I’m often asked whether laptop batteries need to be drained completely before recharging them.
My answer? Well, it depends on the type of battery that it uses.
Older laptops used nickel-cadmium batteries which were subject to a “memory effect”. If they weren’t allowed to discharge all the way before being recharged they would eventually “remember” the level of charge they fell to before recharging and act as if they were completely drained every time their charge decreased to that level.
This memory effect lowered the useful life of a charge dramatically, requiring the purchase of a new battery long before it should have reached the end of its useful life. Therefore, if you still have a laptop that uses a nickel-cadmium battery you should let it discharge completely before allowing it to recharge.
Newer laptops use lithium-ion batteries which work much better and last longer than their nickel-cadmium predecessors. First of all, they are not susceptible to the memory effect which means you can recharge them at any time. In fact, lithium-ions will last longer if you never allow them to fully discharge.
Another advantage of lithium-ion batteries is the way they hold their charge when the battery isn’t in use. The older nickel-cadmium batteries begin losing their charge immediately after being topped off, even if the laptop is turned off and not being used. Lithium-ion batteries on the other hand will hold their charge for months with only a very slight drop in charge level.
Bottom line: If your laptop uses a nickel-cadmium battery it’s best to let it discharge completely before recharging it. But if it uses a lithium-ion battery it’s best to keep the charge topped off.
To find out which type of battery your laptop uses, simply remove it from the laptop and take a look at the label. The battery type will be printed on it.