]If mentioned 18650 has built in protection circuit, then you can parallel connect another 18650 with built in protection circuit with same capacity, same life and same state of charge. Another world, two 18650 cells both protected can be connected in parallel. Never connect unprotected to protected.Hi, I have a great camping lantern with one rechargeable 18650 (with protection circuitry). To increase run-time, is it likely that the protection circuitry could handle another 1860 in parallel? Thanks, SB.