We’re working on a little project, the details of which will be revealed in due course.
A few months ago we installed a couple of solar systems: each one consisting of a 5kW Solis S6 inverter, Freedom Won eTower 5kWh battery and ten Canadian Solar 585W bifacial Evo 2 panels.
They started off working steadily, but not hard – exterior lighting and light domestic use. One installation works a little harded as it is connected to a borehole with a 2.5kW operating load for an hour or so most days.
The more lightly loaded installation started having intermittent battery trips, usually in the afternoon. Then a couple of weeks later the unit running the borehole started having the same problem, but on a daily basis and eventually multiple times per day but at fairly consistent times: early morning, early afternoon and early evening.
To explain “battery trip” the inverter would remain online, at least in daytime while the panels were providing power, but the battery would go offline and require a poke in the reset hole to bring it back online. The inverter would initially send a “Batt_Comm_FAIL” error and after an hour or two followup with a “NO-Battery” notification.
We tried a few simple tests: checking the CANBUS cable between battery and inverter for pinouts, taking the cable out of the trunking to eliminate electrical interference, and updating inverter firmware. The Freedom Won eTower battery is not capable of being updated over the internet or by the owner.
The batteries were bought online from Voltex around September 2025, and the serial numbers indicate they were manufactured in 2023, so had been sitting in a warehouse for a couple of years already. A cursory search suggests Freedom Won started selling eTowers in 2021.
Whilst troubleshooting I found some discrepancies in documentation and hardware depending which search results you find. Different inverter manufacturers use different pin combinations on the RJ45 CANBUS sockets, and Freedom Won include two cable types with the battery to suit the most common. Some online documentation has contradictory pin or cable combinations: approach with caution.
To cut a long story short: the standard ethernet cable included with the inverter works with the eTower battery.
Accepting that this was not something we could solve ourselves I opened support tickets with Freedom Won, and (on request) they were kind enough to provide ex-works a USB to RJ11/RS232 cable that was collected by my friendly cross-border transporter.
A brief intermission while waiting for a break from the day job and we made an appointment with a Freedom Won technician to update battery firmware and check the settings to restore normal operation. To do this they need you to install Teamviewer and work remotely: so you need a decent internet connection.
They will download PBMS Tools – it seems Freedom Won eTowers use Pace Battery Management Systems – and connect to the battery. The default password is available online using intuitive search terms.
Disclaimer: Poking around in the BMS on your own may damage or brick your battery and or system.
Watching the process I could see them download and install the latest battery/BMS firmware, and check the cell voltages. It looked like some cells had significantly different voltages to others, indicating a balancing issue.
That was the easy one… it has been running constantly for about a month now without trips or other issues.
The other system had gone so deep into self-protection* that it would not stay on for any extended period: we managed to keep it up long enough for technician to install the firmware, instruct a round of battery balancing and disconnect.
* the BMS kept shutting down the battery, so the inverter was not sending electricity to charge it, and the person staying in the building kept resetting the battery to try and get power…
The technician said everything was good, but everything was not good: the inverter was still not detecting the battery and so was not sending power to it to charge: despite the BMS saying the charging circuit was closed.
At this point the technician stopped responding on WhatsApp so it was over to the civil engineer to find a solution.
It didn’t take too many braincells to workout that the alarms relate to low pack voltage (the whole battery), low cell voltage (the individual cell packs), and low state of charge. Bonus points for the indication that the battery was in a protection state due to low cell voltages.
A rummage through the settings and I found the menus with voltage settings:
These are intended to prevent over-discharge of the battery and cells, so when the battery goes into under-voltage protection (UVP) mode the BMS disconnects the battery terminals from the cells, and so can neither give or receive power.
Whilst the pack voltage was above the Pack UVP most of the individual cells were below the Cell UVP.
After taking screenshots of the default settings I reduced the Cell UVP to 2.8V, and was rewarded with some clicks and indications of life from battery and inverter.
I left the system charging and returned later to reset to defaults.
After a couple of months I am pleased to report that the battery trips are a thing of the past, and I have since become a solar PV nerd obsessed with charging, discharging, and weather.
It’s not clear what was causing the original trips as they were occurring mostly in daytime or early evening when voltages should have been sufficient – unless some cells were so unbalanced they were hitting under- or over-voltage limits and triggering the protection mode.