Brisbane - Full Backup Tesla model 3 home battery project

[Wattage]

Hi I'm from Brisbane Australia and I'm Planning a Tesla Model 3 home battery project using a "Fronius Primo Gen 24 Plus" hybrid inverter and a Lilygo, running Dala's battery emulator.
I want the setup to be accessed through Home assistant and able to be used for full backup using a Microgrid in the event of a black out.
I have been going for a while with the project and I would like to share my journey from the beginning with the hope that others can learn from any issues i have along the way as the project progresses.

So first up I found a 2 year old Fronius Gen 24 Plus 5.0 inverter on marketplace and ordered a Lilygo from Aliexpress. I made a test box to allow me to communicate with the CAN data from the Tesla battery before purchasing it.

For the test box I used a

- Motorcycle battery

- Lilygo ESP32 board

- A car USBC phone charger for the Lilygo power supply from 12v battery

- A plastic electrical box, power switch and fuse from Jaycar

-And some Jumper pins and wires I had laying around as my X098 plug hadn't arrived yet

I followed Dala's Battery Emulator software installation information using the following page

-

GitHub - dalathegreat/Battery-Emulator: This revolutionary software enables EV battery packs to be easily reused for stationary storage in combination with solar inverters

This revolutionary software enables EV battery packs to be easily reused for stationary storage in combination with solar inverters - dalathegreat/Battery-Emulator

github.com

This was very easy to follow with video instructions and all the information needed to install Arduino software to the computer and flash the battery emulator firmware to the Lilygo board.

Next I was off to the wreckers to test and buy a Tesla Model 3 battery. The battery I purchased was from a 2022 model 3, with 33200k's. It had been sitting at the wrecker for about 2 weeks.

With the test box plugged in I was able to look at overall battery voltage, individual cell voltage, cell voltage deviation, cell temp, overall charges and discharges the battery has had and many other parameters.

When I hooked the test box up all the cells were below the minimum level, but I was told that the battery had only been removed form the car a couple of weeks prior and had photos of the car with 8% battery. Also it was cheap so I took the risk and now I own a Model 3 battery ;-).

NOTE: To read the information from the Tesla battery all that is needed is:
- Lilygo with Battery emulator and 5v power supply
- 12v dc + to pins 8 and 18
- 12v dc - to pin 9
- CAN H to pin 16
- CAN L to pin 15
As stated earlier see - "https://github.com/dalathegreat/Battery-Emulator" for full details.

 

[paulie]

my brain hurts

 

[Dala]

That test-box is the best I've seen so for! Extremely nice work

 

[Wattage]

That test-box is the best I've seen so for! Extremely nice work

Thank you. I was a little worried showing up with my test box, having never seen a Tesla battery in real life before. But it worked really well.

 

[Wattage]

CONTACT!

After a bit of messing around, I was finally able to get the high-voltage contactors to close!

To start, I removed the Penthouse cover using a custom-modified socket that I machined after trying to get one locally to no avail. If you're planning to remove the Penthouse cover yourself, I highly recommend ordering a Torxs Plus socket like this in advance -

https://www.amazon.com/SPECIAL-SOCKET-TESLA-MODEL-PENTHOUSE/dp/B09NB5TRQ5

Once the cover was off, I performed a continuity test on the pyrofuse, and to my excitement, it was still intact!

For the pre-charge capacitor, I used two 500V 390µF capacitors wired in parallel. I salvaged these capacitors, along with a piece of PCB and some contacts, from an old inverter. I then fabricated two terminals to connect the main high-voltage outlet plug to the capacitors.

Additionally, I had to bridge the High Voltage Interlock (HVIL) circuit at all HVI plug receptacles that did not have factory plugs installed. I only had one factory plug, so I had to install jumpers across three HVI plug receptacles. (I believe dual-motor battery packs will have more.) Check the attached images to see where I placed the jumpers.

