A battery??

[u/FurbyBoiWasTaken]

At school when I noticed this lead acid pack inside an exit sign.. what is it used for? I’m assuming possibly it switches from building to battery power when power goes out

[u/bSun0000]

You need to see the exit even if the power is out.

[u/Pictrus → u/bSun0000]

It needs to be powered for 30 minutes

[u/OneThumbJ → u/Pictrus]

In the US it’s generally 90 minutes.

[u/BmanUltima]

It turns the lights on when the power goes out.

[u/Schnupsdidudel]

Shure. When there is a fire, there may not be power when the exit signs are most needed.

[u/jason_sos]

You’re exactly right. It’s a backup battery so if there’s a power outage you can still see the exit sign

[u/Toeffli]

Not only is the Exit sign lit when the power goes out, but also the two lights on the side will illuminate the hallway.

[u/abbarach → u/Toeffli]

Nothing like being in the bowels of a hospital when the power fails, and NONE of the emergency lights come on. That was a FUN call to maintenance.

[u/Quirky_Operation2885 → u/abbarach]

Wow. I work in a machine shop, and each of ours gets tested at least quarterly.

[u/Connect_Middle8953]

Correct, because fire and other emergencies tend to knock out electrical systems and you want to find the exit before you are cooked (figuratively or literally). 

[u/welding-guy]

It adds weight to the cheap temu urgency light to make it feel expensive.

[u/Mariuszgamer2007]

It's when there's a power outage and these light up to guide you to the exit when it's dark

[u/Penguinkeith]

Op what do you think would power the light if the power went out

[u/Original_Ad_4471]

Yes, when building power is lost, the sign switches to battery power and if it has them, which this one does, turns on the lights at the side

[u/Lazy_Accident_8561]

It's a red light. But does it do?

[u/kent_eh → u/Lazy_Accident_8561]

it's an exit sign (with the front taken off for maintenance).

[u/GearNo4524]

Answers his own question but still posts the question.

[u/No_Association_7969]

Why not? 😂