The big questions about how to re-charge a battery is whether you should let it run to zero before re-charging to 100%. One reason why people are unsure is something they’ve heard of called the battery “memory effect”.
What is battery memory effect?
Battery memory effect is about batteries remembering remaining charge if you don’t let them go all the way to zero too often. So a battery frequently charged from 20% to 80% might ‘forget’ about the 40% that’s left uncharged (0-20% and 80-100%).
Sounds crazy but that’s sort of true – but only for older nickel-based (NiMH and NiCd) batteries, not the lithium-ion batteries in your phone. Lithium-ion (Li-ion) batteries don’t suffer the memory effect so you almost need to do the opposite: charge them often but not all the way throughout the day, and don’t let them drop to zero.
The rule with Li-ion batteries is to keep them 50% or more most of the time. When it drops below 50% top it up a little if you can. A little a few times a day seems to be the optimum to aim for. But don’t charge it all the way to 100%. It won’t be fatal to your battery if you do a full recharge – most of us are forced to do this every now and again in emergencies. But constantly doing a full recharge will shorten the battery’s lifespan.
So a good range to aim for when charging a Li-ion battery is from about 40% to 80% in one go. Try not to let the battery drop below 20%.
Dead battery charge indicator
When should I do a full battery charge?
Experts recommend that you do a full zero to 100% battery recharge (a “charge cycle”) maybe once a month only. This recalibrates the battery – a bit like restarting your computer, or, for humans, going on holiday! The same goes for laptops, by the way.
Should I charge my phone overnight?
Most modern smartphones are clever enough to stop charging when full, so there isn’t a great risk in leaving your phone charging overnight. But some experts recommend you remove the phone from a case if charging for a long time, as a case could lead to over heating – which Lithium-ion batteries do not like