Is it safe to use these chargers to replace my lost laptop charger?
Original charger: 19V, 4.74A
- Replacement 1: 19V, 4.5A
- Replacement 2: 20V, 4.5A
A replacement must be the same voltage. Too little, and the battery won't charge. Too much, and you'll fry something.
The amperage should be the same or higher. If it's too much lower, it either won't work, or the adapter will overheat making the attempt to power the laptop. If it's higher, the laptop simply won't use the extra available power.
Either charger should work fine. The only difference is it will take very slightly longer to charge the battery than with your original charger. There's no adverse affect on battery life from the lower amperage. IF anything it might last just a bit longer since the heat generated (and dissipated inside the battery compartment) will be slightly less. But we're talking a very small amount here - less than 1% I would think.