Building Big Batteries For DIY Off Grid

[Music] hi so what we've got here is a large battery it's a zinc bromine battery and you can see it's charging at the moment so the bromine's at the bottom here collecting very nicely we've got a clear bit of electrolyte and hiding in here as the zinc now we're going to break this down and show exactly how this should be made the reason i'm doing this video actually is a friend of mine clarence mentor who's giving this a go he's making a whole bank of these things and i thought i would do this as an example so that it would help really to see how i actually built it now it's based on u.s patent 312 802 which clarence sent me because that's what he was going to base his design on so i've based that on that patent if you want to look that patent up now clarence actually has set up a website a web magazine called own power and his idea is to gather that information together and distribute the information out and i'm obviously really in support of that because i'm all about sharing information and if you want to contact clarence to get a copy of his magazine then it is i've got it written here own power as one word at act.zn.com or you can write to him which is clarence.mentor at gmail.com and i'm quite sure he'll free he'd be more than happy to send you a copy of own power they did right to check that i could actually give that information out and he was pretty good with that okay let's break this down as i say this is a zinc bromine battery just missing its electrolyte so what is it well it's got a pretty top on it at least i think it's a pretty top and that top's got a hole in it because we need to stick an electrode through that it's just a circle of plastic with another bit of plastic wrapped around it and that forms a top the key thing actually is this bit here now clarence sent me a patent patent number 312802 which is actually pretty much what this is um built around so it's built around that patent if you get that pen and have a look you'll see pretty much the same thing and it uses a container of a porous clay now i did look for a container of a porous clay couldn't find one thought about making one because as you know i'm a bit of a potter then i thought that's not going to be easy for people to do so then i had to rethink about it so this began its life as a fire brick cut a fire brick in half carved it round into a circle cut out a depth with a hole cutting saw to make the pot and then left some little lips on it so that it rests on the top there and doesn't drop to the bottom so it forms a kind of cup in the center of the battery now that's where the sink is going to go so we'll put the sink in there because it's porous of course the electrolyte will seep through and actually attack the zinc and because it's a luminous silicate it's going to be relatively it well it's going to be inert in that atmosphere as we charge that battery so that's why i made the choices i did and now you'll see that the top actually is kind of a blue color and that's because i've rubberized the top because what's going to happen is that's going to soak up the electrolyte and get wet anything on here is going to come into contact with the electrolyte so i dipped in this material plasti dip plasti dip actually is a plastic coating material normally used for two handles you can dip or paint it i dipped it on until i got a nice rubber coat along the top so the electrolyte can't soak into the lid that i've made it wouldn't really matter that it's plastic but it can't do it the next component we've got here is the positive electrode because the sink becomes a negative electrode remember now we have made this before on previous videos what it is is a bit of aluminium foil encased in some conductive high density polyethylene that's this section here then there's a couple of bits of graphite foil glued onto that it's glued on with heat incidentally and then there's some non-conductive high density polyethylene finally put around there so we made the electrode from scratch and as i say we've done videos on how to make those electrodes if you want to know how to exactly how to make that just review one of those videos now the container itself i actually thought was awesome it is in fact a candle holder from my local supermarket so all you're supposed to do really is drop a tea light in there you get a pretty candle holder so i got this candle holder because it's a nice volume it's one and a half liters it has this little sort of section in here which is kind of cool and a wooden base for it to sit on so the whole battery goes together like that candle holder then our positive electrode which we've made then our pot from the fire brick which we've made and then we put in the zinc and on goes the top and that will be the battery obviously we're going to put electrolyte in there in a minute and later i'll talk about the electrolyte now this pot because it's a pot we'll take lots of different kinds of zinc we could put zinc powder in there we could put zinc granules in there we can use scrap zinc which is what i'm going to use because i've got some grass crab single foil crush it up a little bit poke it in there as long as those zinc pieces are in contact with each other it's going to be a really nice negative electrode so if you're using powder or granules you need to take compact so make make sure that they actually touch each other now this battery the energy is stored in the electrolyte it's not stored on the electrodes so when you think about other batteries things like a lithium ion battery and things like a manganese dioxide battery the energy actually comes from the electrode material itself the active material on the electrode these are very unusual in that they come from the electrolyte and that's makes them sort of really good for flow batteries so it's kind of like a stationary flow battery if you like now zinc bromide batteries are really well known there is a lot of information about zinc bromide batteries so if you