Trick for Maintaining health of the 12V Battery

[mudito]

There are a few facts that I would like to state beforehand:

• It's known that 1-2% daily Vampire Drain (VD) loss in Rivian's (at least Gen1) is considered normal.
• It's known that most of that loss is attributed to 12V battery recharging (plus other losses that the Wake events generate when charging the 12v).
• It's also known and vastly tested that keeping a trickle charger on the 12V system, will virtually eliminate the VD (If I recall correctly, forum members tested ~30days with 1% or less loss in their HV battery).

Also worth knowing are the following background facts of my specific case:

• My vehicle is a dual-12V battery Gen1 QuadMotor R1T.
• My 12V battery(ies) died in mid-september. Replaced by Rivian under warranty.
• Never measured what the heck was going on with my 12V BEFORE this unfortunate event, so I don't have info from before-failure.

So, what I noticed AFTER I got new 12V Batteries is that, if left untouched/undisturbed (no Bluetooth-enabled phone around, GearGuard disabled at home, etc), my R1T would sleep anywhere between 8 to 14 hours straight without waking for (presumably) 12V charging. That holds true for every day between batteries being replaced until November 28th.

On Nov 25th, we flew off for (an extended) Thanksgiving vacation and we landed back at home on December 4th. After 11/28th I saw that the truck stopped sleeping for long cycles in lieu of brief charging sessions (as an average, 4-5hours sleeping with 60-90 mins of charging, give or take) ?

Frequent ~60mins wake/charge sessions:

After observing this behavior (and if you're curious, I lost 8% SoC in 9 and a half days of having my R1T parked at home and also as a fun fact, my wife's Tesla Model 3 lost 3.5% in the same period, same garage, same weather ), and after using my truck down to 30% SoC, I left it charging in my garage up to 80% at 40A instead of 48 one night (I normally do 70% but wanted a longer charge session) with the theory being that this session should top-off the 12V as well.

It did seem to "improve" the Wake/Sleep cycles but not that much, after that charging session, instead of being 4-5hrs to 60 mins, it shifted to ~6.5hrs for another 60 mins of charging.

Still intrigued if I would be able to go back to the original state, I grabbed my trickle charger (I have a currently disabled Focus RS with a blown engine waiting for parts sitting in my garage, and hooked to a 5A trickle charger, which I stole for this test), and connected it to the main (Driver's side) 12V battery for about 24hrs.

Now three straight nights after doing that, I'm seeing the following:

Conclusion:
We'll see how long it lasts until it starts doing shorter cycles again (sadly I'm going on a road-trip so it'll be hard to monitor for the next month but I won't trickle charge the 12V again, so I should still be able to get some info). But it seems to me that fully charging the main 12V battery somehow 'restored' its full capacity and it's being maintained above the "need to charge" threshold for longer periods. I would probably experiment doing an install like @NY_Rob did HERE so I can get both 12V "conditioned" maybe once a month or every other month in order to maintain the life of the prone-to-failure 12V Batts

Also, my theory is that the charging/discharging thresholds that Rivian uses might not be the best. If I assume the following:

• 100% = 12.6V
• 50% = 12.35
• 0% = 12.1V

What I'm guessing is happening is that Rivian is letting the 12V go down to less than 12.3V, but then charges up to (let's say) 12.45V. Then it will fall back to 12.3 faster and repeat the cycle. Now that I have manually fully charged the battery, it might never (or rarely) get below the 12.35V and when I plug in to charge the HV Battery, it has enough time to top-up the 12V battery up to 12.6V again.

I'm guessing something along those lines is going on. I know one of the members has a 12V monitoring system integrated with HomeAssistant. He might call out my theory and break it apart with data. (If you're reading this, feel free to do so!).

Anyway! Feel free to comment, and nerd out with me! This is just my personal observation on how my truck is behaving

Cheers!

Sponsored

 

[UnsungZero_OldTimeAdMan]

I wonder if Rivian could retrofit the dual 12V cars to single. And I wonder why they don’t use a higher capacity deep-cycle single 12V.

 

[mudito]

I wonder if Rivian could retrofit the dual 12V cars to single. And I wonder why they don’t use a higher capacity deep-cycle single 12V.

?‍ ... we all wonder lots of things ?

