12v Lead Acid Battery Replacement

[mkhuffman]

I would say that there is a third reason. An owner may want to get more than two or three years out of those expensive 12V batteries. Using a trickle charger (especially one with a desulphation process) will give you a better chance of extending the life significantly.
If this were a just a hundred dollar battery that an owner could pick up at at any Costco or auto parts store... and if this didn't involve the risk of one's Rivian failing to respond (and requiring extraordinary measures to open up - perhaps even being towed to a SC), I would say that reason #3 wouldn't be worth the effort.
But it is an expensive battery(ies) - the SC just quoted me $900 to replace batteries on a less than 2.5 year old truck, which does get driven quite a bit, and is on a L2 charger quite a bit in between. And the risk of the 12V batteries dying suddenly, leaving an owner and/or his family stranded, is very real.
But each owner has to evaluate the risk/reward/effort/expense trade off.

It sounds like you have a dual battery truck. The single battery ones will be much cheaper, and it is probably a DIY effort for me. I think it is under the passenger seat, but I have not taken the time to figure out how hard it is to replace. My guess is it isn't that hard.

I would replace the battery at the three year point regardless. Unless it is always trickling, it will not improve life expectancy significantly. I guess some people can keep it on one every time they park, but my truck is often not parked at home so for a large percentage of the time it would not be trickling.

And then there is the hassle of connecting and disconnecting the charger, which I would not enjoy. If the truck needed to sit for a month in my garage I would consider doing it.

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[zymolysis]

I would replace the battery at the three year point regardless. Unless it is always trickling, it will not improve life expectancy significantly.

I think you are assuming facts not in evidence.
The forum posts that I saw indicated that even intermittently trickle charging (once or twice a week, IIRC) would cause their Rivian to sleep much longer, in some case (at least) all through the night, instead of waking up every few hours to recharge the 12V battery. I would say that alone is evidence of a healthier battery; and it also shows that it has reduced the number of charge cycles during a given period of time. It isn't conclusive, but it seems to me that occasionally connecting a battery tender (or equivalent) could have substantial benefit, extending the life of the battery (improving your odds of actually getting to three years), as well as reducing vampire drain.

 

[mkhuffman]

I think you are assuming facts not in evidence.
The forum posts that I saw indicated that even intermittently trickle charging (once or twice a week, IIRC) would cause their Rivian to sleep much longer, in some case (at least) all through the night, instead of waking up every few hours to recharge the 12V battery. I would say that alone is evidence of a healthier battery; and it also shows that it has reduced the number of charge cycles during a given period of time. It isn't conclusive, but it seems to me that occasionally connecting a battery tender (or equivalent) could have substantial benefit, extending the life of the battery (improving your odds of actually getting to three years), as well as reducing vampire drain.

It could be that those trucks are not being driven enough to fully charge the LVB, and using a tender fully charges the LVB and keeps it there as long as it is connected. So it could make a difference in that situation, so I agree. But if I keep my R1 for more than three years, I will change the battery at the 3 year mark, even if you talk me into connecting it to a tender when at home.

My Mach-e was the same way. It didn't have a vampire drain issue, but the Mach-e does fire up the HVB to charge the LVB somewhere below 50% SoC. I measured it on my car.

And many Mach-e owners have seen failures around the 3 year mark. It wears out from all the charging and discharging, and if not driven, the LVB spends a lot of time at a lower than healthy SoC. I proactively replaced the battery at 3 years in that car also. It is a minor expense that prevents potential stranding.

 

[JacobAZ]

I think this is all true.

IMO there are two reasons to use a trickle charger to maintain the LVB:
1. You are not happy with the vampire drain and want to reduce drain of the HVB.
2. You don't drive the truck very often, so it sits for long periods of time, resulting in LVB drain and repeated charging cycles (from HVB or L2). This is similar to what happens to an ICEV when it is not driven very often. It sits, and consequently it does not go through the charging process that happens when driving. While the R1 will charge the LVB when parked and "off", it gets charged the entire time it is driven (until it is fully charged, of course). So lack of driving means less full LVB charging. Same as ICEVs.

Anyone who uses their Rivian for a daily commuter is likely getting enough charging time on the LVB to keep it healthy. Of course, short 1 mile drives are not good enough, even for ICEVs. If the truck sits for days, is driven for five minutes, and then sits for days, it is probably a good idea to trickle charge the LVB.

If you are in the middle, like I am, not doing daily commutes but driving it frequently, I wouldn't worry about the LVB. The truck is designed so that most people don't need to do exceptional maintenance to the LVB. Those who rarely drive, however, should think about hooking up a trickle charger.