want to know more about them just have a read up on them there's just such a lot out there this is a specific build for a well-known chemistry and it's meant to help people build their own devices so what we're going to do really is scrunch up the zinc pop it in there leave a tail out here and fill that with electrolyte okay so what we've got here is one and a half liters of 2.5 molar zinc bromide that's going to go in here now the key to understanding this battery is that realization that the energy isn't stored in the battery plates they don't really matter actually they're just a point at which we can transfer the energy the energy is actually going to be stored in here and the separation of this now 2.5 molar means there's a specific number of atoms molecules floating around in there when we charge you what we do is we transfer two electrons per molecule because it's znbr2 so zinc has plus two two br minuses we've got two electrons per molecule now a mole is a specific number of molecules it sits roughly six times ten to the 23 molecules it's a lot of molecules and we have two and a half times that actually this is in fact 2.5 molar zinc bromide with 0.5 molar sodium bromide to help with conductivity because as we charge this what we're doing is we're pulling out the zinc and depositing it as zinc metal and we're pulling out the bromine and depositing this bromine liquid so um it will go down in conductivity as it charges so as it gets near to the end of its charge the conductivity is going to drop and so it's going to be kind of self-limiting because it can't pass any more charge that is a cool thing if you want that but it can be a bit irritating so half a mole of sodium bromide will help to continue that charge when we're charging we are passing a specific number of electrons two for each molecule of zinc bromide that we separate out so we separate the zinc and deposit it we separate the bromine and deposit and that takes two electrons if we have one mole of electrons then we've got six times 10 to the 23 here obviously we've got 2.5 moles so it's 6 times 10 to 23 times 2.5 or if you like uh 18 times 10 to 23 molecules and that will take two electrons each so we need 36 times 10 to the 23 electrons to make sure that that is totally separated and that's because that's the amount of zinc bromide we've actually physically got here as a big lump and we need that number of electrons now luckily enough coulombs is the number of electrons if we pass 6 times 10 to the 18 coulombs across a wire what we have in fact got is an ampere second an amp power is 3600 coulombs an amp second is one coulomb per second passing a point and a coulomb is a specific number of electrons six times ten to the eighteen so you can work out how many electrons you need and therefore how many amp hours that battery is going to give you from the amount of zinc bromide you've got because that's where all the energy is stored now i understand that's a bit um quite a bit of math actually but it's relatively simple just look up ampere look up coulomb and then you're gonna be there and if you look up avogadro's number you'll know what the moles mean so it's actually pretty simple stuff so when we pass that in there we will separate that out to the amount of coulombs on the amount of amps and we'll reverse that now obviously it's not 100 efficient there's going to be lots of inefficiencies because it's a diffusion process that is everything separates when we turn it off it begins to diffuse across again and diffusion is slow takes energy and is inefficient so you're going to expect roughly an 80 return of that energy something round about there will give you a ballpark figure of what it is that your device is going to store so you can calculate for the volume of material the molarity of the material how much energy you're going to store in the battery you build just by using that information now i mentioned it was a diffusion process and that makes it slow so although a lot of energy is going to be stored in here it can't be released in microseconds that's the job of supercapacitors it is a battery so in those terms it'll be a little slower so it'll be energy dense but the ability to release energy quickly is power density so power density is energy over time so there'll be a lot of energy in here it won't have a high power density it's not going to crackle wires anything like that anytime soon because it's relatively slow so you need to be aware of that now the power density the ability for that reaction to happen is to do the surface area of the electrodes and the diffusion rate across the electrolyte so if you have a small surface area electrode you're going to get still same energy density but the power density will be rubbish if you have a higher surface area electrode you'll get much better power density so the power density of this my bit of zinc that i put in there is going to be quite low if i did powder compact it and put electrodes in it'd be much higher if i did something to affiliate the surface as a bigger surface area we'd be much higher and so on this actually is um really easy to make and there's always a trade-off there because a valiated surface actually can be terribly difficult to make and can be quite expensive so if you want to accept that trade-off of having lower power density but higher but it's reasonable energy density and a lower cost then that's the way to go but it'll be up to you about what it is that you want to do okay i'm going to fill this with the electrolyte now and then we'll get the thing on charge okay that's it ready to go i've filled it with electrolyte connected into the power supply and it's ready to charge now the eagle eyed will have noticed a couple of things about the positive plate one it's not at the bottom remember i talked about that little indentation and quite liking that and how the fact that the plate's not actually at the bottom and two it's full of holes now i've done that because according to the patent the bromine