Why are we not already able to “instant-charge” EVs, smartphones or other batteries?
In: Physics
Batteries work using a chemical reaction. That reaction has limits to how quickly it can proceed. You just physically can’t try and push energy in faster. Also there’s thermal issues because trying to charge too quickly will cause the battery to heat up above sage limits.
Batteries have an internal resistance. When electricity moves through resistance it generates heat. The more electricity you move, the more heat is generated.
One of the main limiters on battery charging is heat. Charge a battery too fast and it will over-heat. That results in fires or explosions.
To instant charge a battery we either need to be able to dissipate the heat very quickly or reduce the internal resistances so they don’t generate as much heat. Developing that capability is an area of significant research right now.
Battery technology is a balance between six different factors:
– Power capacity
– Physical size
– Charging/discharging speed
– Number of charge/discharge cycles before significant degradation
– Propensity to explode
– Cost
Getting all six in balance is tough – it is easy to focus on one or two at the cost of the others, but consumer electronics need all six. A battery that ~~maximizes~~ optimizes all six is the holy grail of battery science.
To your question, instant charging would create a ton of heat (electrical resistance) and that heat will damage the number of charging cycles and/or increase the propensity for the battery to explode. Neither is acceptable – the exploding thing is obvious, but no one wants a battery that charges in seconds but can only be charged a few dozen times before it no longer holds a charge.
Battery tech is only so advanced. It’s gotten insanely better, but trying to discharge a capacitor into a large battery to ‘quick charge’ it in a sense can cause some hefty damage.
Had a conversation about this with electrical engineering professor and suprisingly modern batteries are able to take this much power, but it’s not practical. In smaller scale, the biggest problem is heat and with electric cars our infrastructure isn’t capable for instant charging
There’s two problems with this idea. First, let’s understand what electricity is: the flow of electrons. For simplicity, imagine a wire as a hose carrying water. Imagine a battery as a bucket.
There’s a max rate for how much water your hose can deliver per second. The same is true for the wires in your home: there’s a max limit to how much power they can deliver per second.
There’s also a max rate for how much water a bucket can take per second. If you exceed this rate, then you end up spilling water instead of getting it into the bucket.
But this metaphor breaks down: electricity is much more complicated that water. Electrons repel each other. They don’t want to be packed together. The more electrons you have in a material, the harder it is to put more in there.
The way we pack lots of electrons together is through a variety of chemical reactions, which can only occur at specific rates. Going too quickly can cause the chemical reaction to fail to execute in some of the battery, leaving empty capacity and possibly damaging it permanently.
If you try to fill a battery up too fast, it overheats and can even catch on fire.
Note: we are actually moving “ions” around to charge batteries, not just packing in electrons, but for the sake of ELI5 I’ve simplified a lot of concepts here.
There’s one way to instant charge: just replace the battery.
Used to be a thing when phone batteries were still removable.
The faster you want to charge something, the higher current you need.
High currents make things very hot.
Very hot things are dangerous, especially very hot flammable things.
Elon Musk in a podcast with Joe Rohan has a great explanation of battery charging. Look it up, it’s a great analogy to cars in a parking lot and the charging process.
Batteries are chemical energy storage. When you discharge a battery, there is a chemical change happening inside the battery. As that happens, heat is generated. If you allow the chemical change to happen too quickly, the reaction goes out of control and the battery catches fire.
When you charge a battery, you are reversing the chemical reaction that occurred during discharge. Again, the limiting factor is heat. If you try to reverse the reaction too quickly, heat will build up and the battery will catch fire.
It’s kind of like baking a cake. You mix up the ingredients, and put the cake in the oven at 350°F (176°C) for 30-45 minutes. If you tried to double the temperature and half the time, you’d end up with burned cake batter.
Charging a battery is similar. The chemical changes need time to interact as the battery charges. Going too quickly changes the reaction to something else.
Latest Answers