An EV for example: if the car has 10% charge left, does the battery have less power or amps or whatever than it does when it’s at 90%? Or an iPhone at 20% vs 80%…same question. Or, from the battery’s perspective, even to 1% left, it’s either on or off, regardless of charge remaining?
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The voltage drops as the battery runs down. That’s how your device knows what the charge is, it can tell that the voltage is dropping. 0% is the critical threshold where it drops below the voltage required to reliably power the device.
Most devices will actually power down before that happens so that the battery doesn’t fully discharge, so their “0%” isn’t truly too low to power the device.
No, they don’t! Different kinds of battery chemistry have a different “discharge voltage curve” where the voltage delivered will gradually drop off as the battery’s charge decreases.
You can look up graphs to show general trends of different battery types but something like lead-acid will be a steady dropping curve while lithium-ion tends to stay high then take a sharp drop off around 80% discharged.
All that being said there are ways to mitigate this (circuitry to normalize voltage) and there is no guarantee that something like a smart device is telling you the raw discharge potential of the battery. A smart phone is unlikely to let you discharge a lithium-ion battery all the way to zero, so it would likely show you 1% charge left around that 20% remaining before the sharp drop in voltage where it likely can’t effectively function. It would also likely have the smarts to prevent damaging the battery with excessively deep discharge or overcharging.
No, it doesn’t and in some cases that’s actually a way of measuring how much charge is left. A battery that is partially charged will have less voltage between the two poles.
How stable the voltage is depending on charge, is very dependent on the type of battery though, and from what I remember one of the reasons we use Lithium batteries is because their voltage output is very stable compared to how charged they are.
No it doesn’t, but depending on the application it might not matter. A electric car might have slightly lower acceleration on low charge, but unless you are on a racetrack you are unlikely to accelerate at max speed anyway.
The battery by itself, no. It’s been covered by other comments but I think I can add 2 things. 1, a battery stores energy in chemistry. There are reactants that react together to make products. The speed of the reaction basically defines the voltage of the battery (well, I guess current more directly and voltage indirectly, but it works well enough for eli5). The higher the concentration of reactants and lower concentration of products the faster the reaction runs. As the reactants get transformed into products, the reaction slows down, decreasing the voltage that the battery can maintain.
But the battery is no longer an isolated component in modern circuits. There is always a governing circuit. It’s often some kind of voltage regulator that can take a small amount of the energy to hold the voltage more stable. There are even boost circuits that can raise the voltage at the cost of current. So there’s a high likelihood that the rest of your circuit sees the same voltage regardless of the charge on the battery… As long as you don’t run it beyond the designed parameters. However, the governing circuit should also monitor the charge of the battery and stop the circuit from using more than it’s designed to. It can help monitor charging current too so that the battery doesn’t explode (hopefully).
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