should settle at the bottom and this allows it to do that my experience is a bit of diffusion the bromine will settle to the bottom but there's still a bit of diffusion and the holes allow it to do all of that stuff the um charging regime actually is not like other batteries you don't put it a specific voltage what you do is put put it at a specific current density it needs to be somewhere between 20 and 50 milliamps per square centimeter of electrode surface so if you've got 100 square centimeters you're going to charge this at two amps you need to turn the voltage up so that two amps will pass that's a lot of voltage now if you're doing it too high you will see the water splitting and it'll be bubbling so turn your voltage down and reduce your ampage that's how you charge these things now this thing remember it is a bromine-based battery and bromine is a halogen so if you smell something like a pool then you're getting bromine coming off you build a cell and smell that typical pool smell the bromine actually stays captured you don't want to spill it if you spilled this when it's in its charged state you're essentially spilling bromine everywhere now i'm not a great one for scarce stories obviously i mean you know i think you should give things a go but you also have to do it with a measure of caution sometimes and halogen batteries are those things you need a measure of caution amount so make sure that you read up those caution measures because remember this is an extremely popular battery and there's a lot of information about it and how to deal with it don't just look at this and think yeah i'm going to give that a go do read up about it a little bit particularly on the safety measures of it because it is a halogen battery and particularly charge and discharge characteristics of it i'm just giving you a quick introduction on how to go about this this is by no means in depth of everything about this battery you can make this battery from this video you can charge and discharge this battery from this video but i can't urge you enough to do a bit more reading before you go ahead just to make sure you know what you're doing anyway this is ready to charge so just turn it on now i've got that set at a very low voltage so if i bang up the voltage and i'm going to charge it around a couple of amps or so so i've got nine volts on that and now it's charging you should be able to see there's a kind of a yellowish color forming already on the plate which is the collection of the bromine so here it is charging you should be able to see the bromine forming on that positive plate and sinking to the bottom okay because it's a video i've only been charging it for about five minutes and you should notice quite a few things all the bromine sinking to the bottom this bits nice and clear i've actually got a little motor here that i'm going to attach [Laughter] that has considerable power in it already actually so i just wanted to demonstrate that it is in fact working it'll take a while for that to charge actually now you'll know it's charged because the amperage will drop down a bit and you need to put the voltage up to maintain the amp rate because remember it's charged by current density as we look at this we can see there's no off gassing so it's even though it's going to be chart air it is actually charging at the moment at 7.6 volts we're not splitting the water because it's preferentially plating the zinc and gathering the bromine once it's done that what it's going to do is start splitting the water so you'll be able to see the gas being given off and that gas will be hydrogen gas now it is giving off a tiny amount of hydrogen gas because they all do all these reactions happen at voltage plateaus and they're all in competitions it's a very small amount but it's really tiny but you do need to pay attention to the bromine gas possibility and the hydrogen gas possibility so it's just like a lead acid battery when you charge a sulfuric acid battery it gives off hydrogen gas when you have a lot of sulfuric acid batteries and you're charging those in a big bank of them then you don't do it in an unvented space and you've got the same thing here this can't be charged in a completely sealed area because you're just creating problems just like if you tried to charge a lead acid battery in a completely sealed area one battery doesn't really matter a hundred batteries you're going to have a problem so you don't charge batteries in sealed areas you make sure that you vent them the other thing that we could do with this if the liquid does bother you me it doesn't bother because you know i know all about these things i know how to take care of them so i really don't care but if it did bother you then you could join the liquid with something like fumed silica fumed silica is silicon dioxide it's actually got in this brick as well this is an aluminium oxide silicon dioxide brick if you put a lot of hume silica in there it'll go very gel like once it's very gelatinous of course you're not going to spill it i mean a little bit of liquid spilled makes a big mess when you gel it you won't make that big mess so you could also gel the thing that would certainly help but that is how to make a big battery now the volt discharge voltage is 1.8 volts so you're going to need a few of them to get to 12 volts but if you want to make a big battery there's a really good way of making a huge battery now i thought i'd share that with you and the information about clarence and what he's up to i hope you enjoyed the video i'll go and finish charging this and see what it can do and thank you very much for watching

Channel: Robert Murray-Smith

Views: 86,723

Keywords: battery, zinc, bromine, bromide, diy, off, grid, homestead, robert, fwg, murray-smith, home, made, batteries, chemistry, energy, electricity, storage, d-i-y, technology, project, green, environmental, science, fair, build, how to, make, power

Id: j75_mYwA_E8

Length: 18min 27sec (1107 seconds)

Published: Tue Oct 20 2020