pressurised battery (a mad mans idea)

[jimmyhackers]

ive been doing some thinking lately about the weakest part of all electric vehicles "the battery"

and i think i have an inkling into where current battery techs are going wrong.

its a culmination of the anime "steamboy" my own experimentations with HHO and general observations of current batteries thats made me think so.

and the main question i ask is "why do we vent batteries?" "do we need to vent batteries?"

in essense......my HHO welder..... ater its power supply is turned off, the cells themselves still output a small amount of voltage. like a battery.
but what is interesting is they will output more voltage if i make sure the cells are under a greater pressure.

my hho cells are rated to about 10psi (i go to about 3psi) and costing around £200 each im not about to try and turn them into batteries and pop one and so ends my experimentation.....for now


but i wonder.... if i did have a cell capable of holding immense pressures would the voltage continue to rise with pressure. if so the only limit to the batteries capacity would be the strength of pressure the cell could hold.

very mad i know but let me know what you think about it all.

 

[Syonyk]

and i think i have an inkling into where current battery techs are going wrong.

m'kay... I'd argue they're going very right, with increasing power density and ever safer chemistries with longer life.

its a culmination of the anime "steamboy" my own experimentations with HHO and general observations of current batteries thats made me think so.

and the main question i ask is "why do we vent batteries?" "do we need to vent batteries?"

"So they don't explode like a pipe bomb if they generate gas." Lead acid and nickel iron both generate gas when charging once full. Lithium batteries shouldn't generate gas while charging or operating, but can do so in failure conditions, and the amount of gas generated by the contents of an 18650 cell is more than enough to cause it to explode if not vented. A fully sealed cylindrical cell is more or less a pipe bomb if it starts to generate gas. Pouch type cells won't hold enough pressure before the seams fail to be particularly dangerous (other than the issue that gas generation is typically caused by thermal runaway).

in essense......my HHO welder..... ater its power supply is turned off, the cells themselves still output a small amount of voltage. like a battery.
but what is interesting is they will output more voltage if i make sure the cells are under a greater pressure.

Yes... I believe it's acting as a fuel cell in that mode of operation. Putting more reactants in should lead to higher output.

but i wonder.... if i did have a cell capable of holding immense pressures would the voltage continue to rise with pressure. if so the only limit to the batteries capacity would be the strength of pressure the cell could hold.

Are you referring to a fuel cell type system, or a lithium battery? For a fuel cell, yes, upping the pressure in the storage tanks will increase the amount of reactants you can carry, and increase the power output. However, if you're limiting the gas capacity to the cell itsself, the overall energy stored will be very low.

If I'm not mistaken, the HHO cells produce a combination of gaseous hydrogen and gaseous oxygen (which is then recombined for welding). Storing large quantities of a stoichiometric ratio of hydrogen and oxygen under pressure has the potential to be a lot more excitement and explosion than I care for.

very mad i know but let me know what you think about it all.

I think you've re-invented the hydrogen/oxygen fuel cell.

 

[jimmyhackers]

thanks for the input

im not sure where i was going with all battery techs need to be not vented thing......
but from where i saw it was if you can pump more (elec) into a battery and it vents (lead acid) or goes pop (lithium)

then wouldnt it stand to try and make improvements to the battery containment technology so it doesnt vent or pop. then see how far you could take/abuse current battery technology inside a pressureised vessil which should prevent poping/venting.

along the lines of thermodynamics that what you put in it possibly/potentially will be what you can get out (but genrally less)

i was talking this over with my friend this evening. he did chemical engineering at uni (he also did a stint on hydrogen fuel cells there)
essentiallly what i could create might be a very dangerous thing.....but any superdense battery will be dangerous.

lipos right now if peirced can be a fire bomb. releasing all their energy at once.
now imagine if they had ten times the energy density and went pop. ten times the size fire bomb

were are going to have to admit that.....if we want a 100kwh battery packed into the space of a current 10kwh battery. its going to be dangerous.

and therein is where me and my friend fell a bit short on calculating the feasability of things......basically i got him to find out how many molecules of water there are in 1g or 1ml of water. it was in the order or billions.....anyways.... we then found out how much energy it would take to turn a single water molecule into its component atoms. and then he lost interest and started smoking wacky backy.

my goal was to see the theoretical watts/power required to turn one molecule of water completely into hydrogen and oxygen. and see then how much possible/potential energy storage 1g or one ml of water has.