I also bought a 3D printer as I Found 3D print files for the Lilygo board enclosure and covers for a couple of HVI plug receptacles.
Now to learn how to use a 3D printer
I found the 3D print files at -

https://www.thingiverse.com/thing:6788996

Tesla Model 3/Y covers for battery ports by TheOfficialBatteryMan

SAFETY - Only work on an EV battery in a dead 'contactor open' state and then proceed with caution. Test dead at outputs using an appropriate tester then test that tester on a know power source such as a low voltage battery to ensure a reading of 0v is correct. Only then should HV be worked on...

www.thingiverse.com

 

[Wattage]

So the next issue I had was that the contactors were closing however due to the low cell voltage the contactors were opening again after around 15 seconds.
With the assistance of my local electrician I was able to connect my battery directly to a solar array on my roof to urgently get som voltage into my battery. With the help from Dala I was able to modify the Lilygo programming to allow the contactors to stay closed. As you can see in the photos the I was able to bring the cell voltages up above minimum levels and bring the cell voltage split down to a reasonable figure. I was very pleased that all the cells took a charge.


In addition

- started the battery cradle - the battery is going to sit vertically against the shed wall in the cradle with the power distribution/switch board mounted on the battery penthouse. I have included a photo of a rough life size drawing of the Switch board (just to visualize board size etc.)


So the next issue I had was that the contactors were closing however due to the low cell voltage the contactors were opening again after around 15 seconds.

With the assistance of a local electrician I was able to connect my battery directly to a solar array on my roof and with the help from Dala I was able to modify the lilygo programming to allow the contactors to stay closed. As you can see in the photos the I was able to bring the cell voltages up above minimum levels and bring the cell voltage split down to a reasonable figure. I was very pleased that all the cells took a charge.

I have also
started the battery cradle - the battery is going to sit vertically against the shed wall in the cradle with the power distribution/switch board mounted on the battery penthouse. I have included a photo of a rough life size drawing of the Switch board.
- Ordered 5 circuit breakers, circuit breaker box, and a 12V to 5V step down for the Lilygo
- Printed the Lilygo Din enclosure using Cura

- Started Fusion 360 tutorial so I can design switch board mount, HV covers and capacitor enclosure.

 

[Wattage]

A few steps closer,

- I bought some 0.5mm instrumentation cable for the data cables and 6mm DC power cables. I went with the instrumentation cable because it is a shielded twisted pair and is only a fraction of the price of shielded Cat6 cable, no resistors were required between the Lilygo and inverter.

- I had my electrician hook up my Fronius Primo Gen24 inverter and put 50% charge into my battery. IT WORKS and all the cells are within 3mV.



- I designed and printed my first couple of items on my 3D printer - a housing for my capacitors and some mounts for the power distribution board which will attach to the existing mounts on the penthouse cover. I'm really enjoying Fusion 360 and although I had a few prototypes/fails I think the final products are quite impressive. For the capacitor box I have used a clear polycarbonate cover so the capacitors are contained and can be easily inspected.



- Finished fabricating my battery cradle, paint stripped it and gave it a spray. Who hates paint stripper?

 

[Wattage]

A little more progress, I've been busy on Fusion 360 and the 3D printer designing covers for the battery

- I designed and fitted a back shell cover for the X098 plug and cover for the 12V terminals.

​

- I have all my CB's, bus bars and everything to assemble by power/circuit breaker board.

​

 

[Wattage]

Great progress made with my power/circuit breaker board, still a little neatening up required but almost complete.




- I made the power board out of expanded PVC board due to it's easy workability and both water and fire proof properties. I used a dual pole circuit breaker for the high voltage DC through a negative and positive bus bar (also connected to the capacitors in their enclosure). I also have a CB for Lilygo PWR, X098 power and contactor 12V power.

​

- For the high voltage feed from the battery I cut a hole in the penthouse cover and fitted the 6mm DC cables through a gromet to the contacts in the penthouse. this neatened things up and allowed me to design and make a cover for the high voltage receptacle on the external of the battery.

 

[MeRoBo]

I love to see someone doing this in Brisbane! Are there any hurdles your sparky needed to do to approve this being added to your supply?

 

[Wattage]

I love to see someone doing this in Brisbane! Are there any hurdles your sparky needed to do to approve this being added to your supply?

Thanks mate. No, as long as all the standards are met Energex just needs to know that a LFP battery has been installed. There is no requirement to tell them brands or that it's from an EV.

 

[MeRoBo]

Hey @Wattage, do you have an update of how it is preforming, the final look and if you like the $$ for this system?

 

[Sebastian K.]