Good explanation, but a few explanations/corrections ...

One charging cycle is 100% to 0% to 100% SOC. It's based upon how much you charge/discharge not frequency. If you charge 2 times 50%, or 5 times 20%, both are a cycle. More small charges is no worse than fewer large charges.

The LVB does not care what the charging source is. Trickle charge or HVB its all just electrons from LVB perspective. Neither is better than the other as for the health of the LVB. L2 only charges HVB.

Trickle chargers - a basic trickle charger puts out a very low current and probably will not be able to keep up with what the R1 is using when sleeping but will definitely slow down the drain and is contributing to a cycle of the LVB. However, smart trickle chargers have the ability to periodically measure the battery voltage and ramp up the current to charge the battery to 100% SOC ... similar to the R1 BMS.

Lead acid battery's loose voltage at they are used, Charging restores the voltage in a good battery. The R1 BMS either monitors this (like a smart trickle charger) or monitors the amount of current used while sleeping (not sure which method Rivian uses). When a threshold is reached the BMS tells the HVB to charge the LVB to 12 volts/100% SOC. You can see on the energy display screen when this occurs. On my Gen 2 it varies from about 6 hour to 24 hour interval. Depends on what the R1 is doing when it sleeps (that's another topic).

Bottom line, if working properly the BMS will keep the LVB well charged, same as a trickle charger. Adding a trickle charger has two benefits, 1) act as a backup to the R1 BMS for the LVB 2) over a long period of time slightly reduce cycles of the HVB. It would have no effect on the heath of the LVB.

 

[JacobAZ]

I think you are assuming facts not in evidence.
The forum posts that I saw indicated that even intermittently trickle charging (once or twice a week, IIRC) would cause their Rivian to sleep much longer, in some case (at least) all through the night, instead of waking up every few hours to recharge the 12V battery. I would say that alone is evidence of a healthier battery; and it also shows that it has reduced the number of charge cycles during a given period of time. It isn't conclusive, but it seems to me that occasionally connecting a battery tender (or equivalent) could have substantial benefit, extending the life of the battery (improving your odds of actually getting to three years), as well as reducing vampire drain.

You are correct that the trickle charge increases the time interval for the HVB to wake up and charge the LVB. However, this does nothing for the health of the LVB. See explanation of cycle in prior post above (cycle is 100 to 0 to 100). The LVB only knows it is receiving electrons, not the source and the contribution to a cycle is the same.

 

[mkhuffman]

Good explanation, but a few explanations/corrections ...

One charging cycle is 100% to 0% to 100% SOC. It's based upon how much you charge/discharge not frequency. If you charge 2 times 50%, or 5 times 20%, both are a cycle. More small charges is no worse than fewer large charges.

The LVB does not care what the charging source is. Trickle charge or HVB its all just electrons from LVB perspective. Neither is better than the other as for the health of the LVB. L2 only charges HVB.

Trickle chargers - a basic trickle charger puts out a very low current and probably will not be able to keep up with what the R1 is using when sleeping but will definitely slow down the drain and is contributing to a cycle of the LVB. However, smart trickle chargers have the ability to periodically measure the battery voltage and ramp up the current to charge the battery to 100% SOC ... similar to the R1 BMS.

Lead acid battery's loose voltage at they are used, Charging restores the voltage in a good battery. The R1 BMS either monitors this (like a smart trickle charger) or monitors the amount of current used while sleeping (not sure which method Rivian uses). When a threshold is reached the BMS tells the HVB to charge the LVB to 12 volts/100% SOC. You can see on the energy display screen when this occurs. On my Gen 2 it varies from about 6 hour to 24 hour interval. Depends on what the R1 is doing when it sleeps (that's another topic).

Bottom line, if working properly the BMS will keep the LVB well charged, same as a trickle charger. Adding a trickle charger has two benefits, 1) act as a backup to the R1 BMS for the LVB 2) over a long period of time slightly reduce cycles of the HVB. It would have no effect on the heath of the LVB.

I agree with what you posted about charging cycles. But a AGM battery (unlike a lithium battery) has a higher rate of sulfation at lower SoC levels, so the more you can keep it at 100%, or close to 100%, the longer it will last.

An external charger that is always charging the LVB, even when the truck is sleeping, will decrease the time the battery spends at lower SoCs, reducing the rate of sulfation and increasing battery life. It isn't just the cycles that wear out the battery, it is how long it spends at lower SoCs that also matter.

If your truck sits for long periods with only very short drives, the AGM LVB will not be at 100% very often, and sulfation will be higher when compared to those who drive longer and more often. In that case, a trickle charger is a good idea. I don't think it is necessary if you are driving enough to keep the LVB at a high SoC on a regular basis.

