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Creation and building of the of the znbr2 cell
#1
Hi ya all.
This project started several weeks ago and i have good hoops for a good ending, if no good ending: bad luck, waste of money but a LOT of fun.
A forum member brought this to our attention, and i decided to experiment further with it:
https://secondlifestorage.com/showthread.php?tid=8557

In short
Those cells can not give a high c number, but can pack a lot of power
There are 2 or three claims of 2c, and 100 claims under the 0.5c
There are theories (i found one real test paper)of mixing a chemical with it, that could bump up the c, but the shelf life will be drastically reduced.
For example: with iron oxide it would be 1c but 1500 cycles.
Those cells could have a cycle life well over 10.000 if we stick only on ZnBr.
The first tests where depleting it to 0v and really overcharging, it seems it did no harm.
I will create a separate thread for this and put a link to the test results over here.
Cause this is a lot of material....

My cell surface is 35cm2 at a discharge/charge rate of 20-40mah per cm2.
Would imply: 0.7-1.4ah but for 20 hours long. 
What my cells theoretically could store = ~14 to 28A????? at 1.82v

I think this is the best way to build a proper testing cell for some chemistries, in my case the znbr2 cell, before i take it further for a ess: lets build and test.
Test results will be in a separate thread.

The beginnings of the build are in the link mentioned above
The used materials can withstand a broad variety of chemicals.

This is the cheapest way: cutting up a jerry can, softening the hdpe in the oven at a preheated oven at ~100C molding it warm into a jig, soldering the case close.

What is very important, to get your cell case closed.
Before you put in oasis, iron the edges flat.
One wrong and one the proper way in a picture:




You really want to see the edges of the hdpe sticking to the baking paper.
Don't move your iron, let it float flat, incase your iron has those steam holes in it.
You really want to have a flat level and strait surface on your cell walls, the melted and thus extra stuff we will get back to that.
But make sure its flat.....
DO THIS IN A VENTILATED AREA!!!!

Work in pairs and a flat bottom weight, meaning: work on one let the other cool down under weight.
When one is "flattened out" the other one is cool and rigid enough to put aside.

Prepare/cut your carbon foil, your graphite foil and oasis(rockwool can be a better option btw)
Don't mind if the oasis is oversized or thicker, it's better!



Iron in total 4 pieces carbon foil with one piece of graphite foil together, one piece at a time! use your baking paper so you wont fuck up your (wifes) iron.
180 to 190 celsius is advised, it will take a couple of seconds to let the heat sink in to the hdpe, you will feel after a couple of times.

DO THIS IN A VENTILATED AREA!!!!

As last you iron the graphite foil on it
Made no pictures sorry, forgot.

Now remember i told you to flatten out the cases? cut one side the inner rim out, so you will create a bevel base:


Press this in your oversized oasis:



Cut to size with a good long and thin knife, like a fish knife.

Now the thicker part:

Press it well into your cell casing, with help of a piece of wood, press hard but you don't have to stand on it.
Cut the excess materials, that's why no stanley knife but a fish knife, not to thin and sharp.
Dont matter if there is one mm still sticking out. that is better than 1 mm to little!!!

Oke get your sheets of heat welded carbon and graphite foil.
Place one at a side of your cell case, baking paper over it and the iron.
It should look like this, that's why the first step was to flatten out your case!!!!

Fuck up two or five...but then you have the feeling!
Oke now we can go difficult or easy...it is for testing lets do it the easy way.

Get some alu tape(conductive type!) and put your wires on.

When charging, the first or the 10.000st time, positive is always down and negative always up! This is the influence of gravity on the ZnBr cell
WARNING                      WARNING                         WARNING


THIS IS NO JOKE, USE IN A WELL VENTILATED AREA.
If your nose is getting irritated just like with regular acid, go outside, breath in via mouth and out via nose.
Cover all with lids and vent better before proceed!

