Dutch powerwall; first test-building project

Dear DIY-builders,

Thank you all for sharing all the information. I got alot of inspiration from all the nice projects on this forum.

4 years ago I started driving a electric scooter. I started with lead-acid batteries and switched to Lithium-Ion battery-pack. These stock-packs from "Emco" were not very good, so I needed to have good new battery-pack. I met this incredibly helpfull guy on a dutch forum tweaker.netcalled "Flippy". He helped me build 2 new packs with new Panasonic cells and brand new Tiny-bms's. Now I can drive more then 150 km on 2 packs!

But all of this got me excited to build my own powerwall. The solarpannels on my roof provide me with 4500kWh in a year. The exces kWh I give back to the grid, but I wanted to experiment to store that energy. So I wanted to start with a test-project. Goal was to start-off by making my own battery-pack that can provide me with 240V AC. This journey I like to share with you guys:

The scooterdealer was so nice to provide me with 7 old battery packs (196 cells per pack) for freeto start. First thing was to dismantle these packs:




Then I tested all the cell resulting in about 800 of 1400 cells that were good enough to get a nice second life:




Then the buiding started:




And the spotwelding:







Then connecting everything together including the BMS (tiny-bms from energus):










And finaly, after many testing closing the wooden case:
















In the end its running. The BMS struggles to keep the cells balanced but its working and provides me with about 5kWh of energy. I use my old scootercharger to charge the cells.
This was my first test run and now i am planning how to make a new powerwall that is not standalone.

Nice ... all spotwelded ... clean pack.
No celllevel fusing i presume ?

And welcome ...

cateye22 said:

In the end its running. The BMS struggles to keep the cells balanced but its working and provides me with about 5kWh of energy. I use my old scootercharger to charge the cells.
This was my first test run and now i am planning how to make a new powerwall that is not standalone.

Click to expand...

Why is it struggling? Weren't the cells fully tested (also including a rest period to detect self-dischargers) before assembly?

Now you know the amount of work required to build everything and you can get a pretty good idea of overall costs.

That's a lot of tapcon tape

How come you went with one large pack? Looks like 1 pack to me, but I could be blind (wouldn't be the first time)

Korishan said:

....
That's a lot of tapcon tape

Click to expand...

Tapcon tape ? tapcon tape ?? tapcon tape ??? googled it ... no such thing ...

I think you mean Kapton tape, right?

wim said:

Korishan said:

....
That's a lot of tapcon tape

Click to expand...

Tapcon tape ? tapcon tape ?? tapcon tape ??? googled it ... no such thing ...

I think you mean Kapton tape, right?

Click to expand...

Meh, Kapton sounds too much like Krypton

@ Wim. All is spotwelded. My next project will be with new cells and as far as i read on several forums soldering is not very good for the cells.
@ Korishan; Yes its Kapton-tape, It keeps me safe from accidently leave a screwdriver on my pack . And yes it is one pack (14s50p). The fault I made was not leaving the cells to detect self-dischargers. I was to eager building my test-powerwall. The 5th serie cells is around 70mV behind the rest from the beginning. I will try to manually charge it and will see how that works out.

My next project will be a new powerwall with new cells. I want it to run ongrid and offgrid in case of an blackout or flood (I live 4 meters below sealevel). The powerwall must run from the topfloor so it keeps running (charing from solar and providing 240V AC) during a flood . In this emergency the powerwall must be disconnected from the electric wiring through the house and run on his own output (like my test-powerwall)

I have 21 solarpannels on my roof and have a sunnyboy 5000TL-21. I have 2 strings on it; one providing 350V and the second 261V. The solarinverter needs power from the grid in order to run.

Do you guys have some good ideas for a powerwall setup that can switch between ongrid and offgrid? And can my sunnyboy be part of this setup?

Contactors can help a lot in the switching department. daromer has a few videos about them. You can either trigger them manually, thru a timer (mcu or dial), or if source is available or not.
And they switch really fast, <50ms, so your devices shouldn't complain too much about it.

The Victron Multi's should be able to do that for you. A Multi will create a local net when the grid shuts down, and the Sunny Boy should keep on detecting the power from the Victron Multi. But it's af bit complicated setup, and you should seek advice from an experienced local installer.

You either need an off grid inverter and a switch to switch between that inverter and your grid or extend yourSunny boy with SMAs sunny boy storage or buy a hybrid inverter that does it all. I went (am going) for the first route.