Sciencemadness Discussion Board - Suggestions for kg quantities of ZnBr2? [for zinc bromide batteries]

Suggestions for kg quantities of ZnBr2? [for zinc bromide batteries]

h2o2guru - 28-12-2008 at 11:45

I ran across a very cool 100+ year old patent for a zinc bromide storage battery, while browsing Google patents. I can't seem to find it at this moment. (I'll post it later)

The crux of the problem is that it uses a "saturated !" solution of zinc bromide , which if my memory is not too corrupted is over 2Kg per liter !!!!

My problem is to turn Kg's of sodium bromide to Kg's zinc bromide.
I'd rather not deal with kg's of elemental bromine (yikes)

The best idea I've come up with is to a salt split with ion exchange resins. (I have many gallons of cation resin sitting in buckets)
unfortunately I'd have to keep concentrations pretty low to keep from "digesting " the resin . many , many liters !

Anyone have any brainstorms of more elegant procedures ???

h2o2guru

[Edit by mod]
Clarifying title in resurrected thread.

[Edited on 16-2-2020 by j_sum1]

kclo4 - 28-12-2008 at 17:44

Sodium Bromide + Zinc Sulfate = Zinc Bromide + Sodium Sulfate

Then, precipitate the Sodium Sulfate.
you probably want to mix the Sodium Bromide with Zinc Sulfate in a saturated solution near boiling. This way upon cooling to near freezing, a significant amount of the Sodium Sulfate will precipitate. look up the solubility graph and figure it out from that though.

Learn some more chemistry, especially what a double displacement reaction is. Wikipedia is your friend

--Also you don't need to use kilograms, you can always use different quantities, just keep the ratio's the same.

grind - 30-12-2008 at 13:20

Dry ZnBr2 should be soluble in ether as ZnCl2 does. That is a possible way to further purification after removing the main part of Na2SO4.

Fleaker - 30-12-2008 at 13:40

What is wrong with consulting Brauer?

There are numerous methods available in that excellent book which are available for free in our forum's library: start at page 1070.

j_sum1 - 15-2-2020 at 22:46

Resurrecting this thread.

I came across this video on DIY zinc bromide batteries.
https://youtu.be/CvSYlMtY1Cg

I have not yet read the relevant papers or the 1902 patent. But it looks like a fascinating project. Not too difficult and very practical. I am not sure about the containment of the bromine when cells are in their charged state. That would strike me as a significant problem in developing an off grid domestic system.

Based on the video, kclo4's suggestion for producing a mix of Na2SO4 and ZnBr2 would seem to be compatible and straightforward.

Anyway, I thought this worth sharing and perhaps having a go at. I will link the papers here when I get a chance to do some reading.

wg48temp9 - 16-2-2020 at 03:18

Quote: Originally posted by j_sum1

Resurrecting this thread.

I came across this video on DIY zinc bromide batteries.
https://youtu.be/CvSYlMtY1Cg

I have not yet read the relevant papers or the 1902 patent. But it looks like a fascinating project. Not too difficult and very practical. I am not sure about the containment of the bromine when cells are in their charged state. That would strike me as a significant problem in developing an off grid domestic system.

Based on the video, kclo4's suggestion for producing a mix of Na2SO4 and ZnBr2 would seem to be compatible and straightforward.

Anyway, I thought this worth sharing and perhaps having a go at. I will link the papers here when I get a chance to do some reading.

I watched the video but he gave no indication (if he did I missed it) of the capacity per kg or per cubic meter or in out efficiency. Yes it would be an interesting experiment if only to give you an idea of how practical or more probably how large the task would be building a battery to power an off the grid house.

j_sum1 - 16-2-2020 at 03:48

Well, you can calculate capacity from the molarity and quantity of solution. And he did quote a current density for charging. I would assume discharge is not dissimilar. And the theoretical voltage can be looked up from reduction potentials. Not that I have done any of this yet. But it is one of the things that appeals: it is very figureoutable.

I was actually considering making it in a charged state. If you already have bromine and zinc, then why not?

Realistically, it will be at least several weeks before I can take on a new project.

Edit: phone type errors

[Edited on 16-2-2020 by j_sum1]

wg48temp9 - 16-2-2020 at 05:01

Having once been a telephone technician I am familiar with the lead acid batterys used in the old electro-mechanical telephone exchanges. Simple construction just lead plates hanging in a square bath of acid. But when I worked out the size required to run my house it would look some thing like this:

Ok I am exaggerating for effect LOL. The pic on the left is about 2kW.h battery and the pic on the right is a typical battery room for a bigish city electro-mechanical telephone exchange. The plates where not plain lead sheets.

clearly_not_atara - 16-2-2020 at 08:02

What a strange thread. Has everyone forgotten how to make hydrobromic acid?

To make ZnBr2, dissolve zinc in aqueous HBr. Distill off the liquids and you have the solid hydrate. I would have thought I didn't need to link a prep of HBr, but anyway:

https://www.sciencemadness.org/whisper/files.php?pid=156645&...

This prep is actually overkill; you don't need azeotropic HBr, as just any HBr will do.

wg48temp9 - 16-2-2020 at 08:46

Quote: Originally posted by clearly_not_atara

What a strange thread. Has everyone forgotten how to make hydrobromic acid?

To make ZnBr2, dissolve zinc in aqueous HBr. Distill off the liquids and you have the solid hydrate. I would have thought I didn't need to link a prep of HBr, but anyway:

https://www.sciencemadness.org/whisper/files.php?pid=156645&...

This prep is actually overkill; you don't need azeotropic HBr, as just any HBr will do.

or as you need some sodium sulphate in the zinc bromide you could you could dissolve zinc in dilute sulphuric acid and sodium bromide then filter off most of the sodium sulphate when its cold.

[Edited on 2/16/2020 by wg48temp9]

SWIM - 16-2-2020 at 09:14

Robert Murray-Smith

I thought he already solved the world energy crisis with his home-made graphene betteries and retired.

clearly_not_atara - 16-2-2020 at 09:31

Quote: Originally posted by wg48temp9

or as you need some sodium sulphate in the zinc bromide

Pardon me, but I wasn't interested in watching a 20-minute video and previous posters in this thread had suggested going as far as using ether to separate ZnBr2 and Na2SO4.

I answered how to make pure zinc bromide, free of impurities. This is not, of course, the best way to produce a mixture, but it is much nicer than laboriously separating Na2SO4 from ZnBr2.

But, re: the OP's concern about working with bromine, it does seem to me that bromine would be produced by this battery while in operation, and that would necessitate having some kind of bromine container one way or the other.

For an at-home DIY battery, the related videos about LiFePO4 seem to result in a less dangerous device.

[Edited on 16-2-2020 by clearly_not_atara]

j_sum1 - 16-2-2020 at 12:32

Sorry for the confusion, CNA. I did a search for previous threads on zinc bromide batteries. My questions are not precisely the same as the OP.

My interest is that it seems a ridiculously simple battery to make with (I think) quite a high capacity. Obviously not without drawbacks (or it would be in commercial use by now). I was interested in whether anyone had any experience with these.

In reality I would think that having tens of litres of Br2 in open containers sitting in your basement is a terrible idea. This is not going to find an application in domestic storage even if the concept is attractive and interesting. But it could still make for a fun project on a smaller scale.