as soon as i have that number......i can see what tree im barking up

please someone help if you are smarter than me

 

[Syonyk]

im not sure where i was going with all battery techs need to be not vented thing......
but from where i saw it was if you can pump more (elec) into a battery and it vents (lead acid) or goes pop (lithium)

If you pump more electricity into a lead acid battery beyond fully charged, it (somewhat inefficiently) converts the water in the electrolyte (the battery acid) into hydrogen and oxygen. In a sealed battery with recombiners, these are converted back to water in the caps, or in a flooded battery, it's generally vented (hence the importance of room ventilation for battery banks), and you have to add distilled water to the battery to make up for the losses.

Lithium batteries generally react to overcharging by some blend of lithium plating (which can cause short circuits) and overheating, which can eventually cause thermal runaway. http://www.mpoweruk.com/lithium_failures.htm has a lot more detail on the behavior, if you're interested.

then wouldnt it stand to try and make improvements to the battery containment technology so it doesnt vent or pop. then see how far you could take/abuse current battery technology inside a pressureised vessil which should prevent poping/venting.

Your assumption seems to be that the venting/gas generation is a reversible process, which is not the case for lead acid or lithium batteries. It's true for a fuel cell, which you seem to be basing your idea off, but is not generally true for a standard battery.

For the case of lead acid batteries, if you seal them tightly, the cell will build up a highly explosive hydrogen/oxygen mix above the electrolyte level, but combining this back together will only create heat and water, not anything useful for extracting more current out of the battery.

For lithium cells, they generally destroy themselves via thermal runaway, and containing the gasses is not going to allow the cell to be reversed into a functioning state.

i was talking this over with my friend this evening. he did chemical engineering at uni (he also did a stint on hydrogen fuel cells there)
essentiallly what i could create might be a very dangerous thing.....but any superdense battery will be dangerous.

You seem to be insistent that creating a bomb will somehow make for a better battery. Highly compressed hydrogen and oxygen in a confined space is a very efficient pipe bomb. Fuel cells at least generally only store the hydrogen, so you don't have a pressurized container full of both fuel and oxidizer.

lipos right now if peirced can be a fire bomb. releasing all their energy at once.
now imagine if they had ten times the energy density and went pop. ten times the size fire bomb

A lipo, if pierced, will release it's energy over many order of magnitude longer than the time it would take for a container full of hydrogen and oxygen to recombine once triggered.

were are going to have to admit that.....if we want a 100kwh battery packed into the space of a current 10kwh battery. its going to be dangerous.

Yes. And high pressure hydrogen/oxygen is not the way to do this. It's certainly dangerous, but it's no route to 10x battery energy or power density.

and therein is where me and my friend fell a bit short on calculating the feasability of things......basically i got him to find out how many molecules of water there are in 1g or 1ml of water. it was in the order or billions.....anyways.... we then found out how much energy it would take to turn a single water molecule into its component atoms. and then he lost interest and started smoking wacky backy.

my goal was to see the theoretical watts/power required to turn one molecule of water completely into hydrogen and oxygen. and see then how much possible/potential energy storage 1g or one ml of water has.

as soon as i have that number......i can see what tree im barking up

please someone help if you are smarter than me

Your friend is a chemical engineer and couldn't calculate some basic values for number of molecules of a substance in a given mass/volume, the energy needed to separate them, and then the energy released when recombining them? Not a very good chemical engineer... he should be able to do that even quite stoned.

I have a very limited background in chemistry so I'm not going to spend the time to do that, but you're proposing a particularly dangerous form of fuel cell. Hydrogen/oxygen fuel cells are a well known, well studied device, and you should be able to get the numbers that way.

 

[Syonyk]

So, no, you don't have an actual technical argument about my points, you just don't like me because I think lipos are hazardous.

I see.

 

[spinningmagnets]

Whether we are talking about 18650 cells (where the anode is a metal shell around the entire coiled battery guts), or "soft-sided foil packs (of various chemistries)...whenever a condition arises where tiny gas bubbles are forming in the electrolyte, there is less actual connection between the electrolyte and the cathode/anode. since the bubbles are a result of heat, it is crucially relevant that the remaining electrolyte is providing current through a smaller connection between the electrolyte/anode/cathode. This creates an escalating spiral of heat, because the heat of the current (which is obviously reached a point where bubbles are forming) will begin producing even more heat.

