Can I add 2 nwme ssd Storage Memory in my Acer Nitro AN515-45-R1SC?

The Nitro AN515-45 accommodates 2x M.2 PCIe Gen.3x4 type drives and Acer fits 2TB type drives also, but remember that M.2 slot #2 will never ever be as quick as M.2 slot #1 the boot drive, there will be a difference of about 28%+ or - between the two same drives (as having two different spec drives will be even more).

Any type of hard drive type limitations on capacities in Windows is only limited by what the drives are format with, MBR/Legacy is limited to 2TB max and GUID (GPT) NTFS type format has a so-called limit (as not many will use these levels) and can support volumes as large as 8 petabytes (1 Petabytes = 1000 Terabytes) at Cluster size of 2048 KB (max size) and Largest volume and file size of 8 Petabytes, which your total of 8TB should be comfortably within those limits😁

Your AN515-45 has an M.2 PCIe Gen.3x4 and not Gen 4x4 M.2, yes and it can be fitted with a Gen 4's M.2 drive but it will never utilize the Gen4 x4 read/write max speeds so remember that, At 4TB M.2 you are limited to what drives you can buy but the only current drive that I would consider as its very affordable to have in a 2x M.2s form in a laptop or desktop is the TeamGroup (see below) that is offering its PCIe Gen 4x4 - 4TB M.2 for $242.99 USD which is an unbelievable price and value.

At $275 the TeamGroup is an unbelievable M.2 PCIe 4 x4 drive value, as the Samsung EVO plus does not come in 4TB capacities only at a max of 2TB, so you only have very limited choices in 4TB capacities.

These are the Nitro AN515-45 Service Guide Acer specified specific 2.5" and M.2 SSD or mechanical HDD that are suitable for the AN515-45 as Acer lists the following specs,

1. SSD1 slot - 1x PCIe3x4 M.2 SSD drive
2. SSD2 slot - PCIe3x4 or a SATA III M.2 SSD drive
3. SATA III space - 1x 2.5” SATA III mechanical or SATA III SSD drive (see caption below of the listed drives) that are compatible,

Also note, that Acer only lists M.2 SSD drives that are of either 256GB/512GB and max 1024GB capacity which are either from Samsung/Kingston or SanDisk but they do list 2.5" SATA III drives of 2TB and that is why I will suggest that a 2TB M.2 SSD drive will work. I’ve also specifically highlighted the 1024GB M.2 SSD drives for your information. All in all, I personally would only stretch the capacity of the max capacity of 1024GB drives of both type M.2 SSD or 2.5" SATA III drives to a max capacity of 2TB and NOT to 4GB or 8GB.

Note: putting such an expensive M.2 SSD drive like a 4TB or an 8TB (the slots will support and these drives will fit) but I can't 100% guarantee that these drives will work, as I've never ever used them, but it will be very interesting to see if your Nitro AN515-45 will work with such high M.2 SSD capacity drives?

All I know that in theory and within windows, a storage and/or a boot drives capacity is governed by the format that is used, which in format MBR/Legacy the max capacity is 2.2TB and in format GUID (GPT) UEFI bios the max capacity is 8 petabytes (1 petabyte = 1000TB) so and what I'm saying in all the above is that theoretically the M.2 SSD 4TB and 8TB should work 100%, but you have to test the new M.2 SSD 4TB or 8TB out yourself and if these capacities work in your Nitro AN515-45-R1SC laptop? As I can’t guarantee that they will work, buy these expensive capacity M.2 SSD drives at your own risk. Good luck and hope I’ve helped you out in this regard.

All compatible and recommended Acer HDDs for the Nitro AN515-54

The below positions are where your boot and slave M.2 SSD slots for the AN515-45 are, both of this laptop Storage 1 and Storage 2 are PCIe3x4 type M.2 SSD slots.

Note: that the Gen 4 PCiE4x4 are backward compatible with your laptop, but and if you fit these Gen 4 PCIe4x4 M.2 SSD drives, then these drives will not perform at their peak speeds of sequential read of up to 7500Mb/s and sequential write speeds of 6500Mb/s but will perform at the PCIe3x4 M.2 SSD speeds of about max 3800MB/s sequential read and 3000Mb/s sequential write, which they will perform only their 50% speeds, so be aware of these differences in speed.

SSD1 BOOT M.2 SLOT - is between the 2.5" SATA HDD and the Wi-Fi/BT card

SSD2 SLAVE M.2 SSD SLOT - is on the other side of the laptop: