10mo ago

Why Charging Your Gadgets Over 80% Is Such a Bad Idea | iFixit News

www.ifixit.com Why Charging Your Gadgets Over 80% Is Such a Bad Idea | iFixit News

When we think about battery longevity, we think about charging cycles. But that’s not the whole story.

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I don't like this article because it misses some of the more important details around how to lengthen your device's life and why you may or may not want to keep your battery at a specific state of charge.
State of charge is pretty arbitrary, your charging circuit could charge between 3.0V and 4.2V (pretty typical), or it could charge between 3.2V and 4.0V and still show 4.0V as being 100% charge. Different chemistries can have slightly (or significant in the case of LFP) different voltages. The cynic in me wouldn't be surprised if eventually 100% becomes ~4.35V because it makes their device look better to tech reviewers, but then have it default to only charge to 4.2V because it still gives suitable device life.
The most important factors in how long your device's battery will last are temperature and how deeply you discharge the battery. Discharging your phone down until it dies does way more damage than keeping it charged at 100%.
At some point practicality comes into it, you would get even more total energy out of a cell if you kept it between 40% and 60% all the time, but obviously it isn't very practical to only use 20% of your phone's available capacity in day to day use.
Consider how long you are storing your device. If it is always plugged in or won't be used for months, then something like 40% to 60% would be a more suitable state of charge to keep your device at if possible. If it sits on your desk and you need to unplug it periodically and know you don't need the full charge, then sure keep it at 80%.
Personally, I don't stress about the batteries in my devices at all. I generally keep an eye on the power and plug it in when convenient, but target plugging it in before it gets too far below 50%. I've historically had almost zero issues with the batteries in my devices wearing out before I'm ready to replace it for other reasons unless it started out with marginal battery life.
- Yep. Battery chemistry is a real pain in the ass. Every few years someone spins a wheel and determines the next big thing that everyone needs to do to prevent batteries from dying early. For a while people were told full cycles were healthy for avoiding cell memory. Now more sporadic cycles are being peddled.
  Use the device as you need it. If you complete a full cycle, cool; if not, that's fine. Just don't let the damn thing completely die and don't keep it permanently on charge. Those are the common things most people do on accident that can really screw up a cell.
  
  It isn't spinning a wheel though, the advice hasn't changed in decades (I've written something like the above comment at least a dozen times on Reddit since 2008 when I worked in the industry). Rather you might be getting it confused with other cell chemistries. Memory is a problem for NiCd cells, which were popular a long time ago, but even once we moved to NiMH for most things and then Li-ion there is no concern about it. Unfortunately there is a ton of incorrect and bad information out there about batteries so it is hard to wade through the crap and find the real information.
  https://batteryuniversity.com is the best resource I know for correct information about li-ion cells, since it is written and maintained by a company that designs battery testing equipment.
  
  Part of the problem is the game of telephone drops the cell chemistry related to the method almost immediately leading to general consumers applying it as a blanket rule for all batteries
  Interesting source though...
- About 4, I'd start long term storage from 80% because self-discharge rate is 30% per year in room temperature, or 15% per year in the fridge, which is the best storage temperature. Also, Battery University said in some article that 65% charge is optimal for storage, which is ~3.95V/cell at rest for most chemistries.
  
  The reason I said 40-60% is because over that entire range both self-discharge and permanent capacity loss happen at their slowest rates because that is the flat range of the voltage curve where the cell is close to its nominal 3.7V voltage. The self-discharge with starting at 80% will maybe buy you an extra couple months before the cell becomes unusable, but you would experience more irreversible capacity loss.
- Yeah, that's been my whole experience surrounding people being upset that batteries aren't able to be replaced in phones anymore. Don't get me wrong, I'm not saying it's a good habit, but I've never had a phone long enough for the battery's life to degrade to the point where that degradation was more than mildy noticeable.
  
  Maybe that says more about your phone consumption than battery life.
  I try not to buy a new phone every year and I can tell you, after 3-4 years, the batteries are very noticeably dying. My last two phones (nexus 4, moto z play) both were replaced due to failing batteries, since replacing them is almost impossible (I couldn't even find replacements that I would call trustworthy).
  My usage was not super unusual, and most days I plugged them in over night and that's it.
  
  It can also depend on the device. I've had smaller devices and have had to charge multiple times a day. After getting a bigger phone with a bigger battery. I simply don't think about it anymore. I imagine my phone dying before the battery does or even if it does, I'll pay for a replacement if needed. I'd rather not stress in the day to day.

256 comments