I mean.. if you say the character wouldn't explain it himself, and you'd rather not split his backstory into pieces sprinkled out in the plot or leave some of it for the readers' interpretation.. it sounds like you're pretty set on making the backstory chapters a thing that need to happen.
Backstory chapters are fine! If anything, it seems like you're under the impression that they'll harm your story in some way. I believe there's instances where delivering it all in one go is the best approach so that you can present everything necessary to understanding a character, so honestly, you can go with your gut on this.
My only advice in all this is to know when is the best time to share that character's past in full detail. Ideally, you'd wanna put it in between arcs so that while the story's not progressing much, at least it won't come to a screeching halt during important events.