Hey,
it’s really inspiring to see how much work and detail has gone into your full backup Tesla Model 3 home battery setup!
I’m currently in the process of connecting the battery to my Fronius inverter, and once the whole setup is working, the next step will be rewiring the PV system and switching over to the Sofar Solar inverter.

I wanted to ask if it would be possible to share the covers for the 12 V terminals and the main HV cover?
I’ve also run the 6 mm DC cables straight through the penthouse cover, and it would be awesome to have my two main HV contacts properly covered so everything stays clean and safe. My battery is currently sitting on the floor, so measuring the HV connectors on the underside with a caliper would honestly be a real pain.

I would be very grateful if you could share the STL files, or even better, the Fusion files.

Thank you very much!

 

[Dala]

I wanted to ask if it would be possible to share the covers for the 12 V terminals and the main HV cover?
I’ve also run the 6 mm DC cables straight through the penthouse cover, and it would be awesome to have my two main HV contacts properly covered so everything stays clean and safe. My battery is currently sitting on the floor, so measuring the HV connectors on the underside with a caliper would honestly be a real pain.

I would be very grateful if you could share the STL files, or even better, the Fusion files.

Some of them are here: https://github.com/dalathegreat/Battery-Emulator/wiki/List-of-3d‐printable-parts#tesla-model-3y

 

[Sebastian K.]

Some of them are here: https://github.com/dalathegreat/Battery-Emulator/wiki/List-of-3d‐printable-parts#tesla-model-3y

Thanks, yes — I already found those and printed them, but the 12 V battery cover and the main HV cover mentioned above are unfortunately not available as STL files.
If anyone has covers for those connectors, I’d really appreciate it!

 

[Kiwi_watt]

Hi @Wattage

I'm planning exactly the same installation. Model 3 55 kWh battery coupled to Fronius Gen24+ inverter, here in New Zealand. Your information is very helpful!

I sourced a Plug & Play controller out of a chap in Perth. This simply packages up the Lilygo into a nice box and adds a few switches and a 12V battery. It looks like a reasonable arrangement. I can get a scrap Tesla battery out of Auckland fairly cheaply.

Are you satisfied so far with your setup? I'm particualrly interested in the whole cell balancing issue and what you've done/are doing to address that.

Cheers

 

[Willuknight]

Do you have a link to the controller kiwi?

Hi @Wattage

I'm planning exactly the same installation. Model 3 55 kWh battery coupled to Fronius Gen24+ inverter, here in New Zealand. Your information is very helpful!

I sourced a Plug & Play controller out of a chap in Perth. This simply packages up the Lilygo into a nice box and adds a few switches and a 12V battery. It looks like a reasonable arrangement. I can get a scrap Tesla battery out of Auckland fairly cheaply.

Are you satisfied so far with your setup? I'm particualrly interested in the whole cell balancing issue and what you've done/are doing to address that.

Cheers

 

[Kiwi_watt]

Tesla Model 3 / Y Battery / Solar Controller | Lithium Power

With the increasing number of Tesla Model 3 and Model Y Batteries becoming available we have put together a controller that allows these large capacity and extremely well constructed packs to be used for stationary battery storage.For international purchase please send an email through to...

www.lithium-power.com.au

 

[Willuknight]

Tesla Model 3 / Y Battery / Solar Controller | Lithium Power

With the increasing number of Tesla Model 3 and Model Y Batteries becoming available we have put together a controller that allows these large capacity and extremely well constructed packs to be used for stationary battery storage.For international purchase please send an email through to...

www.lithium-power.com.au

That is incredible, please let me know how you get on with this, I absolutely want to do the same thing.

 

[Kiwi_watt]

Currently I have achieved this much:
1) Got a battery ready inverter (Fronius Gen 24+) on one of my solar arrays.
2) Obtained the battery controller ex Perth.
3) Found a NZ source for batteries.
4) Obtained permission from my local network provider to make the connection (this was tricky - nobody local has done this, it seems and they were cagey as a result)
5) Planned the installation (battery location, mounting, cable routing - not straightforward in my situation due to the location of the inverter)

Next steps are (I think):
1) Buy battery and have it shipped down to me.
2) Test installation with temporary wiring.
3) If (2) successful - move battery to permanent location (this is quite a task, hence (2))
4) Make permanent connections.
5) Get the whole thing inspected and signed off.

I'll keep this thread updated with progress.

Cheers