How fast can a large battery be charged and/or recharged?
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How fast can a large battery be charged and/or recharged?
I remember in chemistry class years ago tracing in detail how a battery works. Yet there was little discussion (from what I can recall) as to how fast a battery can be charged and what the limiting factors are.
Now, of course, storge technology is the future and EVs are being "strongly encouraged" (I leave that specifc discussion to the political hamsterwheels). Understandably, the general population is concerned about charging times. We don't mind it for our mobiles and the small batteries we recharge for our remotes and such, but waiting for the auto to be good to go is requiring a few thought and time adjustments.
Why does it take so long to charge a battery? I imagine it as an energy density problem, but it takes just a few minutes to fill my auto with petrol and so why can't I recharge a battery with that equivalent of energy density?
Will this problem ever be resolved or do the physics simply prevent real-time large storage recharges?
Now, of course, storge technology is the future and EVs are being "strongly encouraged" (I leave that specifc discussion to the political hamsterwheels). Understandably, the general population is concerned about charging times. We don't mind it for our mobiles and the small batteries we recharge for our remotes and such, but waiting for the auto to be good to go is requiring a few thought and time adjustments.
Why does it take so long to charge a battery? I imagine it as an energy density problem, but it takes just a few minutes to fill my auto with petrol and so why can't I recharge a battery with that equivalent of energy density?
Will this problem ever be resolved or do the physics simply prevent real-time large storage recharges?
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Heat becomes a significant issue as charging is not a 100% efficient process - the faster you pump in the electricity the hotter it gets and heat is generally not good for battery health. Filling your car with petrol is a physical process so the equivalent for an EV is dropping the batteries out and replacing with a freshly charged set.
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I remember reading about the chargers are designed to deliver the charge in tickles / drops and research is underway to develop the charge in larger doses. However that was for mobile chargers not batteries for electric vehicles.
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Getting energy in and out without disrupting the structure of the battery appears to be one limit, considering that the charge/discharge process in a chemical cell needs physical movement of ions, and the faster you do that, the greater the chances of the internal make-up changing over time to the detriment of the battery. There is also the issue of waste heat and cooling, because of the effective resistance of the unit - too much current and permanent damage will result.
On the positive side, we are nowhere near (as in 20+ orders of magnitude) any kind of fundamental physical limit for energy storage, and as a highly inventive species when we aren’t being distracted, I’m sure things will improve for the foreseeable future.
On the positive side, we are nowhere near (as in 20+ orders of magnitude) any kind of fundamental physical limit for energy storage, and as a highly inventive species when we aren’t being distracted, I’m sure things will improve for the foreseeable future.
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A few years ago when we had in-race refuelling they could put 110 gallons of fuel into an F1 car in under three seconds - why does it take over a minute to full the tank of your Ford Mundano? The answer is (of course) that the Mundano has smaller filling pipes that can't take that kind of flow, and the filler system can't be pressurised.
It's essentially the same thing with the electric vehicle. The "pipes" (the conductors) are engineered to carry the fuel (pressurised electrons) at a certain rate. The bigger that rate the bigger the pipes need to be, and as these pipes are solid metal this makes them heavier so you don't want to have them much bigger than you actually need. This is where the pipes analogy falls down a bit. If you try to push fuel through a pipe faster than it will go you just get back-pressure. But if you push electrons through a conductor at a higher rate the conductor gets hot. This actually dissipates some of the energy you're trying to squirt in (think of it as a fuel leak), but it can also damage the conductor. Not the main "wires & stuff" conductors, but the network of smaller conductors which carry and distribute the flow of electrons down into the plates in the depths of each cell. These plates are fragile things - just a foil a few thou thick. Getting hot can buckle it (which might short it to the next plate) or burn patches of the electrolyte off the plate (effectively reducing the capacity), so the plate's ability to carry the current and dissipate the heat are a fundamental limiting factor.
And of course even when the heat is within acceptable limits it has to go somewhere when it is effectively "lagged" by the surrounding electrolyte and insulation. So heat soaks through the whole battery when being charged or used, and the whole battery heats up. If its temperature gets above a critical value (lithium chemistries) it can kick off a self-fuelling fire. So the whole battery bay would need extra cooling during a faster charge (or discharge), which is more weight, more complexity and more energy lost (another fuel leak). Cooling the INSIDE of a large pack of batteries isn't just a matter of adding fans - it needs active coolers like Peltier Pumps which are expensive and relatively short-lifed items*.
