[Silver Sipper]

I had the Check Brakes warning message come in today and the car wouldn't start. After checking a few things and trying to stop/restart/waiting about 10 minutes I rolled up the windows and was preparing to call AAA for a tow, when I started thinking the windows were going up a bit slower than normal.
Long story short, the 12v battery was drained after my son sat inside listening to the radio for about 35-40 minutes before his baseball game. Got a jump from a friend and drove it home.
I'm assuming that the lower voltage in the 12v battery wasn't enough to get everything up and running and it threw out the check brakes code. I think it would have made more sense to indicate that the battery voltage was low. I didn't have my meter, but it was at 12.4v when I got home.
Hopefully this will help someone out!

 

[MButkus]

Original battery ?
Shouldn't die after 35 min of the radio. Was the key on and fan and other accessories ? ?

 

[mogelijk]

Original battery ?
Shouldn't die after 35 min of the radio. Was the key on and fan and other accessories ? ?

I also can't help but think that the 12V battery should have recharged when the car was switched on, even if the car didn't fully start. I'm thinking the battery likely needs to be replaced.

 

[Fishnrib]

When I listen to the radio for a long time I start the car like it says. It will run in EV until it gets down to about 32% battery then starts the ICE until about 42% which lasts about 2min then repeat. You won't waist much gas doing this. You can save some battery if you turn off the display after starting the radio.

 

[Silver Sipper]

Now that I think about it a bit more, I think the climate control was still in auto so the fan was still running I believe.
I shut it down in neutral and shifted it to park to leave it in "accessory mode", so I think that was the issue.
Overnight it dropped from 12.4 to 12.3 and hasn't given me any issues since.

 

[HSHuser]

Thank you so much for your post OP, definitely saved me a tow for sure. Exactly same thing happened to me, waited for my son’s soccer game to be over (only about 30 mins) with the radio on, then boom everything went haywired. First it told me cannot detect key, then I inserted key and it told me to check Break, everything started blinking and going nuts. Finally I found your post so I called someone to help boosted the car and it was all good. Thanks again.

 

[George Monroe]

I had the Check Brakes warning message come in today and the car wouldn't start. After checking a few things and trying to stop/restart/waiting about 10 minutes I rolled up the windows and was preparing to call AAA for a tow, when I started thinking the windows were going up a bit slower than normal.
Long story short, the 12v battery was drained after my son sat inside listening to the radio for about 35-40 minutes before his baseball game. Got a jump from a friend and drove it home.
I'm assuming that the lower voltage in the 12v battery wasn't enough to get everything up and running and it threw out the check brakes code. I think it would have made more sense to indicate that the battery voltage was low. I didn't have my meter, but it was at 12.4v when I got home.
Hopefully this will help someone out!

Thanks for posting, I am new to the hybrid thing so this warning scared me this morning!!

 

[Fulchezy]

I had the Check Brakes warning message come in today and the car wouldn't start. After checking a few things and trying to stop/restart/waiting about 10 minutes I rolled up the windows and was preparing to call AAA for a tow, when I started thinking the windows were going up a bit slower than normal.
Long story short, the 12v battery was drained after my son sat inside listening to the radio for about 35-40 minutes before his baseball game. Got a jump from a friend and drove it home.
I'm assuming that the lower voltage in the 12v battery wasn't enough to get everything up and running and it threw out the check brakes code. I think it would have made more sense to indicate that the battery voltage was low. I didn't have my meter, but it was at 12.4v when I got home.
Hopefully this will help someone out!

This post just saved a life and cash in this pandemic, thanks for posting

 

[Martinkrvn]

This post just saved a life and cash in this pandemic, thanks for posting

Hi this just happened to me I was just wondering did you have to change the 12V battery after that or it was fine?

 

[jeepramnauth]

This just happened last night to me. Radio on, AC and headlights! Gave me same warnings, then boosted and all good. Will go check battery today

 

[gewb]

Similar situation last year. New battery from AdvanceAuto solved it (original was 5 yrs old). Paid around $180US which is a lot cheaper than Hyundai dealer price.

 

[Massguy]

I find that it doesn't take long for the low battery warning to come on in these cars. Sometimes it's after only 15 minutes. And that's with a fairly new battery. For other cars, I've gone over an hour without a problem. This is the only car I have a concern with when I goto the drive-in. I ended up buying a portable speaker for that.

 

[TJ31324]

I had the Check Brakes warning message come in today and the car wouldn't start. After checking a few things and trying to stop/restart/waiting about 10 minutes I rolled up the windows and was preparing to call AAA for a tow, when I started thinking the windows were going up a bit slower than normal.
Long story short, the 12v battery was drained after my son sat inside listening to the radio for about 35-40 minutes before his baseball game. Got a jump from a friend and drove it home.
I'm assuming that the lower voltage in the 12v battery wasn't enough to get everything up and running and it threw out the check brakes code. I think it would have made more sense to indicate that the battery voltage was low. I didn't have my meter, but it was at 12.4v when I got home.
Hopefully this will help someone out!

A month or two ago I got the "no key present" error. That turned out to be the 12V battery. Got a jump from AAA, had the battery checked out, and was told it was fine. Then I got the check brake, constant beep, won't start a few days ago. I thought it was something new (not happy!). I read your post and figured okay, I've been here before. I waited overnight (too cool down...me, not the car) and sure enough, now I got the "no key present" error, and knew just what to do. Got a jump, drove to the store, and got a new battery. Thanks for the post. I was prepared to tow it to the dealer to have them figure it out, but this saved me all that hassle.

 

[Fulchezy]

Hi this just happened to me I was just wondering did you have to change the 12V battery after that or it was fine?

No I did not have to and i have not changed the battery still since May.

 

[Frank Xu]

I got the same problem during lockdown! I panicked a little bit but quickly realize sonata hybrid is brake-by-wire and it could be a battery issue. I took my multimeter out, found that my battery only holds 9v. After recharge everything is fine.
BTW how much your battery voltage drops overnight? I got a new battery and it loses ~0.1v overnight. Is that normal?

 

[Ajoures]

Thanks. The same problem happened while waiting about an hour at CVS covid test parking. I was considering replacing my sonata hybrid. I wonder the weird noise from the dashboard could possibly have something to do with the weak battery too.

 

[Maria K]

I had the Check Brakes warning message come in today and the car wouldn't start. After checking a few things and trying to stop/restart/waiting about 10 minutes I rolled up the windows and was preparing to call AAA for a tow, when I started thinking the windows were going up a bit slower than normal.
Long story short, the 12v battery was drained after my son sat inside listening to the radio for about 35-40 minutes before his baseball game. Got a jump from a friend and drove it home.
I'm assuming that the lower voltage in the 12v battery wasn't enough to get everything up and running and it threw out the check brakes code. I think it would have made more sense to indicate that the battery voltage was low. I didn't have my meter, but it was at 12.4v when I got home.
Hopefully this will help someone out!

OMG! Thank you so much, I was just about to call a tow truck too. But I think when I moved my car in the snow storm I may have forgot to turn a light off or left it running or something. Either way, I'm 90% sure it is my battery now.
Thank you!!