What do I do when my BP-511's are not holding a charge like they use to?

I have had some Sterlingteks for 2-3 yrs and they have worked awesome.
i have noticed recently that when i take them out of charger and put into cam they give me like only 300 shots then it is showing half power.
Besides buying new ones which I am not opposed of doing. what can I do to save them a little longer is there a way to recondition them or are they pretty much on their last leg.
thanks for any help

Do you get 300 then showing half power or 300 with half power? Do you have a grip? Older grips used to have a glitch where they showed fully charged batteries as running at half power.

Shoot and see how many shots you get until fully drained. May help fully draining and recharging from scratch.

What the battery meter shows and what the battery actually will deliver is often two different things. Sterlingteks are cheap....if you are in doubt...snag a fresh pair. If you are still getting 5-600 shots on a charge...that is certainly acceptable for a 3 year old battery.

They are Li-ions do lose capacity over time, one of my laptop's battery is completley useless as it takes longer to boot than its life