John the Geek

Is your laptop battery just not holding a charge anymore? And it’s only a year old? Sound all too familar?  Have you asked yourself is this because of a defective battery or a defective laptop?  Honestly more likely the answer is neither.  More likely it’s user error.

I find most people, even many technology professionals themselves, don’t truly understand how battery technology works, and as a result, often don’t understand how to properly charge and maintain their own fleet of batteries.  If you’re not getting at least 2 to 3 years of use from your rechargeable batteries, this article is for you!   A properly maintained rechargable battery should provide at least 2 years but more likely 3 to 5 years of useable, trouble free life.  In this article we’ll focus on the more common types of rechargeables used in modern consumer electronics, particularly laptops — the Nickel Cadmium (NiCAD), Nickel Metal-Hydride (Ni-MH), and Lithium Ion (Li-ion) type rechargeable batteries.

The analogy I always like to use to explain how to charge a Nickel Cadmium, Nickel Metal Hydride,  or Lithium Ion type battery is to compare how you refill your gas tank for your car.  To avoid running out of gas and getting stuck in the middle of nowhere, you would be wise to not wait for your tank to reach empty before refilling it.  Instead routinely refilling it at about the halfway level is wise.  In actual practice you could refill your gas tank at any time and it wouldn’t harm or degrade your car’s performance in any way.

But how you charge your battery does matter.  Following the same practice of recharging a battery that is only partially discharged is actually a bad idea.  A very bad idea indeed!   Here’s an important point to remember: It is actually harmful to the life of a battery to recharge it when it is only halfway discharged. 

Battery power is not derived in the same way as the power for your vehicle.  Unlike that gas tank which doesn’t care at what point you refill it, the power created inside a battery is actually a chemical reaction involving the transfer of electrons from one side of each battery cell to the other.  The recharging process helps to “reset” those electrons and ready them for the next time you need power delivered to  your favorite toy.  To prolong the life of your battery, it is actually best to run it down to as close to empty as possible before recharging. 

NiCads are notorious for what’s commonly referred to as the “Memory Effect”.  Overtime, if you continually recharge your battery when it is only halfway discharged eventually your battery will “remember” that halfway mark and will not be able to discharge beyond it.  Which means you will eventually lose all that original headroom.  So your battery will effectively lose half it’s charging capacity, and you will no longer be able to recharge it fully — it will only charge 50% of when you bought it.

Same thing holds true for a laptop that is always plugged in to the wall charger and never allowed to discharge.  That, too, is not a good practice and in a similar way leads to a “memory effect”. 

So best practice when it comes to recharging a battery is to actually allow that battery to fully discharge (not quite to totally dead but just before the “dead” mark), and then recharge it fully (back to 100% capacity).  Partially charging a battery is just as harmful as partially discharging, so don’t use a battery, charge it for a while, then use it some more, then recharge for a bit, etc.   Your battery needs to be fully discharged and then fully recharged to maintain the full capacity of it’s “fuel tank”.

Also, it’s best charge your batteries regularly.  If you let a rechargeable battery sit idle for a long period of time, the chemical process occuring internally will breakdown, and the battery will essentially “die”.  It will be unable to hold a charge or be recharged.  So even if you don’t use a battery for a long period of time, my advice is to recharge it every 6 months or so even if you aren’t using it.

Finally a word about the difference between the NiCad and newer Ni-MH type batteries.  The NiCad is probably still the more common type of battery in use in portable electronics and is most prone to the memory effect described above.  But the Nickel Metal-Hydride is quickly gaining in popularity over the Nickel Cadmium.  One reason is that the Ni-MH type of battery is not supposed to suffer from the memory effect to the same degree as the NiCad, but my advice to you is to treat a Ni-MH battery the same way you would a NiCAD.  By that I mean fully discharge it and then fully recharge it before reusing, just as you would a NiCad. Following this simple practice will extend the life of your rechargeable batteries to between 3 -5 years easily.