Guess it was my time - 12v is dead

[Dave Cundiff]

Maybe, maybe not...
You can charge a bad 12V battery to 14.6 volts then stop the charge, with no load on the battery it will still stay up around 14.2V and the vehicle would think the battery is okay. But, if it's truly bad, as soon as you put a load on it that 14.2 volt reading will drop like a rock because the battery is shot and has no ah capacity. In this case, the vehicle was fooled in to thinking the 12V battery was good.

Isn't the voltage/load curve under discharge conditions fairly testable, within voltage ranges that don't endanger the car's function?

Newbie here, so go ahead and educate me....

Thanks!

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[Rivianready]

I was actually looking into hooking up a powered subwoofer when I read your post. The car stereo installer said they would have to hook up the amp directly to my 12v battery and he took off the plastic cover in the frunk just below the windshield to look at the battery. It looks like there are two batteries, but I could be wrong. They look like small motorcycle batteries but they are not. From what we could see they are long and relatively thin for a vehicle battery. It was probably designed specifically for the Rivian. The installer said that because of their size he was uncomfortable with the draw an amp would make. Now I’m concerned that if I put any more load on them they will go bad. Why they didn’t put a regular sized 12v battery Rivians is beyond me.

 

[NY_Rob]

Isn't the voltage/load curve under discharge conditions fairly testable, within voltage ranges that don't endanger the car's function?

Newbie here, so go ahead and educate me....

Thanks!

A bad battery could drop to unrecoverable voltages very quickly under load in which could brick the vehicle.
I you look at the battery manufacturers spec sheet for the battery, they will specify the discharge rate and cutoff voltage that "should" result in the battery producing the advertised amp hour capacity of the battery. If for instance it's an 18ah battery, the manufacturer could specify a 1ah load which in theory would indicate an 18hr long test which would deliver 18ah at the end of the test. You have to refer to the battery manufacturer's spec sheet for every battery you want to test.

In any case, it's not really a test the vehicle could accurately perform and return meaningful results.. mostly because it can't chance running the battery down to 10.5 volts or so.

 

[NY_Rob]

Why they didn’t put a regular sized 12v battery Rivians is beyond me.

Supposedly, Rivian has said they went with those two small batteries because they couldn't fit one larger battery in the space they allotted for the vehicle 12 volt battery, so they went with two smaller 12 volt batteries.

That design decision has turned out to be one of the poorer decisions Rivian has made.

 

[Steve A.]

A bad battery could drop to unrecoverable voltages very quickly under load in which could brick the vehicle.
I you look at the battery manufacturers spec sheet for the battery, they will specify the discharge rate and cutoff voltage that "should" result in the battery producing the advertised amp hour capacity of the battery. If for instance it's an 18ah battery, the manufacturer could specify a 1ah load which in theory would indicate an 18hr long test which would deliver 18ah at the end of the test. You have to refer to the battery manufacturer's spec sheet for every battery you want to test.

In any case, it's not really a test the vehicle could accurately perform and return meaningful results.. mostly because it can't chance running the battery down to 10.5 volts or so.

Well, since the battery pack charges the 12V AFTER it's started, could the software run such a test and then charge it back up, esp. when the original Rivians had two 12Vs?

Find it hard to believe this is an engineering bridge too far.

 

[RexRemus]

I would agree, just the fact it is still communicating with the app indicates it is not dead.

It's not though. This seems like it's final send-off message. It's not communicating this is just the last reported state.

It's not charging per schedule, it's not unlockable or anything via the app. And it was unresponsive to the key card that I was able to have a friend try to see if it would unlock. It appears to be "dead".

I get back around midnight tonight and I'll be able to take a look at it Thursday. Already have a ticket with SC but we both want to assess the actual current status of the vehicle before taking any next steps.

 

[RexRemus]

The tub can stay in place. The 12v batteries are accessible without removing the tub.

Good to know thanks

 

[juancoffee]

I called the service center when I got that warning and couldn’t book it in for weeks because of a tight diary.
They said I was fine to continue driving it.

I did so, and it was fine.

 

[NY_Rob]

Well, since the battery pack charges the 12V AFTER it's started, could the software run such a test and then charge it back up, esp. when the original Rivians had two 12Vs?

Find it hard to believe this is an engineering bridge too far.

You certainly wouldn't want to run that test while driving... everything but the drive motors run on the 12 volt bus, if the test "fails".. surprise

 

[RexRemus]

Try their mobile service. They repaired mine the day I called. They can get into the drink via a latch cord under the driver side front wheel. They use a T20 or T25 to get I there and pull the cord. Then they can reach the battery by removing one panel over the frunk. The frunk does not need to come out. This is all doable in a tight space.

The passenger side of the frunk is completely unreachable without like... Crawling into the frunk itself. Which is absolutely doable if needed. So one side is accessible (drivers) but if they need to get to the passenger side it'll be silly. I mean, worth it, whatever it takes, because a tow isn't going to happen otherwise (if it comes to that), it's just gonna be silly. I'll request their smallest tech be sent ?

 

[Steve A.]

You certainly wouldn't want to run that test while driving... everything but the drive motors run on the 12 volt bus, if the test "fails".. surprise

Obviously, I wouldn't want to run that test while driving but It sits at home plugged into my Rivian charger 10-12 hours/day. Feel free to allow the test then and even better, feel free to make so that the home charger can actually charge the 12V too! ;-)

 

[NY_Rob]

Obviously, I wouldn't want to run that test while driving but It sits at home plugged into my Rivian charger 10-12 hours/day. Feel free to allow the test then and even better, feel free to make so that the home charger can actually charge the 12V too! ;-)

Yes, no reason Rivian couldn't come up with software to do that as it does keep track of the load on the 12v battery.

 

[Chewy734]

The passenger side of the frunk is completely unreachable without like... Crawling into the frunk itself. Which is absolutely doable if needed. So one side is accessible (drivers) but if they need to get to the passenger side it'll be silly. I mean, worth it, whatever it takes, because a tow isn't going to happen otherwise (if it comes to that), it's just gonna be silly. I'll request their smallest tech be sent ?

I’m pretty sure that being a contortionist or gymnast wasn’t in the job description for these mobile service jobs, but perhaps it should be? ?

 

[Steve A.]

The passenger side of the frunk is completely unreachable without like... Crawling into the frunk itself. Which is absolutely doable if needed. So one side is accessible (drivers) but if they need to get to the passenger side it'll be silly. I mean, worth it, whatever it takes, because a tow isn't going to happen otherwise (if it comes to that), it's just gonna be silly. I'll request their smallest tech be sent ?

Actually, my tow truck operator just hammered some plastic skates underneath my R1S rear tires and dragged it up onto the flatbed, so yeah, it can be towed otherwise.

 

[simpsonhomer]

Actually, my tow truck operator just hammered some plastic skates underneath my R1S rear tires and dragged it up onto the flatbed, so yeah, it can be towed otherwise.

Yeah, the same thing was done with my R1S to drag it out of my garage. This video shows the method used for me (but on a Hummer EV in the video):

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