Creation and building of the of the znbr2 cell


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100kwh-hunter

Member
Joined
Mar 2, 2019
Messages
820
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 thisand 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 cellstheoretically could store =~14to 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:

image_ynkbzk.jpg



image_idslfq.jpg


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!


image_avznax.jpg


Iron in total 4 pieces carbon foil with one piece of graphite foil together, onepiece at a time! use your baking paper so you wont DUCK 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:

image_bvizdb.jpg


Press this in your oversized oasis:

image_gqytfe.jpg


image_mrpvjd.jpg


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

Now thethickerpart:

image_myrkwc.jpg

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!!!!

image_cqhirj.jpg

DUCK 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.

image_nozwat.jpg

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

image_htbiod.jpg


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!

image_eoprkz.jpg

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.

image_izwgzh.jpg


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 transcuralendfluid clear as water. dont let the sediment come back into your solution.

After just 12 hours i got this:

image_ginyir.jpg

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

image_yqjyjq.jpg


The sediment is some cheap undissolvable salt, that has nothing to do with the zn or br.
Bromine salt is gainedfrom 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!

image_cncefz.jpg


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

image_eyslem.jpg

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

image_fpecck.jpg

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.

image_byufkp.jpg


Again:When charging, the first or the 10.000st time, positive is always down andnegative always up! This is the influence of gravity on the ZnBrcell
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
 

Ivo Staelens

Member
Joined
Aug 21, 2017
Messages
109
100kwh-hunter said:
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 :)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/328...earchweb0_0,searchweb201602_,searchweb201603_
 

Korishan

Moderator
Joined
Jan 7, 2017
Messages
7,005
@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.
 

rev0

Member
Joined
Oct 3, 2017
Messages
372
Ivo Staelens said:
100kwh-hunter said:
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 :)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/328...earchweb0_0,searchweb201602_,searchweb201603_

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 :) info here: http://rev0.net/index.php?title=CCR#List_of_Features
 

100kwh-hunter

Member
Joined
Mar 2, 2019
Messages
820
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
 

100kwh-hunter

Member
Joined
Mar 2, 2019
Messages
820
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
 

100kwh-hunter

Member
Joined
Mar 2, 2019
Messages
820
So the first couples oftest 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:


image_anqlcv.jpg

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.

image_zlyrhm.jpg


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

image_einnyr.jpg


image_zjaxtw.jpg


image_znpvzq.jpg

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:

image_vlkajp.jpg


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:

image_nqronq.jpg


image_dwudxu.jpg


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 electrolytemust 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.

image_greyrr.jpg


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:

image_ptyzvm.jpg

Melt your electrode to it.

image_qfyjez.jpg

Make a cut in the bottom:

image_vmfabr.jpg

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:

image_chfwwu.jpg




Long read, i hope this was detailed enough, if not don't hesitateto ask
[size=small]As always: thoughts, ideas, comments and ect are very welcome.[/size]
[size=small]Thanks for reading and thanks in advance, best: Igor[/size]
 

Ivo Staelens

Member
Joined
Aug 21, 2017
Messages
109
100kwh-hunter said:
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 electrolytemust 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.

image_greyrr.jpg

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...
 

100kwh-hunter

Member
Joined
Mar 2, 2019
Messages
820
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.



image_jvzkbo.jpg
 

Ivo Staelens

Member
Joined
Aug 21, 2017
Messages
109
Is a activated carbon foam filter part for fish tanks usable? You should have experience with them and have something lying around (as you have a professional looking fish pond)
 

100kwh-hunter

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Joined
Mar 2, 2019
Messages
820
It is made out of pvc with a layer on it
I had a pretty professional pond and filter, 2 x 4 chamber filters each containing 3000 liters of water.
First chamber = brushes to get the worst dirt out, second and third chamber big mash bacteria sheets, fourth chamber fine mash bacteria sheets, pumps 20.000l per filter they pump it into a barrel that has 300um mash into it, saturation of oxygen was 80% with 5 grams salt a liter water...I think this was pretty pro yes :D :cool:
I think you are referring to aquariums filters, they use that indeed. also used in air filters indoors
Indeed as screens or as lose coals, both are activated.
For the type of magnitude for the pondi had, there is only pvc with a coating, it would be getting really expensive, or use zeolite.
If your balance is ok you don't need or even want them, under 1500l it is a must, mine was 180.000 liter (with pipes filters ect 210.00l) crystal clear better than drinking water pond.
Yes very proud owner :blush:sorry

