nitecore and l91 lithium battery

Noticed on going gear website the ea42 specs says l91 not recommended. Any idea why?

Voltage. L91 = 1.8v, EA42 runs the 4xAA in series so you’re actually gonna be supplying it 7.4v.
It’s a buck driver but some component on it probably has a 6vin max or something.

Just looked on energizer website and they list it as 1.5 always heard were higher. And I don’t have one now to measure.

They’re 1.5v nominal but the initial voltage is 1.8. Just like NiMH is 1.2v nominal but actually 1.5v off the charger…

See hjk’s review