Buy a charger car for my iphone

For iPhone 8/X, the difference between regular charging with at least a 12W charger and “fast charging” (18W or more) is 50% (12:18 ⇔ 100:150). E.g. you would get the same charge level for 45 minutes in 30 minutes, if you would use “fast charging” (YMMV). You will have to decide if that gain is worth anything extra to you. Still cool that it can do it, though.

You will not damage the battery for charging it; you are meant to do that. However, the life span of a battery can be expressed in (full) cycle counts, meaning excessive power use will shorten the life span: the phone battery of a gamer will not last as long as the phone battery of a user that mainly uses low energy apps.

It is not significantly harmful to leave the phone longer on the charger, or more frequently, or “fast charging” vs. slow charging. Even the “fast charging” is throttled down to regular charging automatically, when it reaches 80% charged, which I presume is for safety reasons, and to keep the battery healthy. It is also advised to not completely deplete the battery level to 0%; start re-charging a bit earlier.

Either go for the “fast charging” option with at least 18W on the USB-C (USB-PD) port option (and extra Lightning-to-USB-C cable), or don’t bother with “fast charging” and use the regular USB Type A port.

For USB-C, I would go with the RAVPower 45W car charger. (The Anker 54W has more ports, but is also more expensive.) (The RAVPower 24W 2 port USB-C + USB-A maxes out at 5V/3.0A on the USB-C port, giving only 15W, which is less than the 18W you should aim for.)

For USB-A, there are some options that include a Lightning cable. That might actually be handy, so you can leave the original iPhone cable at home. Again, it is up to you, if that fits your routine. You pay for it, but not as much as an extra cable from Apple would cost. The RAVPower with cable seems like a solid choice.

For USB-A without cable, i.m.o. the choice is Anker PowerDrive 24W Dual USB in black or white, or RAVPower 24W Dual USB in black, red or gold, or smallest RAVPower 24W Dual USB.

With these, you get 5V×2.4A=12W per port.