Are You Charging Batteries The Wrong Way?

Category: Mobile

“My phone is dead.” How many times have you said or heard that one? Running out of juice in the middle of the day is frustrating. But maybe you're part of the problem, without even knowing it. Now, here is a different approach to charging the battery in your mobile devices…

A Better Way to Charge

Part of the problem is that each generation of mobile devices has more features that consume battery power. GPS, accelerometers for fitness tracking, sensors for this and that, brighter and bigger screens, etc., all take their tolls on batteries.

I discussed several ways in Boost Cell Phone Battery Life to reduce power consumption. Those tips concerned how your usage habits affect battery life. But today, we'll look at what happens when you plug in to the charger, and reveal a method to optimize both the runtime and the lifespan of your battery.

The manner in which you re-charge a Lithium ion (Li-ion) battery affects both the amount of power it can hold over the long run and how long the battery will last before it must be replaced. It turns out that many users re-charge batteries in ways that are suboptimal.

Charging Lithium Batteries the right way

The battery engineers at Cadex Corp. host a site called “Battery University” where the insatiably geeky can explore the wonders of electrochemistry in great detail. Much of the information I present here is distilled from their page on charging Li-ion batteries. I’ve tried to keep it simple.

Many users have the mistaken notion that a Li-ion battery should be fully discharged before it is re-charged. This myth may be a carry-over from older nickel-cadmium batteries, where so-called “deep discharge” does have some uses. It may also be simply a rationalization of our forgetfulness towards plugging in a charger.

Sip, Don't Binge...

In any case, a Li-ion battery should be re-charged in small bursts or “sips” of electricity, not one long binge feeding. The latter method puts a lot of “stress” on the battery and diminishes its capacity over time.

Leaving a Li-ion battery plugged into its charger after it is fully charged is also wrong, yet it’s the most natural thing to do at the end of the day. Just plug your phone in when you go to bed and unplug it in the morning, right? But the battery doesn’t just go to sleep when it’s fully charged.

Batteries lose tiny amounts of power just sitting there. When a plugged-in battery loses charge, it replaces it by drawing brief “trickle charges” from the source of electricity. This frequent on-off cycle stresses the battery and reduces the number of times it can be re-charged.

So the ideal method is to unplug the charger when the device indicates it is fully charged, right? It turns out that’s wrong, too.

“Li-ion does not need to be fully charged, nor is it desirable to do so,” says Battery University. “In fact, it is better not to fully charge, because a high voltage stresses the battery" and reduces its lifespan.

Happily, the right charging strategy is not difficult to follow. Just plug in your device whenever you can throughout the day and you’ll be fine, say the Cadex experts. Ideally, a Li-ion battery should be plugged in when it loses 10 per cent of its charge, but that’s not practical for most of us.

Most people are too busy to constantly monitor the state of the battery in their phone or laptop. Even those who have the time and patience to do so may not have convenient access to a charger at all times. But whenever it's possible to implement, the charge-when-you-can strategy is close enough to ideal and will preserve your battery’s capacity as well as its lifespan.

Your thoughts on this topic are welcome. Post your comment or question below...

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Most recent comments on "Are You Charging Batteries The Wrong Way?"

(See all 36 comments for this article.)

Posted by:

Robert A.
28 Jul 2016

This seems like a good argument for getting a two-year contract on a phone rather than buying it outright, since the battery, with all the recharging, is likely on its last legs, by then.

Posted by:

28 Jul 2016

Is there no end to the ways I am doing things wrong? :)

Thank you Bob for enlightening me on yet another topic.

The Battery University page made me realize once more how great, and simplified, your articles are.

Posted by:

28 Jul 2016

I refuse to think about charging batteries.
There! I said it, and I'm glad.

And plugging the charger's stupid USB cable into the phone is a giant pain in the seat cushion.

Posted by:

28 Jul 2016

This is not my experience. I find that if I charge my battery to between 80% and 95% and then use it, I get much shorter life than if I leave it on charge overnight. I also find that completely discharging my battery about once a month seems to give it a new lease on life.

