If you are facing slow down or battery life reduced more then 50% then what you were getting. You might be infected by Malicious cryptomining. Malicious cryptomining is when someone else is using your computer to mine cryptocurrency like Bitcoin. This program utilizes full CPU power which leads to poor performance, PC keeping hot and draining battery life. Often using the Windows Task manager is enough to identify the culprit. Check out which program is taking most CPU power sometimes the name of programs might seem to be legit.
So if you found one, killing the process will not help as it might get alive again. Better to install latest Anti Virus solution. Also, don’t visit sites which you are not sure of, as most of the time infection happens by browsing fishy sites like torrent search engines.
If you are using google chrome add No Coin extension which will block coin miners using your computer resources without your consent. You can install by clicking on this link: https://chrome.google.com/webstore/detail/no-coin-block-miners-on-t/gojamcfopckidlocpkbelmpjcgmbgjcl/related?hl=en
for Firefox you and use following addons https://addons.mozilla.org/en-US/firefox/addon/no-coin/?src=search
So keep your PC safe from Malicious cryptomining. If you have any question do post it in comments and we will get back to you.