When referring to "80 battery health," it's unclear what kind of battery is being discussed, but assuming that we are talking about a rechargeable battery in a device, 80% battery health typically means that the battery has degraded to 80% of its original capacity.
The lifespan of a battery depends on many factors, including usage habits, environment, and the quality of the battery itself. Generally, a battery's health will degrade over time, with the rate of degradation depending on the factors mentioned above. Assuming a normal usage pattern, an 80% battery health should still provide several hours of use, but the amount of time will ultimately depend on the device itself.
To get the most out of your device's battery life, it is recommended to avoid charging it to 100% and letting it drain to 0%, as this can accelerate battery degradation. It's also advised to keep the device in a cool and dry environment and avoid exposing it to extreme temperatures or direct sunlight.