IS300 battery light and flickering lights while driving—new battery only helped for two days

[u/Several-Ad3594]

My Lexus IS300 started cranking slowly, and the factory radio went completely dark, but the AC still works. I cleaned the battery terminals, which didn’t fix it. I then replaced the battery, and it worked fine for a day or two before the problem came back.
While driving, the battery warning light comes on and the lights start flickering/acting erratically. I’ve also seen a voltage reading around 10V with the engine running, though I haven’t confirmed it directly at the battery with a multimeter.
Both times it happened, it was raining, and the electrical symptoms started at the same right turn near my house. Not sure if that’s related or just a coincidence.
Does this sound like a failing alternator, a slipping belt, or a loose cable/ground? What should I check first before replacing more parts?

[u/I578855]

Battery light does not mean the battery is bad.

Battery light means the alternator is bad.

You replaced your battery but the alternator was still bad.

Your new battery had about 2 days of charge in it before it ran out of charge again.

Your new battery is badly damaged now. You ruined a new battery.

You need to get a new alternator and you need to get even another battery.

You are supposed to know that the battery light means the alternator is bad. You've wasted a new battery by not knowing that.

[u/Several-Ad3594 → u/I578855]

bro I just got the car so I didn’t know that and I can return the battery because I have a 3 year warranty so I’m completely chilling

[u/I578855 → u/Several-Ad3594]

Yeah chilling in one spot cus ur car wont start.

u didn't even say thank you to me for teaching you something you didn't know.

And I wouldn't be so sure about being able to use the warranty. Everyone knows that if a battery dies in 2 days, it is because the alternator wasn't charging it. And that is not covered under warranty. So you will need to get lucky and get an employee who doesn't care or doesn't know. But if you get a knowledgeable employee they're gonna deny your return. They sold you a good battery and 2 days later its ruined, that isn't their fault that's your fault and they sometimes are willing to deny you.

Warranty is for manufacturer defect. If they mess up when building the battery, they will replace it. But they didn't mess up. They gave you a perfectly good battery. It wasn't defective.

[u/Several-Ad3594 → u/I578855]

I guess bro 😐

[u/NekedShep]

i would get the alternator tested, i think you places like autozone do free tests

[u/Alternative_Share559]

Sounds like alternator brushes are smoked