12 volt system totally died, bricked truck... Still waiting for Rivian to review logs and tell me why!

[NY_Rob]

I could see that the battery charging system is on a roughly 2 hour cycle. When charging, the voltage reads 13.7v, then drops to just over 12v until the next charging cycle.

That might be one of the problems right there....
Lead/acid automotive battery charging circuits generally run up to 14.6V and are limited to that max voltage by regulators built in the alternator. If Rivian is only charging their 12V AGM batts to 13.7 volts that's far too low and leaving lots of stored energy on the table resulting in a very low state of charge even when "full".
The Rivian 12V battery even shows recharge voltage (14.1-14.7V) right on the side of the battery...

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[FNWY2004]

Dropping 2 charged lithium batteries in the spare tire well. If I get stranded, I could give no shits about a warranty if it can get me out of a jamb. Some ass covering can be to put a multimeter on the dead batteries and take a photo before changing them. Changing out two 12v batteries should have 0 impact and cause any problems with the warranty.

 

[Kidentist]

Wow......more issues.......

 

[NY_Rob]

^ this is an "old" issue from day 1 that still occasionally happens even today.

Rivian has actually done very little if any redesigning to correct issues that have plagued vehicles from VIN 1,000 on. Some of the software issues like the vents not keeping positions, gear guard dropping out, etc.. have been fixed.. but the old hardware issues that occured day 1 are still with us (and that's not encouraging).

 

[Rivinator]

That might be one of the problems right there....
Lead/acid automotive battery charging circuits generally run up to 14.6V and are limited to that max voltage by regulators built in the alternator. If Rivian is only charging their 12V AGM batts to 13.7 volts that's far too low and leaving lots of stored energy on the table resulting in a very low state of charge even when "full".
The Rivian 12V battery even shows recharge voltage (14.1-14.7V) right on the side of the battery...

Good observation! It sure got me curious, and after some digging I found the battery manufacturer manual RS02252_DCS_EV_Manual_202012.pdf (cdtechno.com) within it they list a recommended "float" charge of 13.50-13.80 at 25°C (77°F). What I'm measuring falls within that range, so all's good. But, what the heck is a float charge? It's not the same as a trickle charge as it turns out, and must be the type of system Rivian is using to keep the batteries topped off. I found an explantation for float charging here https://www.batteryskills.com/what-is-battery-float-charging/

 

[Dark-Fx]

That might be one of the problems right there....
Lead/acid automotive battery charging circuits generally run up to 14.6V and are limited to that max voltage by regulators built in the alternator. If Rivian is only charging their 12V AGM batts to 13.7 volts that's far too low and leaving lots of stored energy on the table resulting in a very low state of charge even when "full".
The Rivian 12V battery even shows recharge voltage (14.1-14.7V) right on the side of the battery...

The OP didn't give the whole story about the battery charging circuits because they didn't observe it long enough. Rivian likely has periodic higher voltage sessions to better maintain the battery, but typically you want to leave it the voltage in the float area when not charging or discharging, which is where 13.7V is.

 

[Riviot]

Customer Service told me that. If I put in an a battery on my own, and anything happened after that and they traced back to the battery, it would not be covered. As you can tell there is a huge flaw in how the batteries work. So next time something happens, what do you think they will say?

Option 1: Jumper a backup to both batteries through the frunk

Option 2: Replace the batteries and keep the originals. If/when issues return, or you get back home, put the trash batteries back in.

 

[DannyC]

At this point the best answer from Rivian is that the truck is not "sleeping" enough. Since I run my inverter a lot the 12v system does not maintain the batteries all the time and typically does that while sleeping. Also I received my truck in March and have a lot more miles than most. Hopefully newer software will prevent this from happening again. Older software may have damaged the batteries and finally it just failed.

Quite stupid that the truck needs to "sleep" to maintain itself, there should be a better way to do that in the software. If its a hardware limitation then hopefully version 2 of the R1T/S alleviates these issues.

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