This is turning into the full lecture, so I'll leave it at that taster. The bottom line is that the charging takes as long as it does because of the various limitations in the technology and the ensuing trade-offs against size, weight, cost and reliability. But against that you get the advantage that you can typically refuel at home, so if the top-up takes 90mins and a full charge takes 5 hours this can be done while you're sleeping or watching TOWIE (The Only Way Is EASA) rather than standing in the rain at a petrol station...
PDR
* The "Energy Store" in the current breed of Formula 1 cars has a large pack of lithium-cobalt cells with lots of monitoring sensors/electronics and embedded Peltier cooling. They weigh nearly 30kg, can deliver 160bhp for 30 seconds and can recharge in about 1 minute. But they barely last 6 races and cost over $400,000 each. After 3 races their capacity is typically reduced by 15-20% due to damage from the fast charging
It's essentially the same thing with the electric vehicle. The "pipes" (the conductors) are engineered to carry the fuel (pressurised electrons) at a certain rate. The bigger that rate the bigger the pipes need to be, and as these pipes are solid metal this makes them heavier so you don't want to have them much bigger than you actually need. This is where the pipes analogy falls down a bit. If you try to push fuel through a pipe faster than it will go you just get back-pressure. But if you push electrons through a conductor at a higher rate the conductor gets hot. This actually dissipates some of the energy you're trying to squirt in (think of it as a fuel leak), but it can also damage the conductor. Not the main "wires & stuff" conductors, but the network of smaller conductors which carry and distribute the flow of electrons down into the plates in the depths of each cell. These plates are fragile things - just a foil a few thou thick. Getting hot can buckle it (which might short it to the next plate) or burn patches of the electrolyte off the plate (effectively reducing the capacity), so the plate's ability to carry the current and dissipate the heat are a fundamental limiting factor.
And of course even when the heat is within acceptable limits it has to go somewhere when it is effectively "lagged" by the surrounding electrolyte and insulation. So heat soaks through the whole battery when being charged or used, and the whole battery heats up. If its temperature gets above a critical value (lithium chemistries) it can kick off a self-fuelling fire. So the whole battery bay would need extra cooling during a faster charge (or discharge), which is more weight, more complexity and more energy lost (another fuel leak). Cooling the INSIDE of a large pack of batteries isn't just a matter of adding fans - it needs active coolers like Peltier Pumps which are expensive and relatively short-lifed items*.
This is turning into the full lecture, so I'll leave it at that taster. The bottom line is that the charging takes as long as it does because of the various limitations in the technology and the ensuing trade-offs against size, weight, cost and reliability. But against that you get the advantage that you can typically refuel at home, so if the top-up takes 90mins and a full charge takes 5 hours this can be done while you're sleeping or watching TOWIE (The Only Way Is EASA) rather than standing in the rain at a petrol station...
PDR
* The "Energy Store" in the current breed of Formula 1 cars has a large pack of lithium-cobalt cells with lots of monitoring sensors/electronics and embedded Peltier cooling. They weigh nearly 30kg, can deliver 160bhp for 30 seconds and can recharge in about 1 minute. But they barely last 6 races and cost over $400,000 each. After 3 races their capacity is typically reduced by 15-20% due to damage from the fast charging
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Originally Posted by PDR1
A few years ago when we had in-race refuelling they could put 110 gallons of fuel into an F1 car in under three seconds -
110 gallons seems an awfully large volume of fuel when you consider that current F1 cars only carry about 40 gallons US (or about 32 imperial gallons).
I know that engine efficiency has increased massively but 110 gallons seems a lot.
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Originally Posted by 747 jock
Is that figure correct?
110 gallons seems an awfully large volume of fuel when you consider that current F1 cars only carry about 40 gallons US (or about 32 imperial gallons).
I know that engine efficiency has increased massively but 110 gallons seems a lot.
110 gallons seems an awfully large volume of fuel when you consider that current F1 cars only carry about 40 gallons US (or about 32 imperial gallons).
I know that engine efficiency has increased massively but 110 gallons seems a lot.
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Long time since electical instruction, but I seem to remember that temperature was the primary governing factor - 'Thermal runaway' was not nice - expecially in aircraft! The Beverley was a mainly elecrically operated beast and we had enormous NiFe cells in the battery box to cope with the loads and the 'Hammond Organ', with its BTH units, taking care (or not!) with the distribution. 'Impact technology', with the BTHs and the clamshell doors mechanism was very much the order of the day!
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Supercapacitors can charge up pretty quick, their problem however is when they release their energy, although you get plenty of amperage out of them the voltage drops off too fast to make them practical.
