You can buy discharge protection modules fairly cheaply but I notice they tend to have discharge protection kick in at ~2.5 V. Isn't that already an over-discharged state for a lithium ion? I've read that a minimum voltage should be 2.8 or even 3.0 V. Are they expecting other circuitry to stop the voltage getting to this point in normal use? Is there an easy way to adjust the threshold by maybe just changing one or two components?