Why are we not already able to “instant-charge” EVs, smartphones or other batteries?
In: Physics
The best analogy I’ve seen is that a battery is like a car park. To charge it, you have to park all the lithium ions on an electrode, but there are only so many spaces for the ions to fit. Just like when a car park is busy, it can take the ions some time to find a space, and it gets more difficult the closer you get to fully charged.
12 watt-hours is a typical capacity for a cell phone battery.
To recharge a battery that size from empty to full in one second would require 43 kilowatts. Basically the same as a car charger (ignoring all the power conversion that would be necessary)
Imagine if you had to shove a Tesla plug into your phone…
Batteries don’t actually store electricity. They store energy via chemical reactions. These reactions are typically exothermic and can actually be quite harsh on batteries.
Lithium batteries in particular are surprisingly sensitive and require special charging algorithms and processes to not experience a thermal runaway.
With the current technology, the bottom 80% of the battery can be bulk charged really fast, in a matter of sometimes _minutes_, and some smartphone manufacturers do this if you have a power supply that’s beefy enough. It’s just a question of managing temperature while pumping in current, and this part of the charge cycle is pretty simple. Damage in this phase still builds over time, but it’s manageable within a normal life cycle.
The top 20% is where lithium batteries are more sensitive and require extra attention to avoid damaging the structure of the anode, cathode, and electrolyte. or triggering a thermal runaway.
This is why your phone seems to charge really quickly at first and then really slows down, still taking a full hour to charge to 100%. This also applies to EV charging, but quite often the bulk charging phase is limited by the capability of the charger instead of the battery, especially with active cooling.
Can you instantly fill a bathtub with water?
Are you asking why it takes time to recharge a battery and can’t be done instantly?
If so, then think of a battery as a bucket with very thin sides. If you slowly add water to the bucket it will fill up and hold all the water. If you blast the water in as fast as possible you will damage the bucket because the sides will fail due to the force and it won’t hold any water.
The slower you add the safer it is.
It kind of like the “pick 2” thing. You can have it cheap, be fast, last a long time, be efficient, you cant have it all
Because the storage and movement of large amounts of electrical energy produces massive amounts of heat, and when current gen battery tech gets hot it explodes.
Ideas such as supercapacitors and such are out there, but they haven’t actually been invented.
So we charge batteries at the highest current level we safely can, and that means long charging times.
We actually have things capable of ‘instant charging’: Capacitors.
Granted, they’re not as energy dense as batteries. But their use could be expanded into some more areas if we wanted.
That aside. Think of the logistics of ‘Instant’ charging a car. A 100kW/h pack would need to be hooked up to a 100kW charger for a full hour to charge up. To get that charge time down to a half hour, it would need something that could supply 200kW continuously. If you wanted 15 minutes then a 400kW supply is needed. That’s larger than the supposedly ‘future proof’ 350kW chargers that are the current big boys on the block.
Let’s jump ahead. To get to a sub minute time (which I assume is good enough to meet the definition of ‘instant’), you need a plug capable of delivering ~6.4 MEGAWATTS OF POWER. Basically you need to plug directly into a power plant… for one car. Good luck lifting that cable. Now multiply that one monster energy pump by every single car that needs to juice up.
There are super capacitors that can charge in a second or two. And they are pretty awesome, not sure why they aren’t used more.
batteries explode if you put too much energy into them too fast. in modern batteries it takes time and heat for the chemical reaction that stores the energy to happen, if you go fast the battery heats up and may get damaged, if you go even faster it explodes.
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