For that matter what is it with batteries that make them so fickle?
You can’t charge them to full, but at the same time you can’t let them die, but at the same time you should wait for them to die before you charge since constant charging is bad, but at the same time not charging enough is also bad like what’s the real deal with batteries T_T
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The manufacturer also knows this, and puts the limit on in software and hardware systems – when your phone says 100% it is actually 90% or whatever limit the manufacturer set.
Just as an example.
Most batteries you can’t let die unless they’re user replaceable.
For example when a cellphone *dies* it actually has around 10-15% battery left. As a buffer to keep it protecting.
Charging to 100% hasn’t been an issue since we stopped using NICAD.
Most of what you’re citing is old information people still parrot because they don’t keep up with technology.
Not applicable now.
It like the old school, Slap the Side of your TV to fix it, nothing you slap is going to move inside of a TV in 2024, but shit moved inside of a TV back in 1994 when you slapped it, which could fix the picture.
The easiest explanation I’ve heard is that when charging to full, imagine fitting more and more people into a car. It’s easy at first, but once you start getting it closer to full, fitting those last few people (energy) inside is much harder and takes more effort. Which is stress on the battery.
Think of it like filling a balloon over and over.
Sure, you can inflate it to max every time, but each one will stretch and wear the balloon until it eventually pops.
Inflate it to 75% or 80%, though, and you’re going to get less wear and many more inflation cycles before it fails.
Honestly this advice is outdated.
It’s not at all a big deal anymore. The batteries have built in protections now that do a lot behind the scenes.
Just use your devices. You don’t need to baby the batteries.
batteries are sort of miraculous devices. there are only a few specific chemistries that are reliable enough that they’ve been adopted everywhere: lithium ion (phone), lead acid (car), and alkaline (AA), basically. this is 3 widely adopted out of thousands of potential chemistries. they are difficult systems to make work.
for why it’s bad to overcharge/overdrain them, there’s different reasons for different chemistries. you’re probably asking about lithium ion though, so it’s kinda like this:
to use a battery, atoms have to move across the battery. on either side, there are solid particles that can accept the atoms. this is a powder – on one side of a lithium ion battery it is literally powdered pencil lead.
the atoms in these particles happen to be structured such that they can gain and lose a certain number of atoms without the overall structure changing. you can think about a scaffolding, where you could remove some of the bars without the scaffold falling down, and add some bars as well, but too many or too few would cause it too collapse.
when you over-charge/drain, some of the particles lose or gain too many atoms, and the structure collapses and changes. when this happens, the atoms can no longer move in and out. the scaffolding has collapsed, and it is now difficult to remove a bar from the pile because it’s tangled up in the structure. atoms stuck on one side = fewer atoms moving back and forth = lost battery capacity.
that being said, as others have pointed out, advice to not leave things plugged in, not overcharge, etc, are remnants from before lithium ion. NICAD and NiMH batteries were used before lithium ion became the standard for lightweight, high performance uses, and they are far, far, far more tricky to properly charge. I can elaborate if you’d like. for long-term storage, it is indeed still better to store lithium ion batteries at medium charge and not plugged in. but for a battery that gets used even weekly it is not an issue.
As far as EVS go, it varies a little bit based on the battery technology. In general, And I say in general because technology is changing and your actual use case for the battery may make this more of a hassle, But you generally think of it like a balloon.
Yes, it’s capable of being filled to the point where it is full at its maximum design capacity. But if I want to fill this balloon a thousand times between now and 5 years from now, fully stretching it out and fully deflating it is maximum wear and tear on every square inch of it. If I can get away with just filling it to 80% deflating it 80% deflating it, etc, Long-Term health of the battery will be better as I’m not pushing its limits or stressing it as much.
That’s why most of your EVs default to 80% as a charge limit, but you absolutely can bump it up to 100% if you need it for a trip later. Just, long term, 100% without a real need isn’t the best idea.
I don’t think there’s too much issue with charging to 100%. Main concern is charging and leaving it at 100%. Or worse letting the battery die and leaving it dead for too long. You decide from there how much you want ideal charging to affect your life. My iPhone caps to 85. My car caps at 70. I only change it to 100% before a road trip
So first of all, the “never” is not true. It’s not actually a big deal to charge the battery to full or let it completely empty.
However, it does degrade the battery faster. But faster is also relative.
Basically, the charge level of a battery (any battery) affects the voltage it outputs. As the charge goes up, so does the voltage. As the charge goes down, so does the voltage.
When the voltage is high, it is harder to charge. This does a few things, including producing more heat, but the end result is that charging from 91-100% might put as much strain on the batter as charging from 70-80%. So you’re straining the battery more for less charge.
When the voltage is low, it is easier to charge but harder to discharge. So running the battery at 10% might pull a lot more power out in order to get enough voltage. This is why you will see your battery drop faster under 20%. It’s not that being low charge is bad, it is that you draw more power. Draining from 20 to 10% isn’t any worse than going from 80 to 70%. However, you might need to use 12% battery power at low levels for that same thing thst would only take 10% at high levels. This is what causes more wear.
Note that charging a battery at low charge doesn’t hurt it at all. In fact, it is much easier and better to charge at lower levels. This is why you will get really fast charging below 50%, which slows a bit until 85%, then slower charging above 85%.
Modern chargers actually “talk” to your phone or device and adjust the charging to be the most efficient. They also mitigate a lot of the problems discussed above.
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