Me, personally, I wonder why don't attempt a different charging cycle for the 12V while the car is plugged in. Maybe there's a HW limitation on the Dc-to-Dc 12V charging module? who knows...

 

[BourboNole]

Where are you hooking up the trickle charger? Direct to batteries or the emergency taps in the rear? I have never once worried about vampire drain as I drive around 10 miles per day and never leave my truck unattended for long periods, but having had my 12v replaced back in November (thankfully for free), I would like to avoid a biennial $700 battery replacement going forward (that can't be done by me with a 10mm socket in 10 minutes). I have an old trickle charger I could hook up from time to time to top off the 12v if your theory of undercharging by the HV system holds.

 

[mudito]

Where are you hooking up the trickle charger? Direct to batteries or the emergency taps in the rear?

Directly to the main 12V battery. I cited a post (https://www.rivianforums.com/forum/...n-possibly-solved-or-hacked.31506/post-604664), look at that one. In my case, I didn't do both of them like NY_Rob did, but just the main (driver side) one.

 

[shap]

There are a few facts that I would like to state beforehand:

• It's known that 1-2% daily Vampire Drain (VD) loss in Rivian's (at least Gen1) is considered normal.
• It's known that most of that loss is attributed to 12V battery recharging (plus other losses that the Wake events generate when charging the 12v).
• It's also known and vastly tested that keeping a trickle charger on the 12V system, will virtually eliminate the VD (If I recall correctly, forum members tested ~30days with 1% or less loss in their HV battery).

Also worth knowing are the following background facts of my specific case:

• My vehicle is a dual-12V battery Gen1 QuadMotor R1T.
• My 12V battery(ies) died in mid-september. Replaced by Rivian under warranty.
• Never measured what the heck was going on with my 12V BEFORE this unfortunate event, so I don't have info from before-failure.

So, what I noticed AFTER I got new 12V Batteries is that, if left untouched/undisturbed (no Bluetooth-enabled phone around, GearGuard disabled at home, etc), my R1T would sleep anywhere between 8 to 14 hours straight without waking for (presumably) 12V charging. That holds true for every day between batteries being replaced until November 28th.

On Nov 25th, we flew off for (an extended) Thanksgiving vacation and we landed back at home on December 4th. After 11/28th I saw that the truck stopped sleeping for long cycles in lieu of brief charging sessions (as an average, 4-5hours sleeping with 60-90 mins of charging, give or take) ?

Frequent ~60mins wake/charge sessions:

After observing this behavior (and if you're curious, I lost 8% SoC in 9 and a half days of having my R1T parked at home and also as a fun fact, my wife's Tesla Model 3 lost 3.5% in the same period, same garage, same weather ), and after using my truck down to 30% SoC, I left it charging in my garage up to 80% at 40A instead of 48 one night (I normally do 70% but wanted a longer charge session) with the theory being that this session should top-off the 12V as well.

It did seem to "improve" the Wake/Sleep cycles but not that much, after that charging session, instead of being 4-5hrs to 60 mins, it shifted to ~6.5hrs for another 60 mins of charging.

Still intrigued if I would be able to go back to the original state, I grabbed my trickle charger (I have a currently disabled Focus RS with a blown engine waiting for parts sitting in my garage, and hooked to a 5A trickle charger, which I stole for this test), and connected it to the main (Driver's side) 12V battery for about 24hrs.

Now three straight nights after doing that, I'm seeing the following:

Conclusion:
We'll see how long it lasts until it starts doing shorter cycles again (sadly I'm going on a road-trip so it'll be hard to monitor for the next month but I won't trickle charge the 12V again, so I should still be able to get some info). But it seems to me that fully charging the main 12V battery somehow 'restored' its full capacity and it's being maintained above the "need to charge" threshold for longer periods. I would probably experiment doing an install like @NY_Rob did HERE so I can get both 12V "conditioned" maybe once a month or every other month in order to maintain the life of the prone-to-failure 12V Batts

Also, my theory is that the charging/discharging thresholds that Rivian uses might not be the best. If I assume the following:

• 100% = 12.6V
• 50% = 12.35
• 0% = 12.1V

What I'm guessing is happening is that Rivian is letting the 12V go down to less than 12.3V, but then charges up to (let's say) 12.45V. Then it will fall back to 12.3 faster and repeat the cycle. Now that I have manually fully charged the battery, it might never (or rarely) get below the 12.35V and when I plug in to charge the HV Battery, it has enough time to top-up the 12V battery up to 12.6V again.

