Depends somewhat on cell quality. My Neuenergy lipos balance down to a few mv. My oplder Neus show imbalance of 2-5mv, the newest ones right now are holding less than that. My IP lipos don't do as well, they show 5 to 10mv differences. I have some no brand 18th scale lipos I got as part of a trade and the worst among them shows 40-60mv imbalance.

My hyperion internal balancer is +/-5mv across the cells and its never had any prob doing that and has never needed more time than the regular time to complete a charge.