Yes, but it carries a kind of dismissive connotation, especially for new users. I’ve only seen the phrase “carry around a brick” used by people who don’t like rechargeable aids.
Imagine if I were to refer to carrying around a pack of batteries as “carrying around a brick”. I’d hear back from folks!
all that said, I looked up ‘brick’s’ use as slang and found it tended to bounce between two extremes, in terms of meaning: here are two, following one after the other:
7 That’s not a mobile phone, it’s a brick.
8 You can always rely on Charlie, he’s a real brick.
I don’t think most folks here are referencing how reliable rechargers are when carried around as emergency back up for hearing aids. I think they’re gesturing towards, 'sheesh, who’d want to have to carry around am unreliable brick when instead they can carry a pack of batteries?. But in fact the two are essentially equivalent.