I'm guessing something along those lines is going on. I know one of the members has a 12V monitoring system integrated with HomeAssistant. He might call out my theory and break it apart with data. (If you're reading this, feel free to do so!).

Anyway! Feel free to comment, and nerd out with me! This is just my personal observation on how my truck is behaving

Cheers!

Here is the voltage of 12V and thresholds when charging is kicking in:

 

[mudito]

Here is the voltage of 12V and thresholds when charging is kicking in:

Amazing! What I'm seeing there is that sometimes does 12.5, sometimes 12.6/12.7v... Interesting...

 

[NY_Rob]

I wonder if Rivian could retrofit the dual 12V cars to single. And I wonder why they don’t use a higher capacity deep-cycle single 12V.

Rivian had said they needed a certain amount of energy to run the 12V systems, but they couldn't find a single 12V battery that supplied said amount of energy and fit in the location where they wanted to locate it, so they decided to use two 12V batts which on paper solved the problem.

 

[shap]

Amazing! What I'm seeing there is that sometimes does 12.5, sometimes 12.6/12.7v... Interesting...

Something to add - when you start driving (even when it is 70 degrees outside) efficiency will be bad for about 5 minutes and then it will go up. After you stop for about 10 minutes, the same will happen when you start the drive. So it seems that the truck is doing something very power-hungry when it starts. This happens when the truck wakes up to charge the 12V battery. Here is why the Rivian fleet waste 150 Mega Watt PER DAY of energy!

 

[UnsungZero_OldTimeAdMan]

Rivian had said they needed a certain amount of energy to run the 12V systems, but they couldn't find or fit a single 12V battery that supplied that amount of energy, so they decided to use two 12V batts which on paper solved the problem.

But they went from dual to single. Mine is a single.

 

[mudito]

But they went from dual to single. Mine is a single.

Single + SuperCapacitor (assuming the capacitor supplies current during the surge demand of it).

 

[NY_Rob]

But they went from dual to single. Mine is a single.

Which means they only needed to account for startup surge drain and other momentary high drain events which the Super Cap addressed in single 12V batt models.

Even with the updated design, the 12V battery/system by far has been the most troublesome component in the R1 vehicles. I'm confident they've learned enough by now so the R2 won't have any of these nagging 12V battery issues.

 

[Erik+]

Sort of playing devils advocate here, so don't ridicule my postulation, or do, I won't be offended.

Say you consistently trickle charge your 12V at home, that maintains 12V battery health and theoretically prolongs battery life (compared to the HV system charging it per it set voltage drop cycles as noted above), and at least keeps any VD gremlins at bay. This would in turn would not trigger any auto notifications to the Rivian service master data center, assuming there is one, where it would trigger a notification that Rivian XYZ's 12V battery is showing signs of degradation and may require preemptive replacement. Then, assuming most people are only trickle charging at home when they are doing their basic daily driving routine, the 12V would never show any signs of potential failure since the owner is manually charging it to reasonable health whether that is daily, weekly, or on whatever set frequency. Then said owner takes an extended road trip where their trickle charging habits go by the wayside and the 12V system is left to fend for itself and only be recharged via the standard protocol. Said owner then may have a higher probability of experiencing a 12V failure because they have manually been charging up their 12V system regularly despite the possibility that the 12V may be nearing failure, so when the system defaults to not charging it until the voltage drops enough to indicate charging is needed, the 12V battery struggles to hold charge at that level and the internal charging system and or battery move into the failure state.

I experienced similar with my old jeep, which is obviously a much different system, but similar processes with manually keeping the battery on a tender and then when it needed to live on its own for some period of time with alternator only charging, the battery would struggle to hold its own charge via current only from the alternator.

 

[joesmith315]

Here is the voltage of 12V and thresholds when charging is kicking in:

Which HA sensor is reporting the 12v voltage? I'm using the following integration and I'm not seeing that sensor show up.

https://github.com/bretterer/home-assistant-rivian

 

[shap]

Which HA sensor is reporting the 12v voltage? I'm using the following integration and I'm not seeing that sensor show up.

https://github.com/bretterer/home-assistant-rivian

I have a separate Hardware sensor connected to 12v battery.

Sponsored