Frank's DIY Powerwall

fprumbau

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May 27, 2017
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Hi all,

just beginning here in Germany, near Cologne :D


image_ahwkys.jpg


Frank Prumbaum
 
Note that if cooling is needed when testing you need to have the same cooling on the powerwall :) You test to find weak points.
 
In Germany by now we have temperatures of 25-30C, it's summer finally(!), so in my room it is now very warm, too. Some of my cells have very low voltage, so I do have to 'start' them using some loaded cells. I leave the room often for several hours; some days ago when I got back, a cell was so hot I burned my hand. I do not want to risk a fire and I do not wan't to throw cells away only because there voltage is low. So I opt for the fan, running at a very moderate speed though (12V fan driven by NIMH 6-7V).

@daromer So, if the cell gets really hot (>55C), I will not add them to the powerwall. If they are somewhat good (i.e. if they keep their voltage), I will save them for laptop/powerbank/flashlight usage. Mostly, though, I'll send them on their final way...
 
Still i would say you should not run a fan on them for testing. If you are afraid of fire you need to watch the cells and or have them somewhere else.

As i said you do want to see what happens to the cell in the test and if you have the fan on them you could potentially remove alot of heat without any issues with just a slow moving fan :) Dont take me wrong on this but its all about safety in the end and the test can be done in controlled way meanwhile the actual use later on you will most likely now monitor in same sense.

If the heating of the cells is a big issue add extra temperature monitoring to it. I did a video on how you can add it easily on the Opus.
 
fprumbau said:
Hi all,

just beginning here in Germany, near Cologne :D


image_ahwkys.jpg


Frank Prumbaum

Hi Frank,

viel Erfolg und Gre aus Braunschweig :). Check out my project here...

Btw, if your cells get hot during testing, reducing the charging rate is a much better idea than using a fan for cooling. The fan doesn't stop a chemical reaction inside, I guess, and if a cell catches fire, the fan will burn, too... In addition, the OPUS charger have a built-in temp sensor and should turn off a cell if it's getting too hot (never tested that, though). I also had some cells that went very hot during charging (with both OPUS charger and TP4056 charging PCB) and after reducing the charge current from 1A to 500mA or lower, they cooled down again.

Have sun!
Oliver
 
I'm testing batteries and running the powerwall in a badly insulated room under the roof, it's more than 30c inside since a few days and no problem, batteries are a bit hotter but nothing too hot to be handled, if it occur Idump the cells.

I revive a lot of 0v or 0.01v cells, most of them are in good conditions, but don't take risk, hot cells are dangerous AND don't hold properly their charge so it's ineffective for storage in addition to the risk.
Reducing charging current is a better option than cooling likefprumbausaid but you want to test the cells at least with a bit more than you final use, that's why you tests stuffs, not just for capacity but for safety and long life of your build too.

Think twice before putting a bad cell in your packs, does it worth the risk to rebuild it in two months because of 2 or 3 bads cells ?
 
OK, I have dropped the cooling fan and remain inside the room to monitor dangerous heating in the
first 10 minutes. I go with 500mA charge instead, cause the load I want to load on the individual cell
should not surpass 500mA in loading / discharging.

The way I placed the chargers will not allow a dangerous fire to develop.

But for now I have a question, what do I have to do to have myself
'certified' :) , earning this nice star? I post updates every day or so.

I plan on a powerwall of about 50kWh or more, so I will not start building it some months or so.

I plan to replace my Computer-UPS in another project
with a self build ( as of now thinking of bying a ClaytonPower G3 2324, so a 24V system) and
using all my not-so-good-cells ( <1800 mAh). Any thoughts / suggestions about this?
 
The star as in the count cell list? The star is when you have a verified running wall.

Cologne? Close to The Post Apocalyptic Inventor on Youtube? :)
 
A star is earned by proving you are using Recycled 18650 cells & testing in the 'accepted' manner. Cells don't nessassarly need to be in service - just saved so to speak :)
 
OK, thank you, I'll update my cellcount and will document my progress in building my 'first' device.
I have pv already (SMA) and want to sell less and use more power :)

( I saw you using SMA, too )

As for the 'accepted' manner, I have 2 Imax B6AC v2 (which I'm using testing and loading the larger modules (as of now only bycicle 7s modules I do not want to take apart) and
two Opus chargers, one Bc-4000 expert. For now, I don't know the path to take, either get other 7s modules coming in a perfect-to-reuse packing of 288wh or / and having my own-build modules (very much looking like yours).

For that I would be interested in using a SMA Sunny-Island (I read in works with your bms, too).

Have to mention I saw some ( a lot ) of Jehu's videos. In one of them he mentioned your project and the ONE fault using the best cells for module one, the next best for module too... I agree to him, and plan to select my module with 'take the best cell and the worst alternatingly', so the modules will should not different only by a very small margin.

I also was very entertained watching all your bus-bar-videos. I plan to take the 4cellx80cell / 100cell approach, but plan to use loudspeaker wire, tinned already.
https://www.amazon.de/Supra-Cable-f...r=1-1&keywords=flaches+lautsprecherkabel+6mm²
This should be very easy to solder. Furthermore I do not plan to twist it. I hope the exchange of single defect cells will be possible...
And I plan to use the 4x5 cell spacers preferably. I do have 400 single ones already, but I do not like the process of putting them together :)
 
@The-J-Man Oh, vielen Dank!

For now just spending some money ;-)

Trying to do what everyone else is trying, too. Doing everything as showed - but better :-D
 
Thank you for pointing me to Electrodacus an his SBMS project. Even if its pretty useless to me (living in an apartment so no solar panels (yet ;) ) ) and I dont understand everything (noob), I somehow like it.

Best wishes for your Powerwall build!
 
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