Most battery structures are a series of smaller cells connected in parallel, which themselves are connected in parallel or series, and that hierarchy may repeat itself a few more times to define "the battery". The Tesla battery pack contains 7,104 18650 cell batteries in 16 x 444 mini packs. These days electronic smarts control the rate of charge and discharge almost to the lowest cell level. You can kind of see why such structures are slow to charge.
Wouldn't it be ideal to have a battery that charges up like a supercapacitor and discharges like a normal battery, perhaps using separate anodes/cathodes for the purpose. I'm sure it would have been invented already if it could be done.
Wow, a $400,000 battery that only lasts 3 races. Perhaps using a bottle of liquid nitrogen would be cheaper than Peltier pumps which also generate heat as they cool. Funny business is F1.
Most battery structures are a series of smaller cells connected in parallel, which themselves are connected in parallel or series, and that hierarchy may repeat itself a few more times to define "the battery". The Tesla battery pack contains 7,104 18650 cell batteries in 16 x 444 mini packs. These days electronic smarts control the rate of charge and discharge almost to the lowest cell level. You can kind of see why such structures are slow to charge.
Wouldn't it be ideal to have a battery that charges up like a supercapacitor and discharges like a normal battery, perhaps using separate anodes/cathodes for the purpose. I'm sure it would have been invented already if it could be done.
Wow, a $400,000 battery that only lasts 3 races. Perhaps using a bottle of liquid nitrogen would be cheaper than Peltier pumps which also generate heat as they cool. Funny business is F1.
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Originally Posted by cattletruck
Supercapacitors can charge up pretty quick, their problem however is when they release their energy, although you get plenty of amperage out of them the voltage drops off too fast to make them practical.
Never say never, though; as far as I know the issues are all in the engineering rather than the physics, and it's plausible that a supercapacitor of the future might also be longer-lasting or cheaper to produce than chemical batteries.
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Originally Posted by cattletruck
Supercapacitors can charge up pretty quick, their problem however is when they release their energy, although you get plenty of amperage out of them the voltage drops off too fast to make them practical
In my Texas city, we have a light rail system that for part of its route runs over a bridge and for that part, there is no overhead. Not sure if they use capacitors or an onboard battery though
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Originally Posted by pasta
. . . The fundamental issue (with current technology) is energy density; from memory Tesla are getting in excess of 800Wh/kg, whereas supercapacitors are typically in the order of 10Wh/kg. . .
As far as I know, a charged battery doesn’t weigh any more than a discharged one - the chemical energy stored in it waiting to be converted back to electrical energy does not seem to have mass. Batteries are heavy - is that a coincidence or is there a physical (i.e. physics) reason that they have to have significant mass?
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Originally Posted by 747 jock
Is that figure correct?
110 gallons seems an awfully large volume of fuel when you consider that current F1 cars only carry about 40 gallons US (or about 32 imperial gallons).
I know that engine efficiency has increased massively but 110 gallons seems a lot.
110 gallons seems an awfully large volume of fuel when you consider that current F1 cars only carry about 40 gallons US (or about 32 imperial gallons).
I know that engine efficiency has increased massively but 110 gallons seems a lot.
This keyboard never types what I tell it to. I will tell one of the game keepers to give it a sound horsewhipping until it dispenses with this insolence.
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Originally Posted by cattletruck
Wow, a $400,000 battery that only lasts 3 races. Perhaps using a bottle of liquid nitrogen would be cheaper than Peltier pumps which also generate heat as they cool. Funny business is F1.
If you do the sums on how much liquid nitrogen you'd need to cool the energy store for a whole race (up to 2 hours) you'll see why that weight trade-off isn't taken.
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Originally Posted by pasta
You could probably work around that with some sort of voltage regulator.
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Originally Posted by Ant T
Is there a fundamental reason why all the current methods of storing electrical energy seem to be heavy?
As far as I know, a charged battery doesn’t weigh any more than a discharged one - the chemical energy stored in it waiting to be converted back to electrical energy does not seem to have mass. Batteries are heavy - is that a coincidence or is there a physical (i.e. physics) reason that they have to have significant mass?
As far as I know, a charged battery doesn’t weigh any more than a discharged one - the chemical energy stored in it waiting to be converted back to electrical energy does not seem to have mass. Batteries are heavy - is that a coincidence or is there a physical (i.e. physics) reason that they have to have significant mass?
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Electrons only amble along conductors. They're not very big, and it seems a shame that we can't put a block of electrons into a container to be used later.
