Hey guys! I’m pretty young (15) and whenever I would get a new device for my bday or something, my parents always said that you needed to charge the device for 24 hours before you use it, and that you should always charge it up to 100% and use it until it hits 0% otherwise the battery won’t hold as much charge as possible. This kind of sucked because I of course wanted to play whatever it was right away instead of waiting until the next day, and I recently found out that you don’t have to do this on newer batteries but on older ones you do, which is how this “common sense” advice originated. However why did old batteries need to be charged for 24 hours before use, and used from 100% to 0% as it doesn’t seem like that should impact how much charge the battery can hold. Please ELI5.
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That battery chemistry, Nickel-Metal Halide (NiMH), was most stable in an uncharged state. That extended the life of the batteries, at the cost of needing to charge before first use. Almost all rechargables today are lithium based.
Old batteries can fall below a certain normal voltage that it’s meant to be useful at. If you were to put full recharging current through an undervolted battery, it would usually just result in damaging the battery. A very low current is used to very slowly bring the battery up to its operating range and then normal charging still needs to occur.
This was true of old nickel metal halide (NiMH) batteries back in the day.
Most devices these days use lithium ion batteries. They do not like to be fully discharged, or stored unused at >90% charge. They are happiest the closer they are to 50%. Most devices are designed to shut off before the battery fully discharges, and they set some limit before 100% charge as “100%” to prevent you from over-charging (this is less of an issue with things that are being constantly discharged, like a phone that you rarely shut off). Consumer electronics today are designed for you to not have to think about it or game the system. Just plug in when you want, and use it until you can’t (or plug in again).
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Old NiMh and NiCad batteries suffered from what’s called a “memory effect.” If you didn’t fully discharge the battery regularly, it would start to think the level you stopped at was its new “zero” and would slowly seem to lose charge capacity even though the battery was fine, just stupid.
So the full charge and discharge out of the box was to “set” what the max and fully discharged point of the battery were to make it so the memory effect would take longer to start.
Later generation NiMh chargers would fully discharge the battery before starting to charge it up again to prevent memory effect from taking hold, which took longer to do. There was a rule of thumb about using fast-chargers X number of times, which would only charge from the current level to 100%, then do a “full” charge to refresh the memory effect.
This is what your parents grew up with regarding rechargeable batteries, and was pretty common until the early 2000’s, when LiIons started showing up in laptops and cell phones. LiIon batteries changed all of this, but come with a different set of tradeoffs.
Edits: Added NiCad and revised a bit for clarity.
Batteries are tough. They all look the same on the outside, but the inside chemistries can be wildly different. The end result is two outwardly identical cells that should be treated in vastly different ways! It’s important to know what’s inside if one wishes to get the most out of their batteries and maybe even more important, to know which one to buy for your particular application!
One of the reasons to charge older style chemistries for long periods of time is because you want to make sure that you get them use to taking the most possible charge. If you don’t then you can reduce their capacity right out of the box. One of the reasons to long charge modern cells once and a while is to make sure groups of cells remain balanced.
I’ve lost track of what the proper rule is for batteries these days. I’ve heard it all: charge it fully, only charge to 80%, keep it charged, no don’t do that you’ll overvolt it, you should fully discharge before recharging, etc. I give up.
They didn’t need to be charged for 24 hours lol. They just needed to be charged until full and then drained until empty. They had a “memory” so in order to get the most use out of them on a single charge you needed to use the whole range to establish said “memory”. Most devices charged in like 5-6 hours so after that they were good to go. Most people didn’t understand exactly why though so you ended up with stuff like this. “Charge to full and drain to full so that it lasts longer”. I remember having devices that I’d use while plugged in constantly like a laptop and then once unplugged I’d be lucky to get 20 minutes of time. Replaced the battery and only plugged it in at sub 10% and unplugged at 100% and the battery would give me 2-3 hours every time. Old battery tech
That being said a LPT back in the day would have been “if you’re giving your kid something that needs to charge, precharge it for them so they can use it right when they get it”. As it is when we got my nephew his new Xbox for Christmas. I hooked it up and put the game he wanted most for it in the night before and got it ready to play then packaged it back up. When he first hooked it up to play instead of a bunch of downloads and patches it was just ready to go to start playing.
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