okay to fast charge an aftermarket battery?

[Threepwood]

so, I bought a second hand iphone 13 pro max for someone as a gift, it has recently had a new aftermarket battery fitted, I got a USBC fast charger for it, to go with the supplied, unused lightning cable
I plugged it all in, and it seems fine, the phone is charging, but it is getting pretty hot, I'm using the phone at the same time as it is charging, should I be worried and rush togo get a OEM battery fitted by apple, or am I good to go?
I think that i'm going to charge the battery down some then try and fast charge it, and, as long as it charges, and doesn' t blow up then I'm going to give the phone away as the gift, and not worry about it
what do you think?
TIA

 

[Threepwood]

I don’t think the aftermarket battery is the issue.

Fast charging will cause the phone to become warm even when idle so using it whilst on fast charge will only add to that.

The other factor is whether you are using a case with it as this will also heat things up

cheers, no case on it yet, that is part of the present, that they can put it on when they get it!
I drained the battery to 50% by putting the brightness on full w/ torch on and running youtube while we went to the supermarket, plugged it in to fast charge , and it is up to 72% in 25 mins (95% now after 1 hour), and it doesn't feel too hot to me, not even while using it at the same time I think that I'm good to go, maybe it just felt hot compared to my own phone idk, maybe I worry too much!
Must say that it is a lovely phone, the screen is really nice, but there is no screen protection on there yet, compared to my sony xperia 5ii, when that had no protector on it, I'd say that it is a dead heat, they are both OLED,so there is no real surprise there! full brightness was pretty cool though, on this iphone, very vibrant colours..
very happy with this ebay sniped item, it's a £500 phone for a £360 snipe, can't ask for more really, charger, and front/back sandwich protector for £20, I'm sure they will be very happy. totally worth it for 380 squids even in it's original box, very sexy!