Measure every thing as best as you can, a "normal" kitchen whitening scale won't suffice at those small amounts.
100 ml distilled or demineralized water and add 40 gr of znbr2.
Stir every half hour for three hours, don't mind the heat, it is not much.


Yes it is still not clear, some manufacturers throw some waste into it, no panic, just let it settle 24 hours, it will sink down.
After 24 hours than you will have a transcuralend fluid clear as water. dont let the sediment come back into your solution.

After just 12 hours i got this:

You will see some sediment on the glass walls, i scratch some away with the spatula.
Clear as water:


The sediment is some cheap undissolvable salt, that has nothing to do with the zn or br.
Bromine salt is gained from the oceans waters, i thought, so i suspect its a salt or mineral residue that is really hard to get out.

Oke drill two holes in your casings, don't go to deep....only casing, you could prep this before you put in the oasis.
Put your two syringes into the holes, fill one syringe with your electrolyte(znbr2 solution)
And let the law of communicating vessels do its job!


Take time! can take up to 24 hour before complete full...
When they are full

You close the holes with a piece of hdpe, let it melt into the hole and make sure its really closed.

As a test, you could squeeze softly in the cell, if any dripping is occuring melt it to close it.
Its a feeling when both surface areas are connected, your solder iron will start sliding.

Hook it up to your charger and let the initial charge begin. My hand is in front of the display so you can see i am still testing cell 1 and 2 with leds.


Again: When charging, the first or the 10.000st time, positive is always down and negative always up! This is the influence of gravity on the ZnBr cell
Because this is a global site: I use the metric system, to avoid (calculation) mistakes from my side.

I think this covers everything of my second attempt to make test cells.
I also don't think the basic design will change much, only one ore two double in height and one or two in surface area.
By this time i run out of my ZnBr2, depending on the numbers of the experiments i will A: buy nothing more or B:in doubt buy 500 grams or C: convinced: buy 25 kilo(forum member will benefit if they want to try ofcourse!)
Best
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#2
(02-25-2020, 05:57 PM)100kwh-hunter Wrote: Hi ya all.
This project started several weeks ago and i have good hoops for a good ending, if no good ending: bad luck, waste of money but a LOT of fun.
A forum member brought this to our attention, and i decided to experiment further with it:
Will paste a link.

I think this is the way to build a proper testing cell for some chemistries, in my case the znbr2 cell, before i take it further for a ess: lets build and test.
Test results will be in a separate thread.
.....

Dinner is waiting, i will finish this post tomorrow...also links and grammatically wise, ect
Best

Talking about a detailed building instruction Smile so cool! I will follow with great interest. The scientific papers on this seem to be promising!
Perhaps to measure capacity of a battery cell, you can buy one of those electronic loads at uncle Ali?

https://www.aliexpress.com/item/32821877...web201603_
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#3
@Ivo Staelens: When replying, you don't "have" to include the entire post. Makes for a very long thread when it's just duplicates. Removing the excess quote data. If you are replying to something specific, please only include that part you are replying to.
Just to note, I had just read this thread. Went back to home page and saw there was unread thread. So I came back and it looked the same. I didn't see your reply at first and thought something was goofin up.
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Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

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#4
(02-25-2020, 06:11 PM)Ivo Staelens Wrote:
(02-25-2020, 05:57 PM)100kwh-hunter Wrote: Hi ya all.
This project started several weeks ago and i have good hoops for a good ending, if no good ending: bad luck, waste of money but a LOT of fun.
A forum member brought this to our attention, and i decided to experiment further with it:
Will paste a link.

I think this is the way to build a proper testing cell for some chemistries, in my case the znbr2 cell, before i take it further for a ess: lets build and test.
Test results will be in a separate thread.
.....

Dinner is waiting, i will finish this post tomorrow...also links and grammatically wise, ect
Best

Talking about a detailed building instruction Smile so cool! I will follow with great interest. The scientific papers on this seem to be promising!
Perhaps to measure capacity of a battery cell, you can buy one of those electronic loads at uncle Ali?

https://www.aliexpress.com/item/32821877...web201603_

If you do have success building the cell and measuring some useful voltage, I'd be happy to donate one of my custom battery cycle testers to the cause to measure capacity and cycle life Smile info here: http://rev0.net/index.php?title=CCR#List_of_Features
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#5
I updated my first post.
If there is any question, comment, idea or thought on this particular subject, please share.