Compressing flat foil packs reduces the internal resistance, and moves the curve on the graph down some. Same current will create less heat.

Although putting 18650 cells in a pressure chamber is impractical on an E-bike, its an interesting thought experiment. The resistance of the hot electrolyte to forming gasses would very likely be slowed if it was under pressure (this may be dependent on the exact chemistry). However, I believe that with enough heat in the cell, eventually gasses would start forming, and for every PSI that the gas develops over the pressure chamber...it will expand, bulging the metal shell of the 18650. Perhaps until the positive end pops off to relieve the pressure.

you could say that: The factory vent is not there to relieve pressure (the pressure will get relieved whether you install a vent or not). It is there to ensure where the pressure will relive, and also so that all of the cells will vent their over-pressure in a consistent manner (when an over-pressure condition develops).

Without a factory vent, some cells would pop at a lower internal pressure than others, and some would pop in a violent and dangerous manner. I believe a pressure chamber would slow the effect, since the forming gas bubbles would be slower to form, and smaller during each rise in the heat level. However, when you heat electrolyte, I am certain gas bubbles would still form. I could be wrong, just a thought...

 

[Punx0r]

My understanding is that breakdown of the electrolyte with voltage is purely electrolytic. Increasing the voltage of the cell does increase the energy stored, but I'm sure you'd soon hit some other limiting chemical reaction for that particular cell chemistry.

Syonyk's comments and observations seem spot-on. Nutspecial's personal dislike of him is preventing him from objectively assessing the discussion.

 

[Syonyk]

Although putting 18650 cells in a pressure chamber is impractical on an E-bike, its an interesting thought experiment. The resistance of the hot electrolyte to forming gasses would very likely be slowed if it was under pressure (this may be dependent on the exact chemistry). However, I believe that with enough heat in the cell, eventually gasses would start forming, and for every PSI that the gas develops over the pressure chamber...it will expand, bulging the metal shell of the 18650. Perhaps until the positive end pops off to relieve the pressure.

Do the bubbles form under normal operation within the rated cell limits, or is this something that only happens when you start pushing a cell very hard? I've not been able to find much public research on this issue.

//EDIT: Also, this seems to affect the power output of the cell, not the full energy storage. I would expect the issue to be somewhat less pronounced with a hard cased 18650 or prismatic cell than a soft pouch pack.

 

[spinningmagnets]

I haven't found much research on it. Most professionally designed EV batteries try very hard to keep the C-rate and cell-heat as low as possible. If small bubbles are forming, you have already gone WAY past when the good design parameters have been exceeded.

Prius and Tesla batteries have been lasting many years past their warranty. Their BMS-brains don't take the max possible charge, and has an LVC that is fairly modest, plus the max amps drawn are kept low. The Tesla battery pack is liquid-cooled, even though their max C-rate should only allow the pack to get barely warm under hard acceleration. Millions of dollars of research and longevity testing, and all of it largely ignored by DIY E-bikers.

Fun chat, but...if pressurising a battery pack delays the onset of the downward spiral of heat causing bubbles that increases the heat generated....then it is a bulky and expensive method to fix an already bad design. Use the pressurized chamber money to make the pack larger, and select higher C-rate cells. That way the pack runs cooler. Charge to 4.1V per cell, instead of 4.15-4.20...set LVC at 3.3V per cell, instead of 3.0V...and you can squeeze an extra year out of an expensive pack.

 

[dnmun]

too much misinformation created on this thread by a newbie with no knowledge or experience in battery chemistry.

 

[spinningmagnets]

Several posts from Syonyk and nutspecial have been sequestered to the moderator section for review.

 

[jimmyhackers]

looks like ive restarted an old flame here :S calm down chaps i want answers not a fisty fight

yes technically i am a newbie.

but a fresh point of view on an old subject is required from time to time.

over on my old 306gti6 forum i posted a thread about a steam turbo alternator ran off of exhaust heat. how the whole forum laughed and poked fun at me stating thermodynamics nd all other why it wont work statements... then a few years later a german company had "robbed/borrowed" my design and marketed and made it for truck converstions posting very good mpg efficiencies etc...

sooo its possible some albert einstein is watching and will hopefully rob my idea and then the whole world has better batteries.

and batteries definately need a breakthrough... lipos are good but like i posted earlier about ten time energy density.....
thats the level a battery needs to be to be comparable to a petrol cars range etc....
so we should find a way to aim for it

compressed air powered cars are here and working rather welll......and safely. not sure what exact pressure they run on but i know its around the same psi as scooba tanks which is pretty damn high.

so we can safely hold some pretty raving pressures.....i wonder if i had a hho cell that i could take thousands of psi what results id get.

