When I left you in Part 5 of the Powerwall series, I said I was done. That was the case, I don’t think I will ever be done. Part 6 is a testament to all the bits and pieces I have done since to get a fully configured Powerwall that I am happy with.

Batrium and Goodwe CANbus Communications Issue

In Part 5, I mentioned and had a video of the problem I was having with the CANbus comms link between the battery management system (BMS) and the inverter. In a nutshell, during discharge, I was seeing the inverter constantly stop discharging from the battery. It stopped discharging then started at random intervals. Now, I spent a lot of time trying to fault find this. I even went to the extent of sniffing the Batrium CANbus comms and learning and converting the outputs so I could see if that was the problem. As it turns out, it was not the CAN comms causing these symptoms.

After two months of trying different settings and combinations on both the Batrium BMS and the Goodwe Inverter, I finally contacted Goodwe again and asked if I could purchase a new Goodwe ‘GM1000’ Smart Meter. The support guys here in Australia sent me one out straight away via TNT Express without charge. It’s kinda like they knew it could have a fault. No questions asked…(Thanks Goodwe!) I was very skeptical that this would fix the issue. However, I did get my electrician over and we installed the new one. Low and behold the inverter could now track the battery usage better and no dropouts on the DC battery side at all! If only I had tried this first!

A battery Upgrade

As it turns out, the 9-10 kW 18650 pack I spent so much time on is not enough to give me coverage throughout the afternoon and the night. I went very conservative with my usable battery voltages and on average my battery was reaching its bottom voltage around 3 or 4 am. I was ok with that at first as the power usage between then and when the solar kicks in were minimal. However, as luck would have it, an opportunity presented itself and I was able to get a hold of 16 x LifePo4 prismatic cells. These suckers are around the 400Ah mark in capacity and were used in a trial bus project which by all reports did not progress past a trial. Not only was the added capacity what I needed, but the LifePo4 chemistry is much safer than the 18650 lithium cells currently in service.

Bus Bars

With new cells come new busbars. I wish it had been this easy from the start. Measure the distance between the lugs, cut and drill some super thick copper and voila, bus bars for days! If only it were that simple, hey! As it turns out, these cells actually swell slightly, and having a solid bus bar can cause issues at the lugs. It is suggested that you use some kind of flexible busbar so that when the cells swell slightly, the pressure is not on the terminal. I am yet to source some flexible links.

Done? Probably not…

So what do you think? after all that I don’t think I’ll ever actually be done with this Powerwall build, however with the fixes and additions, I am hoping that it is more peace of mind and only periodic maintenance. Onto bigger and better projects now. Bring on the Electric vehicle build!

If you missed the first parts of the build.

Part 1 – Recycling batteries
Part 2 – Building Packs
Part 3 – Fusing and cell protection
Part 4 – That’s a wrap
Part 5 – Finally Finished (Kinda)

Battery Connection

The first item on the agenda after the last post was to connect the batteries to the inverter. This was super simple. A couple of lugs later and voila done! The only issue I ran into was that the 35mm2 lugs I used would not fit through the cable glands properly. Lesson learned, terminate the cable after feeding through the cable gland. If you’re running a GW5048D-ES then it suggests 25mm2 cable which would probably fit with the lug through the gland, but I decided on a heavier gauge cable. Also, try and keep the cable run short to minimize any voltage loss on the cable. You can calculate this but at less than a meter, I assume the cable loss would be negligible.

Batrium CANbus to Inverter Connection

This had me stumped for a while, however, we eventually got through it. The GW5048D-ES came with a dedicated BMS cable. This cable at one end only had 3 pins terminated. After a bit of investigation, I found that the Blue pin = CAN-H, White/Blue = CAN-L, and the Orange is GND. In the image gallery below you can see the extract from the manual. Now I am no expert on the CANbus protocol but it seems that having a 120ohm resistor on each end is pretty important. The Batrium Watchmon 4 came with the resistor installed and I was able to find some clear instructions on the Batrium website for which pins to connect to.

At first, I did not connect the GND pin, It still seemed to work, however, I eventually connected it with no significant change in performance. Also of note is that I connected the BMS cable from the BMS port on the inverter to the CAN/H/L pins on the Watchmon. See the Gallery below for a few pics of connection.

(Almost) A complete Failure

After connecting the CANbus cabling, I attempted to configure the Batrium software to talk to the Inverter. As it turns out the only way I could get Batrium to talk to the inverter was in the integration settings in Batrium and select the “Project Lychee” integration. This integration mimics an LG RESU 6.4 battery. Thus on the Inverter and inside the PV Master App (Goodwe Configuration Tool) I had to select the LG RESU 6.4EX battery type. I was then able to confirm in Batrium that CAN comms were working. What you need to look for is that batrium transmits and receives.

Now that I had Batrium Communicating with the inverter, surely it would just be a few tweaks of Batrium?… How wrong I was. At first, all looked good, the charge cycle completed at the values I had set in Batrium and all was well. I started running into issues during the discharge cycle. The inverter could not make up its mind if it wanted to discharge or sit at idle. As you can see from the video below, keeping an eye on the “Shunt A” value. That is what is happening on the BMS shunt.

So where am I at now?

So after much back and forth with both the Batrium support team and Goodwe, no one can or wants to help me. I paid $85 for Batrium support in which they basically told me it was an inverter issue and Goodwe told me to use an approved battery. Boooo! So, for now, it looks like the remote integration is a no go. Not all is lost though, the inverter actually has a “self Define” battery option. This option is designed for Lead Acid batteries and has a few settings that can be configured. Such as Battery Capacity, Voltage Charge Target (56.7v in my case), Charge/Discharge Current (20A/20A to test.) and some SOC protect percentages. I have since been using these settings for a few days now with no issues. The inverter charges nicely and cuts of at set voltage. I am yet to run the battery down to test the SOC protect. That is next on my list.

If you missed the first parts of the build.

Part 1 – Recycling batteries
Part 2 – Building Packs
Part 3 – Fusing and cell protection
Part 4 – That’s a wrap