That was three statements of no particular worth.
Bereft of empiricism, one had to invent ways of learning. In one of my early jobs there was a huge battery charger for customers that had battery radios. I connected an electrolytic with a working voltage of ~ 25v across a 100v supply. The plastic sheath over the aluminium case started to bubble. I became concerned for my safety and backed out of the tiny workshop. There was an almighty bang, and one could barely see across the room for a snowstorm of electrolyte. One has to be careful with the pressurising of electricity into small places on a reduced timescale.
Just as an aside. In the same workshop, I connected a little glass neon bulb across the mains - without its resistor. My little girly scream was more to do with the fear of being blinded than the very loud crack. I ran out of the room into the arms of my old science master, a man that had seen me blow a lump out of the high Victorian ceiling of the science room, before, during a nightschool lesson, setting the room on fire. He just rolled his eyes. Some things are not going to change.
I didn't get into trouble about the fire. He'd given the nod to me holding a piece of phosphorus over the Bunson flame. Flaming bits flew off in all directions. I battled the situation by stamping on the bits of Parquet flooring that were the most alight. The master wet the floor and we swept the water into a dustpan and washed it down the sinks. After some time we felt it safe to go down to the dining room. I sat on a table cross-legged wondering why my feet were smoking.
In those days, we didn't throw good crepe-soled shoes away until our socks were showing through. I scraped and washed the soles time and again but as soon as they were dry, they started to smoke. Not very much now, but too much to be allowed in the house. They lived in a box outside the front door for some time.
People not believing my tales do not remember the war. We dreamed of owning crepe-soled shoes.
I took a classmate, the one that got me into the flying game, to see the master. He was in his 90's and had been on telly talking about blowing up a Woolf bottle while making hydrogen. I related the phosphorus saga. "I wish I'd told that story, it's a lot funnier."
That was three statements of no particular worth.
Bereft of empiricism, one had to invent ways of learning. In one of my early jobs there was a huge battery charger for customers that had battery radios. I connected an electrolytic with a working voltage of ~ 25v across a 100v supply. The plastic sheath over the aluminium case started to bubble. I became concerned for my safety and backed out of the tiny workshop. There was an almighty bang, and one could barely see across the room for a snowstorm of electrolyte. One has to be careful with the pressurising of electricity into small places on a reduced timescale.
Just as an aside. In the same workshop, I connected a little glass neon bulb across the mains - without its resistor. My little girly scream was more to do with the fear of being blinded than the very loud crack. I ran out of the room into the arms of my old science master, a man that had seen me blow a lump out of the high Victorian ceiling of the science room, before, during a nightschool lesson, setting the room on fire. He just rolled his eyes. Some things are not going to change.
I didn't get into trouble about the fire. He'd given the nod to me holding a piece of phosphorus over the Bunson flame. Flaming bits flew off in all directions. I battled the situation by stamping on the bits of Parquet flooring that were the most alight. The master wet the floor and we swept the water into a dustpan and washed it down the sinks. After some time we felt it safe to go down to the dining room. I sat on a table cross-legged wondering why my feet were smoking.
In those days, we didn't throw good crepe-soled shoes away until our socks were showing through. I scraped and washed the soles time and again but as soon as they were dry, they started to smoke. Not very much now, but too much to be allowed in the house. They lived in a box outside the front door for some time.
People not believing my tales do not remember the war. We dreamed of owning crepe-soled shoes.
I took a classmate, the one that got me into the flying game, to see the master. He was in his 90's and had been on telly talking about blowing up a Woolf bottle while making hydrogen. I related the phosphorus saga. "I wish I'd told that story, it's a lot funnier."
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Originally Posted by PDR1
You can't, not without massively compromising efficiency. Voltage across a capacitor is directly proportional to the charge. If you pump current in to charge it to (say) 100volts then when you take half that charge back out the voltage becomes 50 volts. So if you want to get 90% of the charge out at a consistent voltage you would have to charge it to 100v and then take the energy out via a 10v regulator. Even as a switched-mode regulator that's never going to be efficient at high power levels.
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Originally Posted by PDR1
All the elements with the highest positive (anode) electrode potentials are metals - lithium, potassium, calcium, sodium etc. So the highest energy density-cell is always going to use one of these as the anode.Metals are heavy,
PDR
PDR
...and there's relatively little of it in a Lithium cell. Pure Lithium depositing on the anode is one of the things you don't want to happen.
Last edited by netstruggler; 9th Apr 2021 at 07:29. Reason: grammar
