is there any issue doing this?

all batteries are the same.

looking to run two batteries in parallel.

I have three batteries that were purchased at the same time, and one purchased a few weeks later, but is the same specs/make/model.

the older batteries have had maybe one charge/discharge each.

they are turnigy 4000mah, 20-30c, 3s.

not that it makes much difference though

thankyou!