

@hanzi Beyond my experience but please keep us posted.

Sometimes the easiest solution is the best solution.
Sometimes not.

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 Hanzi
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February 1, 2025 3:51 am
Reply toJoel BrodeurJoel Brodeur
Joel Brodeur
Joel Brodeur

@joel-brodeur will do once I get some answers.

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 Hanzi
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February 6, 2025 1:34 am
Reply toHanzi
Joel Brodeur
Joel Brodeur
Joel Brodeur

Response from EG4, similar to Signature Solar Tech Support: "The low voltage you’re seeing on the PV inputs is due to the PV and batteries sharing the same DC bus. As a result, there will be very little voltage present on the PV input."

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Topic Tags:  EG4 3000EHV-48 (1) , PV Input Voltage (1) , Inverter Fan Operation (1) , Nighttime Behavior (1) , Backfeeding (1) ,
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