The overload and low battery indicators on the Multiplus II inverter are illuminated. According to the manual, this indicates that “the inverter is switched off due to excess ripple voltage on the battery terminals.”
The installation has been operational for 3.5 months without issues until now. Previously, there was an alarm on the Lite eTower batteries (two units of 5kWh each). However, the following day, the alarm cleared on its own. We pressed the reset button for six seconds, and since then, the batteries have remained silent. All the green LED indicators on the batteries are lit, signifying that they are fully charged.
Here are some specifications of the installation:
System Type: Hybrid system
Capacity: 6 panels, each 545W
Inverter Model: Multiplus II 48/3000/35-32
Battery Model: FREEDOM WON eTower E5000 5kWh 52V LiFePO4 Battery
Battery Cables: Standard DC cables (1.8m long, 35mm² single core) with M6 terminal lugs on one end.
Additional Modifications: We attached additional M6 terminal lugs ourselves to connect the inverter with the busbar.
Could you please advise on the potential causes and solutions for the issue we are facing?
The DC cables connecting the panels to the component board are 6mm in diameter and multi-stranded.
The DC cables between the batteries, inverter and charge controller are 35mm in diameter and also multi-stranded.
Use a meter set to ac and measure the voltage from battery terminal to the inverter battery terminal to get an idea of the ripple there.
Is the ripple bad under certain specific loads? Or just when you try start up?
A small correction on set up. Your take off from the battery bank should be positive on one and negative off the other.
If you used the 35mm² that can with the FW then it will be your crimp that needs to be checked. What crimper do you have?
The length run from.the inverter to the bank is definitely longer than 2m. So probably should have sized up from there.
If he used the ones that come with the FW batteries then they are 35mm².
The distance though looks longer than the 2-5 m return length. So probably should be slightly larger gauge.
Lenses on cameras can distort things. Jolien confirmed their size.
They are the ones that comes in the box with the FW eTowers, there would have been no need to purchase any cable. One side it already crimped too. You just add your own lugs on the other.
Indeed, the 35mm² DC cables came with the FW batteries.
Each battery was supplied with: “Standard DC cables, 1.8m long, single-core 35mm² with M6 terminal lugs on one end, red for positive and black for negative.”
Since we could connect both batteries using the metal plates (also provided with the FW), we used the remaining cables to connect the charge controller, inverter and busbar.
Most of the plugs were attached by ourselves in a very old-fashioned way, hammering them until they were so tight that they couldn’t be pulled loose. So, I would be surprised if that were the issue, but it’s still possible.
Currently, I’m not on-site to check the exact problem myself. Communication has been a bit challenging, I have no response so far, but I’ll provide an update as soon as I have more information.
So LX, your advice is to use a multimeter to measure the ripple voltage and check how large it is when the issue occurs. What conclusions could we draw from this? Additionally, I’ll recommend checking if the ring terminal connectors are still securely fastened.
@Ludo
The battery cables that come with the freedom won batteries are the correct cables. I have used them. The only issue is they are only provided with a lug on one side.
@Jolien
You need a proper hydraulic crimper for your lugs. There is no debate there. That is where the ripple comes from. That will be a high resistance connection.