@rev0.
That is very kind, i appreciate this very much, especially for the cycle testing.
I would like you to keep a eye on my test results and decide for yourself when you find the testing data sufficient and satisfactory enough.
If you decide to go forward with this i would like to pay for shipping.
Many thanks in advance Rev0.
https://secondlifestorage.com/showthread.php?tid=8776
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#6
Nice work & interesting read :-)
100kwh-hunter likes this post
Running off solar, DIY & electronics fan :-)
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#7
Thanks,
I had a little surprise this morning aldo the cell was not fully charged, i put it on the zb.
It charges with 3.30v and 0.070mah, discharge was from 1.82v to 0.5v and it gave me 0.186mah. Discharge rate was 0.074a.
After discharge it jumped immediately back up to 1.71v
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#8
So the first couples of test run with the blade cells are a no go, they don't work like intended and are very sensitive to pressure.
When they reach proper charging voltage and are taking some power they fail due to pressure, squirt all electrolyte out and contact problems with the electrodes.
Here is my new design, as always: thoughts ideas comments are very welcome.

I bought today some water pipe made from hdpe, dirty cheap 2 diameters both one meter = 15 euro.
Make sure it is hdpe and NOT ldpe or zpe
The diameter i bought where 50 mm and 63 mm, cous they fit into each other.
You can buy this type on 1600 meter! spools, ranging from 16 mm to 80 cm!
How big you want to make your cells, if znbr will work ofcourse.

This is what i bought for cell version 2.0 Cool


I cut up the pieces to length to play with it, clean wash dry ect....
Melt your carbon foils together with your graphite foil.
Melt them onto your pipe for positive.


Now the negative electrode is going a bit more tricky.
The graphite foil must not be larger then the ID! of the small pipe:



Last picture from the bottom side, i let it become too hot, 2 seconds to long, my mistake, but it must be liquid tight! no electrolyte must enter/spoil!

Those two: are your "cup" aka positive side is 63 mm pipe
Your negative electrode is 50 mm!
They fit very nice together.
It should look like this now:


Because this has a lot of testing involved i build 4 different ones.
2 in the length of 5 cm, one in 10cm and one in 15 cm:
Bromine is very expensive in this stage, i bought in a small batch
One 5 cm has 20 cc and phenolic foam in it and the other 5 cm length has no foam in it and holds 50cc electrolide, we will come back later on this.
They look like this:



They are charging now, with a "free floating" negative electrode on top.
just to see IF the chemicals do there work.
I set the chargers at 2.50v to be save, they only go to 1.50v and nothing more after 3 hours.
I set the voltige to 3.30v to get some amps running:
The one without the foam is doing very good, the one with foam...i think the electrolyte must sink in further, probably in the future there will be no more foam, or like Ivo suggested: a layer on the top and a layer on the bottom, test will reveal the best.


For safty reasons and good hope for the future endeavors i created a "solid" negative electrode.
I cut two pipes of different diameters at the same length, melted them together.
To obtain a very simple to make negative electrode with a venting/filling hole, that will be adapted.
Just put your iron on top of it with baking paper in between and let the heat do the rest:

Melt your electrode to it.

Make a cut in the bottom:

Warm up (after cooling them to room temperature) both pieces at the same time on the surface of your iron, 5 seconds or something......
and put them on top of each other:




Long read, i hope this was detailed enough, if not don't hesitate to ask
As always: thoughts, ideas, comments and ect are very welcome.
Thanks for reading and thanks in advance, best: Igor
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#9
(02-29-2020, 05:58 PM)100kwh-hunter Wrote: They are charging now, with a "free floating" negative electrode on top.
just to see IF the chemicals do there work.
I set the chargers at 2.50v to be save, they only go to 1.50v and nothing more after 3 hours.
I set the voltige to 3.30v to get some amps running:
The one without the foam is doing very good, the one with foam...i think the electrolyte must sink in further, probably in the future there will be no more foam, or like Ivo suggested: a layer on the top and a layer on the bottom, test will reveal the best.

