L2 charger down to 2.7kwh at 24F.. Should I be worried?

[mkhuffman]

It's a large, not large+. And throttling has affected me since I got the car in December.

It would be very interesting to see if a Gen2 Large+ has this issue.

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[MarkNorman]

@mkhuffman just like @OYLman, I have a Gen 2 Large pack and have had L2 throttling since I picked it up at the end of November. I don’t do a ton of long trips in the winter so pre-conditioning is a good enough work around for me, but I understand it’s still a hassle for some.

From what I’ve seen it is the the Gen 2 NMC packs (Large and Max) that experience throttling. Seems like the combo of the low-cobalt battery chemistry and heat pump is the issue. My understanding is the Gen 1 Max pack was the same chemistry but may be able to heat the pack enough with the PTC heater so it doesn’t throttle. Mostly rumor and conjecture but makes sense.

 

[COMtnEV]

I had a very long charge session yesterday where I did not experience throttling up to 95% SoC. ABRP battery temperature was around 58F at the critical 80% SoC. Rivian temp was 4-5F lower at start and end of session. This charge session was pretty similar to the one where ABRP temperature peaked at 54.7F and throttling occurred. Inspired by watching the preconditioning behavior on my first long road trip with multiple DCFC charging stops (another topic, but sadly unimpressed - took an extra 2 hours to cover the 600 miles compared to my Ioniq 5 - charging curves were awful, dropping to 60-70kW at ~40% SoC on Tesla, EA, and RAN chargers - not sure if I will use the Rivian to raod trip again - it's turning out to be a summer-time local play vehicle), I plotted up battery temperature data as a function of time and SoC for my post software upgrade charging sessions to try to understand what might be happening.

The plot of battery temperature as a function of SoC seems to be more systematic. The red line is yesterday's "successful" charging session. The dark blue line is the "unsuccessful" session. The data hints at a couple things:
1 - There appear to be differences in "heating rate" as a function of SoC. Heating seems to be faster between around 30 and 60% SoC, and then slows down.
2 - For some reason, the heating rate slowed significantly above 60% SoC in the unsuccessful charging session - the battery temperature actually fell as the charging session continued.
3 - The only differences between the successful and unsuccessful sessions are (a) starting battery temperature in the unsuccessful session was 2F colder, and (b) ambient temperature through the critical 30-70% SoC was about 8F colder for the unsuccessful charging session (even though the successful session started much colder). Ambient temperature had fallen to arbout 30F when the heating slowed in unsuccessful session.

I think the data suggests that the software is not telling the truck to "heat to X degrees", but rather that there is a set amount of power going into heating (if it is even that sophisticated), and that when the ambient temperature is colder, there is too much heat loss to allow the battery pack to hit whatever exact temperature is required to avoid throttling. This is different from how the battery preconditioning for L3 charging seems to work - the truck is pushing the heating to reach a specific temperature.

One other observation that I am at a loss to explain is that 45 minutes after I stopped charging, ABRP battery temperature had increased another 3.5F to 62.2F. This is much faster heating than at any time during the charging session - almost 7F/hr compared to a peak heating rate of 2F/hr during charging. Am curious if anyone has any thoughts. In the session with battery temps in the 60s, the battery pack temperature dropped 9F in the hour after charging stopped.

 

[MarkNorman]

@COMtnEV This is great data! Do you think this supports the theory that once a session has been throttled, the truck cannot recover from it? To state it another way: the session will be throttled unless the pack has reached appr 55F prior to 80%.

Re: the discrepancy between the temp shown on ABRP and the Rivian Drive Mode menu, my hunch is ABRP is reading max cell temp and the Rivian Drive Mode menu is giving minimum or maybe average cell temp. From using the CarScanner app on other EVs I’ve seen all of these variables and assume Rivian is monitoring them all as well.

I’ve had good luck with the ABRP team being responsive to feature requests. I may hit them up to plot out temp as a function of SoC.

 

[COMtnEV]

@COMtnEV This is great data! Do you think this supports the theory that once a session has been throttled, the truck cannot recover from it? To state it another way: the session will be throttled unless the pack has reached appr 55F prior to 80%.

Re: the discrepancy between the temp shown on ABRP and the Rivian Drive Mode menu, my hunch is ABRP is reading max cell temp and the Rivian Drive Mode menu is giving minimum or maybe average cell temp. From using the CarScanner app on other EVs I’ve seen all of these variables and assume Rivian is monitoring them all as well.

I’ve had good luck with the ABRP team being responsive to feature requests. I may hit them up to plot out temp as a function of SoC.

At this point, I would agree that once the truck throttles, it will probably continue to throttle. The only caveat being that if the battery pack is truly warming after charging stops (I am going to track that a little more carefully going forward - I've seen it at least once before), it might cross the magic threshold after 20-30 minutes, and then if you started charging, it wouldn't be throttled. at t

The other feature that would be really handy with ABRP (mostly for DCFC) would be to have the reading of what the charger is willing to output. I now know there's a way to use the "cheat codes" to access that info via the truck itself, but would prefer not to have to get into the service mode every time I charge. It would be a lot easier to have it instantly visible in the app so you could decide if it's the truck or the charger, and make an informed decision on what to do next. I really wish I had been able to check it on this road trip. Given the repeated rapid drop to 65-75kV charge rates after 30% SOC at multiple chargers, I assumed it was the truck. As a result, we started to drive Kyle Connor style, adding just enough charge to make it to the next DCFC charger, making a lot of stops (every ~100 miles). Except I added a little cushion, unlike Kyle. Not what I envisioned with a Max Pack.

