| CPC G01N 21/59 (2013.01) [H01M 10/4228 (2013.01); H01M 10/48 (2013.01); H01M 50/3425 (2021.01); H01M 50/512 (2021.01)] | 10 Claims |

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1. A battery module comprising:
a battery stack in which a plurality of batteries provided with a valve that ejects gas are stacked along a first direction;
a discharge path that discharges gas ejected from the valve in a second direction intersecting the first direction;
a light emitter that is provided on one end side in the first direction of the battery stack and emits light to the discharge path; and
a light receiver that is provided on another end side in the first direction of the battery stack and receives the light emitted from the light emitter,
wherein the light emitter includes a light source and an emitting lens configured to adjust a light flux emitted from the light source to an arbitrary light flux.
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