Interesting, interesting.


As you can guess, I will share some thoughts on the foam issue.

If I read the scientific papers well, the principle working of the zinc bromide cell is that below a foam electrode is needed. They use carbon foam in order to have it electricaly conductive. The reason they choose foam on the bottom, I think, is that when the cell is charged, The bromine sinks to the bottom and is "caught" by the spongy, foam electrode.

The electrode on top needs to contact the electrolyte also. During discharge, the zink will grow dendrites from the top electrode to the negative electrode. If the zinc touches the bromine layer, the zink will be dissolved. That is also the reason that amperage is limited. The zinc needs time to get dissolved by the bromine layer, if current is too high, the dendrite can reach the bottom electrode and short circuit (read: self discharge).
I also read that optimum distance between electrodes is 0.4cm, so 4mm.

To summarize:

I think a foam below the cell is needed, BUT, it needs to be conductive so that the foam itself functions as an electrode. At the moment I think having read you are using oasis foam (that green stuff to put flowers in). I fear that the oasis has two big disadvantages: it's not absorbing the electrolyte fast enough (and you experienced this already, reading your reports) AND I don't know if the foam is conductive.

I think that results will get better if you replace the oasis with carbon foam. I know when I was searching for a refractory material for my DIY pellet burner I'm building, I found out that carbon foam can be made from ... bread. If you use the technique of charcoal making on the bread (ie put the bread in a paint jar, close the paint jar and put all of this in a fire) That way you will burn off all moisture and non wanted stuff and because no fresh oxygen can enter, you end up with carbon foam. Beware, I never tried it myself but it seems legit.

These are my thoughts, also a long read but maybe interesting...
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#10
Thanks for sharing your interesting thoughts.
The foam must be replaced indeed, but with a more open cell structure.
Even the carbonated bread or such wont do the trick, it stalls the flow.
The liquid must travel freely between the + and -.
Therefore i think a foam of any kind, is indeed the culprit aera and in need of a open cell structure.
If i look at the single experiment from yesterday to this morning, the cell with the foam wanted to have 4.00v to get any power stored.
Cell two (with foam) will take 0.03ah at 4 volts, cell one (without foam) is taking 0.15a at 3.5v.
The discharge (cell one) was to 0.5v at 0.138mah, total was 0.170a, when i put the cell back to charge again it want to have 0.30ah.

(me thinking out loud)
Wouldn't it be better if there is a open (cell)membrane in the middle? so the zinc crystals can develop in full before they hit the bromine and start to self discharge/short circuit?
So the electrolyte can move free and during charge the zinc can not reach the bromine easy?
What also could be an option: create two chambers.
The chamber below only filled with bromine, chamber above filled with a zinc solution.
Hmmm its starting to smell like a flow battery...

I think the optimum distance between the electrodes is a lot more than 4 mm(in this type of setup), the zinc crystals are growing down towards the bromine.
When i checked the cell this morning, i took a peek and there was a nice piek of crystals of about 1.5cm long growing down, and 1-2 mm layer of crystals on the rest of the electrode.
Now that piek is something we don't want, what i would like to see is a 5mm thick layer evenly spread on the electrode.
What if we have a cube of 30x30x30 cm, and we would grow one piek of crystals of 1.5 cm in dia and 15 cm long, wouldn't that be a wasted of all the remaining chemicals?
What if we are able to let it form a layer evenly thick ~3cm on the whole electrode, so we make full use of every particle in the solution?
I have the feeling we just started and it will take a long way and a lot of experiments to get the optimum out of it....if there is a optimum.
I think this is the reason Rob started with the foam.

Thanks for reading, any thought is appreciated.

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