Is it possible to power the heltec v3 with NIMH batteries? Like maybe 4 in series (4.8v) or 3 in series (3.6v)?

Would it even charge them or is the charging only for li-ion battery packs like the 3.7v one that everyone suggests?

I don't want to buy it if I don't need it, I have old NIMH batteries in abundance and I'm not sure what my final setup should look like yet.