I do think an annual desulfation of the LVB is a good idea. I did that with my Mach-e. When I did it, the battery seemed to be in pretty good shape. Regardless I still replaced it at the 3 year mark.

I can share the desulfation procedure if anyone is interested. I will likely do it to my Rivian. I do it to my ICEVs also.

 

[JacobAZ]

An external charger that is always charging the LVB, even when the truck is sleeping, will decrease the time the battery spends at lower SoCs, reducing the rate of sulfation and increasing battery life. It isn't just the cycles that wear out the battery, it is how long it spends at lower SoCs that also matter.

If your truck sits for long periods with only very short drives, the AGM LVB will not be at 100% very often, and sulfation will be higher when compared to those who drive longer and more often. In that case, a trickle charger is a good idea. I don't think it is necessary if you are driving enough to keep the LVB at a high SoC on a regular basis.

my ICEVs also.

Good point on sulfation. It's my understanding that the Gen 2 has a large capacitor along with the LV battery. The BMS on my gen 2 appears to do a good job of regularly charging the battery/capacitor when parked (multiple times in 24 hours). In between charges, the capacitor, if of sufficient size, should act as a trickle charger keeping the battery at 100%. Has anyone verified if this is correct?

 

[mkhuffman]

Good point on sulfation. It's my understanding that the Gen 2 has a large capacitor along with the LV battery. The BMS on my gen 2 appears to do a good job of regularly charging the battery/capacitor when parked (multiple times in 24 hours). In between charges, the capacitor, if of sufficient size, should act as a trickle charger keeping the battery at 100%. Has anyone verified if this is correct?

Maybe I will try to hook up a battery meter to gather some data about this. But if the truck is waking to charge the LVB, it is likely much lower than 100% at that point. Otherwise, why wake to charge? It will be stupid to wake the truck if it is still above 90%, IMO. Or even 80%.

 

[zymolysis]

if the truck is waking to charge the LVB, it is likely much lower than 100% at that point.

Exactly.
The more time the battery spends at the lower charge levels, and the more charge cycles from low charge back up to acceptable charge, the worse the health or battery life will be. To just depend on the Rivian waking up (when the 12V battery is low on charge) to recharge the battery won't give the longest life for the 12V battery. A good trickle charger should keep the battery at optimum levels during that time, not at some point between acceptable and perilously low charge. I should think that much would be obvious to the members of this forum.
And the results, as detailed in other conversations (here in the forums) indicate that battery health improved with intermittent use of a battery tender (or equivalent) - the owner's Rivian slept longer, as I recall, even when the battery tender wasn't hooked up - which means the 12V battery wasn't discharging as quickly as it had, before use of a battery tender. And that indicates that the battery's capacity had improved from what it had been before use of the battery tender.
Sure Rivian recommends keeping it plugged into an L2 charger, after there has been a 12V battery error. They aren't going to tell you to connect battery tenders to the battery (batteries). The L2 charger and Rivian waking up to charge the 12V battery *might* get you through until the SC can replace your 12V battery. But connecting it to a battery tender is more likely to extend the life of the 12V battery, and will give a better chance to keep the 12V battery alive, until it can be replaced.

 

[antimatter]

Let me ask a quick question - as far as installing the lead for a trickle charger, is there any issue with the 12-volt battery being disconnected for a minute or two? I have a bunch of basic chargers from my years of motorcycle riding that I can use. I'll just need to disconnect the battery for a bit.

 

[mudito]

Let me ask a quick question - as far as installing the lead for a trickle charger, is there any issue with the 12-volt battery being disconnected for a minute or two? I have a bunch of basic chargers from my years of motorcycle riding that I can use. I'll just need to disconnect the battery for a bit.

I did it in my Dual Battery Gen1 without disconnecting anything . Check my post here: https://www.rivianforums.com/forum/threads/trick-for-maintaining-health-of-the-12v-battery.37720/ where I link where I got the idea from and @NY_Rob had pictures of it

 

[SwampNut]

I've had two replacements.

 

[IGR]

That’s funny, just got same message this morning.
My battery was proactively replaced by Rivian just this past October.

11 months life span on a 12v battery is concerning to be honest.

 

[SwampNut]

Mine was replaced at the end of April. And my truck is now sitting at twraps’ place 700 miles away.

 

[mudito]

That’s funny, just got same message this morning.
My battery was proactively replaced by Rivian just this past October.

11 months life span on a 12v battery is concerning to be honest.

Interesting indeed. Is it a Dual battery or a Single one?
How often do you L2 charge at home? Daily? Weekly?

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