Look, listen... dont mess around with that old Samsung brick because youre just gonna end up frustrated. Its like trying to put a generic oil filter on a high-spec engine... it might fit the threads but the flow rate is TRASH. That S21 charger is likely a Samsung 25W USB-C Wall Charger and it wont talk the right language to the OnePlus 13. Listen close because people get this wrong all the time. OnePlus uses SuperVOOC which is a proprietary handshake. Most generic PD chargers will default to a slow 18W trickle because they cant handle the high amperage. Your phone will take 2 hours to charge instead of 35 minutes. Here is what you actually need:

• The <a href=" https://www.ebay.com/sch/i.html?_nkw= OnePlus+100W+Dual+Port+SuperVOOC+Power+Adapter&_sacat=0&_from=R40&_trksid=p4624852.m570.l1311&mkcid=1&mkrid=711-53200-19255-0&siteid=0&campid=5337998953&customid=22&toolid=10001&mkevt=1" target="_blank" rel="nofollow sponsored">OnePlus 100W Dual Port SuperVOOC Power Adapter is the ONLY way to hit those peak speeds.
• You MUST use the official red cable because it has extra pins to handle the high current.
• Heat management is moved to the brick so the battery doesnt cook itself. If you use a generic block, it wont even TRY to go fast because it doesnt see the right encryption chip. Just buy the official <a href=" https://www.ebay.com/sch/i.html?_nkw= OnePlus+SuperVOOC+100W+Power+Adapter&_sacat=0&_from=R40&_trksid=p4624852.m570.l1311&mkcid=1&mkrid=711-53200-19255-0&siteid=0&campid=5337998953&customid=22&toolid=10001&mkevt=1" target="_blank" rel="nofollow sponsored">OnePlus SuperVOOC 100W Power Adapter and be done with it. Ngl anything else is a waste of money if you want that fast juice...

ngl that official 100W price is NUTS. I saved a ton by snagging a <a href=" https://www.ebay.com/sch/i.html?_nkw= OnePlus+80W+SuperVOOC+Power+Adapter&_sacat=0&_from=R40&_trksid=p4624852.m570.l1311&mkcid=1&mkrid=711-53200-19255-0&siteid=0&campid=5337998953&customid=22&toolid=10001&mkevt=1" target="_blank" rel="nofollow sponsored">OnePlus 80W SuperVOOC Power Adapter used for $20 instead of paying full retail.

• Check eBay for open-box deals
• Use a Baseus 100W USB-C Cable to save even more Store wanted $60 but I got it for $20. Saved me $40 which is basically a week of gas... kids dont need the absolute peak speeds anyway tbh.

Rarely post but—honestly—the brand doesn't matter—my cousin once tried a solar panel from his camping gear—wait, no, it was a lawn light—and his phone battery just swelled like a balloon.