 

[Syonyk]

compressed air powered cars are here and working rather welll......and safely. not sure what exact pressure they run on but i know its around the same psi as scooba tanks which is pretty damn high.

so we can safely hold some pretty raving pressures.....i wonder if i had a hho cell that i could take thousands of psi what results id get.

Compressed air is not a violent explosion waiting to happen. Compressed HHO (free hydrogen and free oxygen) is, and the activation energy required to do so is disturbingly low. And it's literally just a hydrogen/oxygen fuel cell, so you should be able to calculate the numbers - search for a Bacon Fuel Cell as the easiest form of this to work with.

I'm fairly confident that the energy storage and weight of compressed gas vs solid anode/cathode and a liquid or solid electrolyte come out in favor of the traditional battery construction (or, in the future, the solid state construction, if all goes well).

 

[liveforphysics]

The gases in your HHO cell generate current while one plate has O2 and one plate has H2 in local proximity available to react.

Every HHO generator is also a fuel cell. No matter what cell pressure or temperature, you won't exceed the potential limit of ~1.23V/cell.

In a lithium battery, no quantity or pressure of H2 or O2 anywhere in your cell cause any beneficial effects, but everywhere gasses/bubble are, the liquid electrolyte that is the path for ions to move from anode to cathode for energy storage is blocked as the ions don't move through bubbles/gas.

Also, the gas they produce is predominately CO2 from the carbonates in the electrolyte decomposing, with a tiny bit of H2 microgassing on the anode if you're charging very fast.


Further, fuel cells are a thermodynamicaly dead-end path.

 

[nutnspecial]

Op, I appreciate your out of the box forward thinking, and applaud such.

[some text sequestered to the moderator section for review]

As far the topic, i am not technically knowledgeable enough to argue one way or the other, but wanted to cheer you on. I would like to mess around with hho, and also think that batteries need to improve in capacity, but while also using less toxic and/or limitted resources. I'll be surprised if they achieve both any time soon, but here's lookin up.

So If you were to strengthen and compress the battery containment, would or wouldn't that result in safer and more durable energy storage/discharge.
Kinda like how a modern gun perfectly controls the gunpowder energy for optimal function/discharge. Batteries are just slightly more complex manipulation of nature.

Edit/// \/ Sorry syon. I don't want you to feel like I've personally attacked you. I don't want you to be upset. Sorry again.

 

[Punx0r]

I'm afraid "positive thinking" doesn't trump physics and chemistry. Your interpretation of the information presented in this thread is bemusing.

 

[Syonyk]

[some text sequestered to the moderator section for review]

Do you understand that a HHO cell outputs a stream of oxygen and hydrogen, and that with oxygen and hydrogen available in the cell, it functions as a fuel cell? This is nothing radical. The behavior of hydrogen/oxygen fuel cells is well understood, and the energy density on them is quite terrible compared to batteries. Even pressurizing it doesn't change this.

As for lead acid and lithium, adding pressure doesn't let you pack more energy into them. Overcharging lead acid just creates hydrogen and oxygen very inefficiently, and overcharging lithium cells unleashes a hellish cocktail of gasses, none of which are going to be useful to keep around. You can't just pressurize them and then overcharge them unless your goal is a bomb.

So If you were to strengthen and compress the battery containment, would or wouldn't that result in safer and more durable energy storage/discharge.

It would add weight. That's about all it would do. If your goal is to reduce the energy and power density of a given pack, adding dead weight is a great way to do it, but it's not a path forward for increasing battery capacity or power.

Kinda like how a modern gun perfectly controls the gunpowder energy for optimal function/discharge. Batteries are just slightly more complex manipulation of nature.

And shooting a .22LR cartridge out of a gun built like a cannon isn't going to give you any more energy than shooting the cartridge out of a standard rifle. Once the containment is sufficient to handle the pressures involved, adding stronger containment simply adds weight.

