Blizzard Like Storm Here in CO, bout 30 degrees outside. My wife left the headlights on for 7 Hours on my 07 Lexus Is250. I just replaced the battery about 2 months ago and I replaced the alternator as well. I let the car run for 30 minutes ( no issues starting it) to let the alternator try and charge it.. but realistically is my battery discharged already? Will driving the car just kill my alternator again?

 

Given the age of the battery and alternator, I’d hazard that they will be fine, but maybe suggest leaving the lights on “auto”.

 

Considering the battery is brand new, and the car started with no issues, it likely didn't cause any damage from the steady discharge. 30F is slightly below freezing so it's cold but not that cold.

If the battery was 2-3+ yrs old with a few winters under its belt already you might have an issue, but new batteries are fairly resilient.

Not sure if your comfortable, but you can test your battery under load to check its condition internally.

 

Thank you @Jeeves250 @SeanO I appreciate the info. Should I go get it tested at my local auto store where I bought it? I usually don’t like to do so because the teens usually don’t know what they’re talking about when they use their device. Should I also consider letting them charge the battery?

 

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The main thing to keep in mind is that 30 min will not undue 7+ hours of discharge as it's doing plenty of work to keep the occupants happy at those Temps while shoving so many amps into the battery.
A trickle over night may not fully restore it at those temps either. A good charger might worth the expense given the territory.

 

@2013FSport Thank you! I’ll start looking into a good charger

 

A good trickle charger will cost around $50. Well worth the investment. Wallyworld or Mazon. A rechargeable battery pack is likewise a good investment.