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Creation and building of the of the znbr2 cell
#11
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)
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#12
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 Big Grin 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 pond i 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 Blushsorry

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 charge i will look how 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 out that is going to stop the zinc from growing forward to the bromine.

Thanks
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#13
(03-01-2020, 12:20 PM)100kwh-hunter Wrote: i need something or figuring out that 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 encourage dendrite 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."

[Image: 49606372743_704c24e6a8_c.jpg]
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#14
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 in the 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 that I 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.


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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