I have a 2009 Sonata with 142K miles on I think the original alternator. When I start the vehicle, voltage displayed on the Scanguage 2 shows above 14 volts, but after the car gets warm, voltage drops below, down to 13.4 sometimes. I think I have even seen less than 13 volts a time or two. Is this an indication of a fault alternator or voltage regulator?
Less than 14 volts while running
- Thread starter Shaman
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Normal
Sounds normal?!?
It's normal for the voltage regulator to reduce the voltage to a "float" level after the battery reaches a high state of charge. This prevents the battery from boiling off electrolyte due to overcharging. Just to give you an idea, if a battery has 200 amps drawn from it for 2 seconds to start the car and the alternator pushes 20 amps back into the battery when the engine is running, then it would only take a little more than 10 seconds for the battery to recover the discharged current.
Check the voltage of the battery after letting it sit 24 hours. If the battery reads between 12.6 and 12.7 volts, the alternator is working normally. If it's lower, then you may have a worn/weak battery or low alternator output.
Check the voltage of the battery after letting it sit 24 hours. If the battery reads between 12.6 and 12.7 volts, the alternator is working normally. If it's lower, then you may have a worn/weak battery or low alternator output.
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Like other members have said this is actually normal.
My car on the scanner live data shows 12.88 volts to 13.12 volts routinely while running.
Quite interesting. Surprised me too seeing that at first. I also think me having a very good battery in my car has helped me keep the original alternator and starter in my car too.
My car is a 08 Nissan Altima VQ. With 350k miles plus.
My car on the scanner live data shows 12.88 volts to 13.12 volts routinely while running.
Quite interesting. Surprised me too seeing that at first. I also think me having a very good battery in my car has helped me keep the original alternator and starter in my car too.
My car is a 08 Nissan Altima VQ. With 350k miles plus.
Just noticed a little problem with my math, LOL...
I figured it was normal, but wanted to make sure. That’s what I get for plugging in. The SG2.
Never underestimate the insanity of one's vehicle's voltage regulator.
Ignorance can indeed be blissful.
Ignorance can indeed be blissful.
My 09 Saturn is at 15.2 for a short while after startup. after that it goes all over the place.
Here's a thread I started about Hyundai's "smart" charging system:
https://bobistheoilguy.com/forums/threads/overriding-a-smart-battery-management-system.333405/
https://bobistheoilguy.com/forums/threads/overriding-a-smart-battery-management-system.333405/
this may/may not be a controversial Opinion....while normal, leisurely plan to change the alternator when you can.
Alternators are "wear" items and at that age can fail at any time if/when the alternator brushes get used up. and no one can know the condition of those brushes until the alternator is opened up.
ymmv.
Alternators are "wear" items and at that age can fail at any time if/when the alternator brushes get used up. and no one can know the condition of those brushes until the alternator is opened up.
ymmv.
Nick1994
$100 site donor 2024
I think it’s normal, here’s a thread I created about my 2015 Sonata a while back.
https://bobistheoilguy.com/forums/threads/sonata-strange-battery-charging-behavior.280323/
https://bobistheoilguy.com/forums/threads/sonata-strange-battery-charging-behavior.280323/
2018:Mazda 3 rarely gets into 13.75 volts and is stable at 12.65 with normal highway and low stereo volume to 12.35-12.65 . I also run a high energy sound system with the OEM alternator. That will soon changed to a healthy 125amps @ ideal of 650 rpm to 250 amp @ 1200 rpm .
Normal part of the RVC system which stands for regulated voltage control. Basically computer controls the alternator output to maximize fuel ecomony and battery service life. Sometime my CTS will run along at 12.8v. Good system so you're never overcharging.
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