Q: How can I check battery health on 4S?

I have an older iPhone 4s.  It appears lately to need to be running down like its being drained more, but few if any apps running.  I try to turn off wifi when not at home so it won't try to connect to ones I can't use.  But the battery I'm sure could be just petering out.  How can I check to see how healthy it is?  I am running iOS 9.3.5.  I don't run Location Services for ex.  But mostly asking how can I see how many times it's been charged, or is there a good free or paid app that will tell me its health?  May look to buying new phone 5 or higher at some point but can't yet.