How ever you made me think.
I don't know how it is called in english but you will know what i mean: "worteldoek", it is made from hdpe.
Has an open structure.
For a "mash" filter/barrier? better then ?
After every chargei will lookhow the zinc is developing.
Maybe a longer/higher cell?
Leveling out the floating electrode will also help, they seek the path of the less resistance.
Btw i was able to do two cycles in the meantime....
Cell one without foam 50cc at 1.75 M solution is now taking 350mah and giving 350mah, cycles where approx 1 hour and 15 min.
After discharge the cell came back at 1.77v.
I think i am going to make one for 180cc at 1.75 M
The cell with oasis in it is still doing nothing, at 4.2 v it wants 0.03a, discharge only with a led for not even 5 minutes.
Oasis is out, carbon foam is ordered(or lose (activated) coal), i need something or figuring outthat is going to stop the zinc from growing forward to the bromine.

Thanks
 

vspin

New member
Joined
Aug 12, 2018
Messages
17
100kwh-hunter said:
i need something or figuring outthat is going to stop the zinc from growing forward to the bromine.

Princeton found that a negative current collector with little surface area (smooth) encouraged dendrite formation while a negative current collector with much greater surface area (carbon cloth in their case) did not encouragedendrite formation.


To control hydrogen, consider (IMO):

1. Lower the cell's headspace (may not apply to you).

2. Do not use supporting salts (may not apply to you).

3. Invert the electrodes. I've created the image below of Princeton's inverted architecture. Note that the bromine is congregating above the negative carbon cloth, around the positive carbon foam.

When the hydrogen bubbles up from the bottom to the top, it reacts with the bromine around the positive electrode and "redissolves it back into
solution as HBr(l), thus recapturing any potential losses."

[img=541x765]https://live.staticflickr.com/65535/49606372743_704c24e6a8_c.jpg[/img]
 

100kwh-hunter

Member
Joined
Mar 2, 2019
Messages
820
Thanks for the info vspin,
My negatieve electrode holds ~70% of the surface area of the positive electrode.
Making the neg surface smaller could be the trick, it sound logical, they want to form.
But will the charge/discharge not go slower?
Test is added to the list!

Also i would like that the bromine is as low as possible, aldo it can collect inthe foam more to the top.
Bromine is in my case"sealed" with the water on top, so no vaporization of poisonous gasses.
It is really a very irritating gas, i am very glad i have proper ventilation in the shed.
Sometime if i look to the development of the zinc, some of it breaks of and sinks to the bromine layer.

The headspace/electrode is approx 1 cm deep, i was planning to make the total head length and cell case longer to possible seal it for incoming air and give the hydrogen more room to expand.
The reason is thatI think one cell spilled some under charge, mah is approx 150 to 200 lower, level approx 1 cm lower, bench was "wetish" underneath.
Eventually it will create a small vacuum, with the benefit that there is no escape of the hydrogen possible(self balancing in atmospheric pressure, i hope)
A valve is easy to make, 5 cent coin on a piece of rubber that covers the vent hole

It is also worth to try it out, reverse polarity, and put the positive electrode into a carbon cloth.
Test added to the list!
Could be even a simpler construction design, i will come back on this one.

Before i am going to add any additives i would like first to make a list of possible additive that dont do much harm to the self life of the cell....
Most experiment i found that used additives (supporting salts as well) improved the cells c rate but not the capacity or! the self life!.
I would rather have a cell with low capacity and a low c rate and a lot of them that will last longer then i live.
I would rather not rebuild everything again every 10 years with declining values over the years.

@Ivo,
Test with carbon and activated coal on the bottom where also added to the list, hdpe screen from "worteldoek" was also edit.

As i crawl on my belly in the mud the cell design is improving step by step.
Thanks all.



image_hszzuz.jpg

1 is the zinc built up
2 neg electrote
3 level of liquid
4 1.75 m solution
5 positive Shell
6 neg Shell
7 as 1
 
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