2009 4.6 battery light/battery issues

[nickdalman]

I have a 2009 Hyundai Genesis 4.6 V8 With 84500 kms or 52000 miles. Since our first cold day of -20 Celsius last week I found my battery died over night, I have been finding it dead every few days when I try to start it since then. I suspected I need a new battery and assumed mine is just weak and can't withstand the cold weather as its about -25 everyday now, but yesterday after boosting it in the morning yesterday AGAIN, the battery light came on when I was driving home. Now I am worried it is an alternator issue, or was the light just letting me know I need a new battery, has anyone had a similar experience? I just plugged it onto a battery charger before posting this and the battery light turned off and it started right up, so.. in summary I charge the battery or boost it, I drive for a day or two and the battery dies overnight in freezing temperatures. And I had a battery light come on while driving. Any ideas? I am confused on weather I should go buy a new battery today or go get the alternator looked at. V8 alternators are a $500 part before labour costs etc. and the car has very low kilometres, so I will be pretty pissed off if it isn't just a bad battery.

 

[joegr]

Your best bet is to measure the battery voltage while the engine is running. Between 13.8 and 14.5 V and you know the alternator is working. <13 and it is a problem for sure.

Here's one easy way to check.
https://www.amazon.com/INNOVA-3721-...words=car+battery+gauge&qid=1576510385&sr=8-7

 

[nickdalman]

So I picked up a new (aftermarket) battery, the battery light is on all the time now and won't go away........ while the car is running it reads at 14.70 V steady and doesn't drop at all so I guess the alternator works. When the car is off and my trunk is open it is around 13.30 V and does drop .01 V around every 5 seconds, would it be dropping because my trunk is open therefore a dash light and trunk light is on? It's at 13.15 V turned off and I am going to let it sit for an hour and see it drops. Still doesn't explain the battery light though.. I hooked it up properly.

And thank you for the response by the way it helped me out

 

[nickdalman]

Your best bet is to measure the battery voltage while the engine is running. Between 13.8 and 14.5 V and you know the alternator is working. <13 and it is a problem for sure.

Here's one easy way to check.
https://www.amazon.com/INNOVA-3721-...words=car+battery+gauge&qid=1576510385&sr=8-7

So after I installed new aftermarket battery, it runs at 14.5 V -14.7 V consistently so the alternator is good. The battery loses voltage after sitting with the car off, for an hour of sitting it went from 13.15 V to 13.6 V I think it was, I think that is because of the cold weather.

Everything works perfectly fine now so I don't know why the battery light WILL NOT turn off and I am getting the "don't use multimedia system without car running" message when the engine is running... I am going to bring it to the dealer tomorrow to have them make sure I hooked everything up to the battery correctly and see what they think. I'll update you on what they say

 

[JaeTeeBee]

OP, It sounds like it is most likely your battery if it just seems to fail to hold a charge. If your alternator is bad your car will die mid drive. It seems a common alternator issue after around 100k miles is that the pulley will separate from the internal rotor causing it to not generate electricity. If you truly have an alternator issue, your multimedia system will issue you a warning to "ensure your engine is turned on to prevent battery drain". Hope this helps!

 

[Kraig Wilkinson]

So after I installed new aftermarket battery, it runs at 14.5 V -14.7 V consistently so the alternator is good. The battery loses voltage after sitting with the car off, for an hour of sitting it went from 13.15 V to 13.6 V I think it was, I think that is because of the cold weather.

Everything works perfectly fine now so I don't know why the battery light WILL NOT turn off and I am getting the "don't use multimedia system without car running" message when the engine is running... I am going to bring it to the dealer tomorrow to have them make sure I hooked everything up to the battery correctly and see what they think. I'll update you on what they say

Sounds like the alt might be faulty? 14.7 is kind of high IMO.

 

[jjstolarik]

So after I installed new aftermarket battery, it runs at 14.5 V -14.7 V consistently so the alternator is good. The battery loses voltage after sitting with the car off, for an hour of sitting it went from 13.15 V to 13.6 V I think it was, I think that is because of the cold weather.

Everything works perfectly fine now so I don't know why the battery light WILL NOT turn off and I am getting the "don't use multimedia system without car running" message when the engine is running... I am going to bring it to the dealer tomorrow to have them make sure I hooked everything up to the battery correctly and see what they think. I'll update you on what they say

Did you ever get the battery light issue resolved? I have the same situation. New battery, new (rebuilt) alternator, good voltages, battery light still on.