Nearly all modern phones, tablets, and laptops today use Lithium ion or the essentially similar Lithium polymer cell chemistry.

Here's some useful info about how they work and how to get the most from them.

Number of charges you can expect

A "charge" means the time and power it takes to perform one full, complete charge from 0 to 100% SoC (State of Charge). It does not mean how many times you plugged your phone into a charger. Anything less than 0 to 100% would be a partial charge.

So, for example, let us assume your phone is advertised to allow "500 charges" before any noticeable degradation. That's 500 charges from 0 to 100%.

If you always plugged in at, say, 50% SoC and charged to 100%, then that's half a full charge so you'd get 1,000 such charge cycles before noticing any degradation. Similarly, if your phone is at 75% SoC and you topped-up to 100%, that charge session would count as 1/4 of a charge. That's because 75 to 100 is a 25% charge, so 1/4 of a full charge.

Google your device's make and model number to see how many charges you can expect. There's waaaay too many to include here.

How to extend overall battery longevity

Here's several things you can do to extend overall lifetime / longevity of the device's battery. This advice specifically applies to the various Lithium flavors

• Don't let the battery SoC dip below 10%.
• Don't let the battery sit at or near 100% for a long time, either. That puts additional stress on the cells.
• Don't fast charge when a slow charge will do. e.g. Overnight, your phone will completely charge up in just 2-4 hours on a slow charger. Use fast charging only when you need a quick top-up, like when heading out the door soon. The way you control this is by having two chargers: A slow one that maxes out at 5 W and a fast one.
• Don't charge when your phone is hot. If it feels like a handwarmer then let it cool a bit before plugging in.

None of these things will immediately degrade your battery. But the more of these you violate and the more often you do so, that's when you start chipping way at overall longevity.

If you follow the advice above on a phone or tablet, it'll quite likely last until you'd otherwise replace it. Laptops are generally relevant from a performance standpoint for a lot longer, so the chances of reaching battery end of life are a bit greater.

Over Charging

I'm often asked about this. The device's BMS (Battery Management System) will not allow the battery to over charge so no worries there. The battery isn't going to overheat* or worse because it was left plugged in for a week or three. But as long as your device is plugged in, then the SoC will remain at or near 100% even while using the device. And as discussed above, staying at or near 100% for long periods isn't great for longevity.

* Batteries can overheat and possibly burst for other reasons. But an otherwise healthy battery will not do this just because it was left plugged in.

Memory Effects

Only you, ahem, older people, like me, will have experienced this.

The memory effect is when you repeatedly follow the same or similar shallow discharge pattern many times. e.g. Always discharging your device by only 1/3rd then recharging to full. After doing this enough times, the battery begins behaving as though that 1/3rd is its entire range. Then when used beyond that point, output voltage can drop which then appears like a flat battery to the device. The usual advice to prevent the memory effect was to discharge until the device stopped working (or nearly so) and perform a full charge.

The above applied mainly to NiCd (Nickel Cadmium) batteries and a little bit to the then-newer NiHM (Nickel-Metal Hydride) batteries that followed.

Today's lithium battery chemistries are not prone to memory effect. Shallow discharges don't hurt them. In fact, lithium batteries generally prefer shallow discharges over deep ones. But it's not a big enough difference that you should only ever perform shallow discharges. Lithium batteries are far more tolerant than older chemistries.

The main, best advice for lithium is following what I discussed under "How to extend overall battery longevity" a bit farther up.

Customizable Max Charge

For a few years now, laptop makers have included on most models a setting that lets you control the maximum SoC. Phone makers were a bit late to the party, only starting to include this feature in the last year or two. iPhone had dynamic charging features for several years. One of them was waiting until a couple of hours before you normally rise in the morning before finishing the charge to 100%.

But only very recently did Apple introduce a custom setting where you could choose your max charging level.

So unless you are truly away from any means to recharge during the day, then I recommend setting the max SoC to 80%. If you are anything like me, then chances are good you are generally near a source of power at home, in your car, or at work.

e.g. I have magnetic phone mounts with inductive (wireless) charging on my desk, nightstand, and in the car. So my phone is pretty much always at 80%. I put the phone on the mount and it starts charging. No cables to fuss with. About the only time when it's not plugged in is while visiting clients or out and about. For my laptop, I also keep a charger in its bag.

This feature isn't set automatically. And how to access it depends on the device type and brand. You can Google that. Look for "charge to 80" followed by your device, without the quotes.

Replaceable AA and AAA batteries

Some devices, like computer mice, TV remotes, and other small devices might have user-replaceable AA or AAA "penlight" batteries. I strongly recommend using Energizer Ultimate Lithium batteries -- not alkaline or any cheaper type of battery.

Why?

Alkaline and cheaper batteries are prone to leakage, leaving corrosion and gunk inside the device's battery compartment, and possibly damaging the device itself.

Energizer Ultimate Lithium batteries, on the other hand, rarely, if ever, leak. Yes, they do cost more. If the gadget is a cheap toy, then might not be worth it.

You might also consider using Panasonic Eneloop rechargeable AA and AAA cells for devices that rapidly consume batteries. You'll save money in the long run and not contribute to landfill waste.

Power Banks

Portable battery banks are pretty popular today and are great on trips when you might need your phone a lot more and are away from electrical outlets for a long time. They're a lifesaver when flying or when on vacation and visiting many new places, especially if you aren't renting a car. Your only reliable mains power might be at your accommodation at night. So bring along a power bank for charging on the go and keep it charged as well every night.

Anker is a reliable brand of power banks and they come in many sizes and power capacities. Search on Amazon.com