I've installed Elementary OS on a Macbook late 2009 in place of the High Sierra that had issues (sudden and frequent reboots), Now it works well, I like the look, but the battery that previously had about 20 min autonomy, drastically diminuished in a few days, now it's 1%, in practice it must be continuosly powered. In terminal lshw shows unknown battery, I wonder if the battery is OK only Elementary is unable to recognize it or is it ruined definitely. If the battery is ruined, I could buy another but surely don't want to ruin it too. Thanks in advance for any help
sudo apt install tlp && sudo tlp start
from terminal. If you want to finetune the settings follow this guide linrunner.de/tlp/introduction.html