If you buy a second hand or replacement battery for your notebook, it's good to know how much juice is left both in the old and the new ones.While you can resort to an internal Windows 7 powercfg -energy command and report to analyze it, you had better install a dedicated utility.
Try one of these two:
- BatteryBar, from Osiris Development. Even its freemium version shows the "battery wear" parameter:
- Or try the bundleware BatteryCare:
After hot-swapping the old and new batteries, you can easily compare their specs.
For comparison's sake, here are the ones of the new replacement battery for my Lenovo X61 that I have bought off Ebay:
Usually notebook batteries lose 2-4% of their original storage capacity every month. Thus in 2 to 3 years time they will loose the capacity to store most of the juice and need to be replaced and properly disposed of.
If you want to prolong the useful life of your batteries, do not expose them to moisture or heat, e.g. inside your car under sunlight. See here for more than you may wish to know about proper battery care.
