Apple isn't the only company whose smartphones have battery-related performance issues. Google's Nexus 6P device had similar problems - the difference between the two companies is that Apple mostly got away with a slap on the hand (by offering customers $29 battery replacements), whereas Google was hit with a class-action lawsuit.
For the unaware, battery defects within 6P devices caused the phones to randomly shut down or even lock users into unending boot loops. These issues were so widespread that Google has now essentially given up the legal fight, with it and manufacturing partner Huawei jointly agreeing to settle the lawsuit by compensating affected users.
Often, the largest chunk of a class-action lawsuit payout goes to the lawyers, with affected customers maybe earning some dinner money at best. This time around, though, as long as you can prove you were impacted by these issues (perhaps by providing documentation of email support requests), you could take home up to a whopping $400.
If you don't have said documentation, the best you can hope for is a $75 payout - that is obviously not chump change, but it's certainly a far cry from the full $400 sum. If you opted to trade your Nexus 6P in for Google's Pixel XL, your payout will be reduced even further; all the way down to $10.