12v Lead Acid Battery Replacement

[mudito]

Not sure if this answers your question, or just provides a data-point. When my 12v dual batteries were critical, I was told to keep it plugged into L1 (or L2, I suppose).

During the 48 hour wait for mobile service, I noticed the HV battery would drop 2-3%, then the L1 charger would kick in and bring the truck back to my preset threshold. It did this probably 5-6 times over the few days while waiting for mobile service. I assume the HV drop in capacity was because the big battery was always trying to recharge the quickly dying 12v batts. Then, as the HV dropped a bit, the charger would kick in and bring everything back to my % threshold.

This is correct, and is my understanding that, If not plugged in, after a certain amount of repeated charging from the HV to the 12V, the computer will shut everything down to protect the HV battery from draining/dying.

If you ask me, I would have added some more logic to it. My 12V died with a 69% HV SoC. I would have it programed like "48hrs on this mode or HV drop below 15%, then shutoff"... That would have alerted me with enough time to keep the truck plugged in and avoid a brick

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[ndmiller]

Based on all the stories and data points, seems like something goes awry with the 12V that stops the charging process from HV and the 12V completely drains.

We also know Rivian has reached out to owners preliminarily to schedule 12V replacement, so sometimes the issue is seen in their telemetry from the vehicle. My guess is the overnight drains aren't seen as everyone is asleep at Rivian and if they see the issue during the US daylight hours they contact the owner.

An Odyssey, NorthStar, Panasonic in the same group as the Rivian would be better, but EV 12V batteries are in a very high use high stress environment (nothing on a pully like an ICE vehicle). Normal 12V in ICE die in a few years in very hot and vey cold US climates, so I would expect in an EV to have a shorter life.

I'm sure Rivian is trying to figure it out, and maybe they got a bad batch of batteries who knows.

 

[Singletracker]

Daniel - Actually, I was really wondering if anything was happening, with relation to the HV battery, when the vehicle is plugged in, but NOT in a scheduled charging situation. I understand what you are saying regarding keeping the HV battery at a set percentage of charge.

 

[mudito]

Daniel - Actually, I was really wondering if anything was happening, with relation to the HV battery, when the vehicle is plugged in, but NOT in a scheduled charging situation. I understand what you are saying regarding keeping the HV battery at a set percentage of charge.

I'm assuming that if battery drops below certain % under the charge limit with a dying 12v,It can override the scheduled time of charge?? Just throwing theories ?

 

[Singletracker]

I was hoping that, when plugged in, the vehicle could determine when to suck some juice, depending on certain system needs. However, just plugging it in may not do anything, if it’s not part of a specific charging schedule. Dunno.

 

[SparkyR1t]

If it's not covered under warranty I would diy it with aftermarket. Rivian charges about $700 for it and we all know these don't last long.

I seem to recall a federal law from times past that says something to the effect if a vehicle manufacturer refuses sell you the part and won’t supply technical repair ( may be at a cost) info they must make those repairs at their cost.

 

[Nixapatfan]

I seem to recall a federal law from times past that says something to the effect if a vehicle manufacturer refuses sell you the part and won’t supply technical repair ( may be at a cost) info they must make those repairs at their cost.

They will sell you the parts and will also sell you the labor to install it. Their labor rates are about average their parts costs are way overpriced.

 

[Der]

I woke up to the 12 volt battery replacement warning this am. Called SC and they scheduled a mobile service appt for 4 days from now. Guess I should feel lucky. I’ve had the truck for 7 months/11k miles so I’m assuming it’ll be under warranty. Fingers crossed.

 

[JPK]

FWIW I had the same battery warning light come on recently, and I have a similar wait for mobile service. We have family visiting from out of town so our driveway is a bit crowded this week. As a consequence I did leave the truck unplugged the other night and had no trouble the next morning. Just a single anecdotal data point but maybe useful anyway.

 

[Gee Bee]

Too small of battery, poor location
I was bricked for ten days

I have three other cars so no rental required

 

[mudito]

I was hoping that, when plugged in, the vehicle could determine when to suck some juice, depending on certain system needs. However, just plugging it in may not do anything, if it’s not part of a specific charging schedule. Dunno.

IF I had a 12V warning (when mine died, it died at the same time as I saw the warning), I would eliminate the schedule (I have it from 8pm to 6am since I have $0 electricity at that time-frame), and keep it plugged in with a charge limit of 70%.

I don't think the truck might automatically override the schedule to keep the HV batt safe.. I hope it does but I don't think it would

 

[NY_Rob]

If it's not covered under warranty I would diy it with aftermarket. Rivian charges about $700 for it and we all know these don't last long.

I believe the going rate is in the $800-$850 range now

 

[Meash20]

I do not understand why Rivian and other EV 12v batteries are not user replaceable. ICE vehicles also experience these 12v battery failures the difference is that you can go down the street to the parts store and get a new one to slap in. It seems like a major marketing failure for these vehicles to be perceived as "bricked" by a dead 12v. ICE vehicles are also bricked with a dead battery in many occasions, but the ability to replace them prevents the perception..

 

[NY_Rob]

Based on all the stories and data points, seems like something goes awry with the 12V that stops the charging process from HV and the 12V completely drains.

It almost seems like the vehicle is "wearing out" the tiny 18AH batts due to constant depleting and recharging because of all the telematics Rivian has uploading all the time. Lead-acid batteries are only good for so many discharge/recharge cycles before they can no longer hold a meaningful charge with any current behind it. That's my WAG for today

 

[NY_Rob]

I do not understand why Rivian and other EV 12v batteries are not user replaceable.

They are user replaceable, but they are uncommon in size and AH capacity vs legacy automotive 12V batts. You can source replacements online vs a short trip to the corner Auto Zone and you can manually pop the frunk and replace then in less then an hour. Certainly not as simple as with a legacy vehicle, but not really difficult either compared to other automotive repairs.

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