What is the best way to extend the life of a laptop battery.

I have heard that rechargeable batteries last longer if they are completely discharged and then recharged rather than being left at, or near, full charge.

I normally use my laptop plugged into to AC power. Would it be beneficial to periodically run it on the battery and completely discharge it. Or just leave it fully charged. My goal would be to have maximum battery usage when I do need to run on it.

Thanks

Depends on the battery chemistry.

Li-Ion leave plugged in.

It does depend on the battery type. Now days most laptop batteries are LiIon and decay the slowest unused (Plugged in) or fully used, charge to dead. The same goes for many cell phones. However, if you are dealing with a PbAcid battery, like in most automobiles, then you will find it lasts longest when it doesn't discharge much; charging it slowly and never letting it die will make it last past the warranty.

PbAcid - depends

There are two types. The automobile and deep discharge. The latter has higher plate separation and higher series resistance.

It does much better at deep discharge, but still would prefer to be topped.