Posted by:

David Lagesse
28 Jul 2016

There are FREE apps that will alert you when your battery is fully charged, and some of those apps will alert you on a USER-set percentage of charging.
Just look for 'Battery' in the App Store.

Posted by:

28 Jul 2016

I have & use "smart" charger/surge protectors, and love them. One side is constant current. The other side intermittently checks the plugged in device for need to charge, then either charges or withholds current until a need to charge is found.
There is an override button to cause immediate charging on the "smart" side. Very easy & dependable.

Posted by:

28 Jul 2016

Bob, Thank you for a very informative article on the proper procedure for charging batteries. I learned a lot!

Posted by:

28 Jul 2016

Sounds like frequently plugging in to one of those portable battery rechargers would be a good solution.

Posted by:

28 Jul 2016

Bloody hell. So instead of your phone being just a practical tool to use, and recharge overnight when it makes perfect sense (to the user) it has now become an adult version of those bloody stupid tamagotchi keyring pets. So perhaps that's what they were about? To train the next generation to serve their machines, instead of the machines serving them.


Posted by:

Dexter Gondo
28 Jul 2016

Please comment on the Tesla Coil Power pack offer

Posted by:

Jay R
28 Jul 2016

And I thot the care and feeding of Japenese knives and the necessary water stones was a murky and complicated affair. All of a sudden this is simple when I think about charging my battery.

For me, the real question is this. (If I am very CDO about the charging stuff, there will still be times when Acts of DOG happen and my battery will die. Or I forget that I have plugged it in when the next client has a cardiopulmonary arrest.) How many screw-ups are allowed before I have done the vampire thing with my battery and put a steak in its heart? 3 screw ups and I'm out of luck?

Posted by:

Stephen Hedge
28 Jul 2016

Very interesting to know after using the NiCad method of recharging. A little and often will be the new method from now on.

Posted by:

Dave Campbell
28 Jul 2016

There should be no reason for a charger designed for lithium-ion batteries to go into "trickle-charge" mode. Lithium-ion batteries *do not* lose their charge just sitting on a shelf.

Call me cynical, but I suspect manufacturers know their current charging method is bad for the batteries and that's how they get us to buy new phones. (After "I need more storage," I would bet "my battery doesn't hold a charge" is the next most-often cited reason for "needing" a new phone.)

Posted by:

28 Jul 2016

Thanks Bob, I've been wondering about exactly this question.
I have a Samsung Galaxy S6 which comes with a fast charger. I wonder if the rules are any different for using this charger than the normal rate.

Posted by:

29 Jul 2016

Thanks for the distillation. I believe I had that site up one time which if digested should earn a PHD. I have a really interesting story about the newer smart NMH and charger but it would be off-topic here.

Posted by:

29 Jul 2016

Totally opposite of what I've thought. I've been doing the drain it and leave it on the charger over night thing for years. I'll make this change. Thanks for the article.
Cheers, Guy

I have been doing the same thing as Guy. Thanks Bob for this information.

Posted by:

05 Aug 2016

I have been thinking about this and was wondering... If the batteries have a set number of charges in them, how does the "sip method" impact this?
Thanks as always for great, practical information.

Posted by:

07 Aug 2016

Thanks again Bob! I have been doing this exactly wrong. As I'm sure many others could say, I'm a hold over from the NiCad days and carried those habits with me. It's going to be hard to make myself change but I know that the phone is off the charger tonight at least.

Posted by:

Mike B
24 Aug 2016

Hi Bob,
I have a simple suggestion on which I would like your opinion please. If I use a timer on my Vodafone Smart Phone 6, will I prolong the life of the battery? What I have in mind is to set the timer for , say, 40 to 60 minutes, and commence the charge at about 15% capacity- would this be a pretty simple solution to the over-charge problem? One could go to sleep happy that the phone would not be over-charging after about 90 minutes.

Posted by:

01 Dec 2016

I think the battery university needs to go to a university school to learn what they are talking about. I have never heard such bull-crap in my life !

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