Read more.Quote:
But currently only delivers half the voltage by volume.
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Read more.Quote:
But currently only delivers half the voltage by volume.
Well the voltage doesn't really matter, just connect two in series, as is done with Lithium polymer batteries. However the energy density may be more serious issue. But then if it can accept high charge rates, that may mitigate it to some extent. But isn't just energy density, physical size is also important.
Well, cheapness might be useful here. Enough of these in series could make a cheap way to add a battery to PCs in case of dodgy power supply - even if it only lasted ten minutes. Home energy storage systems (capturing solar energy from the roof to power the house at night) could be made cheaply, even if the unit was large (as things like this can be hidden in many places in a house). And you wouldn't need to worry about it going really burny either. And 7500 charges is a good 20 years lifespan (charge during day, drain during night). The fast charge isn't so useful here apart from allowing you to top up quickly from the grid if necessary.
This sounds like a good development - as to the density issue, presumably this is "Al/C cell mark 1" so - as the article says - there's plenty of scope for the usual development/refinement.
I'm guessing that in addition to being more damage resistant, the new batteries are also not going to burst into flames, like LiPo are supposed to.
Some cells are easier to set off than others, but overall if it can't burst into flames, then it isn't storing energy :)Quote:
Originally Posted by crossy
Yes, I kind of mis-spoke there - what I was meaning those tales of a battery being dropped or nicked and turning into an incendiary device.Quote:
Originally Posted by DanceswithUnix
True to an extent, but the things that make lithium based batteries relatively dangerous is the metallic lithium formed during the chemical process (lithium is an alkali metal like sodium and potassium) and the electrolyte which I think is dissolved in acetone, which is flammable.Quote:
Originally Posted by DanceswithUnix
That said, LiPo batteries are perfectly safe if handled properly, and you don't forget that they are dangerous! :)
Hmmm.Quote:
Originally Posted by DanceswithUnix
Lithium-ion and lithium polymer (LiPo) represent a very different category of risk to lead acid, NiCad or NiMH, for the simple reason that the latter contain water-based electrolytes, which are inherently non-flammable, but lithium-based secondary batteries use hydrocarbon-based electrolytes, whichcare HIGHLY flammable. Water-based electrolytes have their own hazards, of course, one of which is they can be exremely corrosive, but you have to go some to get them to burst into flames.
Lithium-based secondaries, however, are quite capable of byrsting very violently into flame, bordering on explosion, with very little apparent outside help. There is, however, generally outside help, though it can take several forms.
Essentially, for anyone interested, li-ion and li-po batteries can severely overheat, and if they do, fire can easily result. But why do they overheat? Usually, it'll be :-
- overcharging, or
- chemical thermal runaway, or
- mechanical interference, or
- faulty manufacture.
Any internal short-circuit between anode and cathode can cause cell temp to rise dramatically. And, the electrolyte, be it acetone-based or some other hydrocarbon, is very flammable, so a poor mix with high temps. The temperature inside any given cell is a m7x of outside, ambuent temperature, and inside cell temps. Inside cell temps can be excessive due to charging at too high a rate, or for too long, or to physical punctures if, for example, a battery is dropped, or due to chemical processes causing short-circuits. I have a number of lipo batteries designed to be capable of releasing quire a lot of energy in a short tjme (say, 5 or 6 minutes, from fully charged to maximum advisabke levelmof discharge), and if you do, the can be quite warm. So ..... wait for them to cool before charging.
I certainly wouldn't rule out being able to get NiMH, for example, to burn, but for lithium-based secondaries, accident, abuse or neglect can turn that inherently flammable electrlyte into one hell of a show, when one lets go.
Jyst to reassure users, though, most commonly used consumer batter types are lithium-ion, which nearly always come in a hard plastic shell. The above is one of the reasons why they do. They also contain protection circuitry which, together with proper chargers, means they can't easily be overcharged, at least, if you use the correct charger. In other words, provided they're properly made, they're pretty safe .... which might make people think twice about some really cheap batteries sourced on the internet from places where, well, production srandards may be .... ummmm .... lacking.
LiPo batteries, on the other hand, are less well-protected, often being in foil 'pouches' and much more susceptible to physical damage, that may not be easily or obviously visible. And that's where Peter's comment about 'if handled properly, and you remember they can be dangerous' REALLY comes into play, bigtime. Most people here will probably never user lipo, or at least, that variation of lipo, but he and I both do. I have at least a couple of dozen of them, and use them most days.
Oh, and lithium primaries (non-rechargeable) are also pretty flammable, but for a totally different reason - they contain lithium metal, which itself is highly flammable. Lithium secondaries don't contain free lithium metal, or not beyond microscopically tiny amounts. It's the electrolyte that's flammable in them, which it isn't in Nicad, etc.
Not actually seen one burn but my word NiMH can get pretty exciting if you short them out.Quote:
Originally Posted by Saracen
Have seen someone just get away with dropping a charged NiCd cell pack into their trouser pocket where it shorted on their house keys and I think he was lucky to only wreak his trousers.
Flywheels are the things I find really scary though.
Energy storage isn't trivial.
Absolutely.Quote:
Originally Posted by DanceswithUnix
But changes over the last few years, such as LiPo and LiIon have been quite enabling in some areas, because the energy density, both in terms of physical space, and weight, are actually pretty remarkable. This new technology sounds quite interesting in other aspects, but so far are disappointing in that regard. That said, it's early days yet.
Any stored energy system is potentially dangerous, whether it is stored potential energy (compressed air, large moving mass moving under gravity) endothermic chemical reaction (explosives) or charge (capacitors). The secret is in managing the risks and designing the technolgy for the controlled release of that stored energy.
Those oceans, man...Quote:
Originally Posted by peterb