To know the answer to that question, we need to know a little more about the personalities of a Lithium Ion or Lithium Polymer battery. These are the same exact types of batteries commonly found in your mobile phones.
How to make the batteries last longer per charge? How to prolong their lifespan? How to prevent having batteries explode in my face? These are important questions to us.
While the internet is a convenient tool, there are simply too many misconceptions about your smartphone batteries floating around on the internet. No thanks to the fact that Lithium Ion/Polymer batteries behave very differently from their predecessors, the Nickel metal hydride batteries that have graced the phones of yesterday years. If you have a Nokia 3310, the battery inside is a Nickel metal hydride (NiMH).
Because many people don’t really know the differences between the older battery types, they ended up giving battery advice that really harm your Lithium Ion (Li-ion)/Polymer(LiPo) batteries (I shall collectively refer to these as ‘Li’).
Bad advice are plentiful. Charge your phone for 6 hours before using? Only charge your battery when it is close to empty? These are just some of the advice that were perfect for NiMH batteries but will cause your Li batteries to suffer a slow, horrible death.
Back to the topic at hand. Should you charge your phone overnight? To answer that, let’s look at the summary of Li battery characteristics:
- Li batteries are afraid of heat. The higher the temperature, the faster it loses capacity over time.
- Li batteries are afraid of being empty. The emptier it is, the faster it loses capacity over time.
- Li batteries are afraid of being full. The fuller it is, the faster it loses capacity over time.
- Li batteries are afraid of being overcharged (charged more than full) or short circuited. If it gets charged too much, it gets bloated due to chemical reactions in the cell.
- Li batteries are afraid of being over-discharged (use more energy than the battery is willing to give). If it gets discharged too much, it gets bloated due to chemical reactions in the cell.
- Li batteries are afraid of being ruptured. If the internals are exposed to air, it catches fire and burn.
- Li batteries keep the scores well. If you charge from 50% to 100% twice, that is considered one charge cycle, not 2.
Expecting more? Nope, that’s all you need to know.
So overnight charging. Is it good or bad?
Let’s talk about safety first. Overnight charging is generally safe as long as your battery, charger and mobile phone are all from reputable manufacturers. Badly manufactured chargers and mobile phones may have overcharge protection circuit that fails, cause your battery to get over charged. When you battery gets overcharged, the internal cell undergoes a chemical reaction, and the battery start to bloat.
If the bloat is too much, the battery ruptures, causing the internals to be exposed to air, resulting in fire and explosion.
While this is still O.K. if you are around and can swiftly put out the fire or prevent the fire from spreading, leaving your smart phone to charge unattended isn’t safe. Your whole house would have burnt to the ground while you sleep.