The casing of an 18650 cell is about as light as it can be and maintain strength in the designed-for conditions. Making it heavier accomplishes making it heavier, and it might improve performance slightly in an "abused battery" condition when the electrolyte is already starting to gas, but you're well beyond the cell capacity there, and you'd be better off using the weight to add more cells instead.

Battery R&D spending is huge right now. There are a lot of very well equipped companies filled with very smart people spending a lot of money on building better batteries, and the end result is usually around a 5%/yr improvement. If pressurizing cells was worth the added weight, I assure you, someone would be doing it. And I'm not aware of anyone who is deliberately pressurizing cells.

 

[liveforphysics]

The reason a fuel cell operates under pressure is because it has to for even achieving the meager power density they have.


If you contain/pressurize the gasses a lithium cell produces, you simply lose cell performance as the gases displace area electrolyte once wetted making it useful.

 

[h0tr0d]

If you contain/pressurize the gasses a lithium cell produces, you simply lose cell performance as the gases displace area electrolyte once wetted making it useful.

Questions:
If we pressurize the cell, doesn't it become more difficult for gases to form inside the battery?
Also, if suficient pressure is aplied, don't the gases turn back to liquid?

 

[Syonyk]

If you contain/pressurize the gasses a lithium cell produces, you simply lose cell performance as the gases displace area electrolyte once wetted making it useful.

Questions:
If we pressurize the cell, doesn't it become more difficult for gases to form inside the battery?
Also, if suficient pressure is aplied, don't the gases turn back to liquid?

It depends on the gasses. If it's just hot electrolyte as the gasses, yes, that applies, but in general, that shouldn't be happening unless the cell is badly overloaded, and at that point a lot of other bad things are happening, chemically.

If they're decomposition products from the electrolyte breaking down, then, no, they won't go back into electrolyte.

Based on page 15 of http://www.prba.org/wp-content/uploads/Exponent_Report_for_NFPA_-_20111.pdf, about 11% of the gas generated by a punctured cell is electrolyte solvent, which could probably be condensed back down into electrolyte. The rest, not so much.

Now, that's a punctured cell, but it gives you an idea of the type of gasses you can expect from a cell breakdown.

 

[liveforphysics]

If you contain/pressurize the gasses a lithium cell produces, you simply lose cell performance as the gases displace area electrolyte once wetted making it useful.

Questions:
If we pressurize the cell, doesn't it become more difficult for gases to form inside the battery?
Also, if suficient pressure is aplied, don't the gases turn back to liquid?

Once you've broken the carbonates in the electrolyte into CO2, there is no amount of heat or pressure that will make it form back into a useful carbonate. If you applied enough temp/pressure to liquefy the CO2, you would just be adding useless non-active liquids inside the cell rather than useless non-active gasses inside the cell.

Even if you tried to embrace turning your battery into a fuel cell, and actually plumbed it to flow H2 and O2 over the respective surfaces to make a fuel cell, it would still be impossible to draw energy from that fuel cell until cell voltage dropped below ~1.23V/cell. Which would already be dead empty and damaging for a lead acid cell or lithium cell.

 

[amberwolf]

If we pressurize the cell, doesn't it become more difficult for gases to form inside the battery?

If they were only being formed by evaporation/gasification of a liquid, then probably. But if they are being formed by a chemical reaction/breakdown of a chemical compound, not necessarily.

Also, if suficient pressure is aplied, don't the gases turn back to liquid?

Not necessarily back to the *same* liquid they were before--if they were just evaporation of the original liquid, then probably, but if they are different chemical compounds than the original liquid, then they will not simply recombine, depending on what they were made of and how the original liquid was created, and what caused it to split inot the separate compounds the gases are made from.

 

[Syonyk]

That stuff is fun to play with and holds potential for a variety of combustion based improvements.

None of which is relevant to the topic of battery performance or capacity.

We generally use batteries instead of fuel cells for a long list of very good reasons.

 

[Punx0r]

Thought experiment: Thermally decompose a stick from a tree, collect the combustion gases, compress them under infinite pressure. Will they turn back into the same stick?

 

[Syonyk]

Sorry, NSS? Unfamiliar with that acronym in this context.

This is a thread about an idea for a pressurized battery, in the Battery Technology forum. I don't see how HHO's supposed improvements in combustion performance are particularly relevant.