A fire and/or overheated condition detector for a lithium ion battery is provided. The fire and/or overheated condition detector includes a chamber defining a detection space fluidly communicative with an interior of the lithium ion battery, a temperature sensor operably disposed proximate to the detection space, gas detection assemblies configured to detect gases through absorption in the detection space and a smoke detection assembly configured to detect particle scattering in the detection space to discriminate smoke particles from nuisance particles.