 

[MarkNorman]

At this point, I would agree that once the truck throttles, it will probably continue to throttle. The only caveat being that if the battery pack is truly warming after charging stops (I am going to track that a little more carefully going forward - I've seen it at least once before), it might cross the magic threshold after 20-30 minutes, and then if you started charging, it wouldn't be throttled. at t

The other feature that would be really handy with ABRP (mostly for DCFC) would be to have the reading of what the charger is willing to output. I now know there's a way to use the "cheat codes" to access that info via the truck itself, but would prefer not to have to get into the service mode every time I charge. It would be a lot easier to have it instantly visible in the app so you could decide if it's the truck or the charger, and make an informed decision on what to do next. I really wish I had been able to check it on this road trip. Given the repeated rapid drop to 65-75kV charge rates after 30% SOC at multiple chargers, I assumed it was the truck. As a result, we started to drive Kyle Connor style, adding just enough charge to make it to the next DCFC charger, making a lot of stops (every ~100 miles). Except I added a little cushion, unlike Kyle. Not what I envisioned with a Max Pack.

Even if the heat transfer fluid stopped pumping at the end of the charge, some post-charge warming of the cells may continue but I would not expect the increase in warming rate that you observed.

I like your suggested ABRP feature better. If you don’t mind, I’ll submit it to them. I picture it as two additional info blocks under the charging plot for “requested rate” and “provided rate” or something to that effect.

I know it can be uncomfortable to begin with, but living at the bottom half of your pack is almost always the best way to roadtrip an EV, if time is a consideration. Two years ago our family did a 5500 mile loop across Canada and back across the US in a pair of Model 3s. By halfway across Canada we had learned the ‘splash and dash’ was the only way to go.

I’ve no doubt this will improve as the tech develops. We can see the future in the Chinese EVs and it’s a bright one.

 

[COMtnEV]

It's sad that we have to say "look at the future in China". Not a fan of their government, but having spent a chunk of time in the national security world, I have to say that there are advantages to a system that can focus resources on long-term priorities to gain a competitive advantage, rather than our highly inefficient (at best) light switch style on again, off again approach.

Charging strategy depends on the vehicle (and drive logistics). My Ioniq 5 pulls max rate (~220 kW) into the mid 50% SoC, and then drops into the 170-180kW range, maintaining that to around 75% SoC before dropping to "only" 120kW for the final couple minutes to 80%. Given the time it takes to pull off the road and initiate a charging session, it's significantly faster to stay and charge to 80%. I'm realizing I've gotten very spoiled by my <20 minute 15-80% charging sessions ! But from my limited DCFC experience with the R1T, it's pretty clear that splash and dash is the way to go, especially as the charging network continues to build out so there aren't as many areas I drive where I need to make a 200 mile or more jump.

 

[hobbyjogger71]

It would be very interesting to see if a Gen2 Large+ has this issue.

Sample size of exactly 1 vehicle, but my other friend with a Rivian has a G2 Large+ and does not experience throttling, or has not as of today. He's in a garage, but that seems hardly impactful based on the anecdotes shared here.

 

[mkhuffman]

Sample size of exactly 1 vehicle, but my other friend with a Rivian has a G2 Large+ and does not experience throttling, or has not as of today. He's in a garage, but that seems hardly impactful based on the anecdotes shared here.

The key is the battery temperature. If his garage gets cold and the battery temp drops below 55 or 50 F, that would be an applicable test. Can you check that out?

 

[portdirect]

The key is the battery temperature. If his garage gets cold and the battery temp drops below 55 or 50 F, that would be an applicable test. Can you check that out?

Based on everything - like you I'd be very surprised of a large+ hit this - as it's just a Max pack Limited to charge to ~77% of what a Max pack does. If the large+ has this behavior - we are effectively back to square one for all theories on what going on.

I was also looking through the docs Rivian sent to the EPA again for the 'fun with numbers' convo re the advertised range, and noticed that they do state both the nominal voltage and capacity for each battery in them:

Pack Size	Nominal Voltage	Charge Capacity	Calculated Nominal gross energy capacity	Consumer addressable energy capacity	Buffer
Max Pack	392V	382Ah	149.744kWh	140kWh	6.5%
Large Pack	406V	286Ah	116.116kWh	108.5kWh	6.6%

Though they actually look to have done the range test itself with a large+ pack, rather than a large. Based off this, I think I can put my tinfoil hat down - and say that unless they changed packs during the production run of gen2's - this phenomenon is unlikely to be down to reduced buffer. Odd that they wouldn't just answer the question when I asked what the gross capacity was and claimed it to be a trade secret.

 

[Rivian Roamer]

So, I finally got my R1T Tri Max and did some testing. It said out in 40F weather for 72 hours and got cold soaked. I upped the charge limit to 100 and watched it derate pretty aggressively. At 92% I took it for a very spirited drive for 9 miles. Watched it climb back to 92% at 11.2

 

[tbo42]

Just to add a data point here, I have a Gen2 R1S with Large battery, and a Tesla Wall Charger (@32 A, so about 7.4KW) with J1772 adapter. I hadn't previously charged past 75% or so, but when I tried today, I noticed charge slowed around 80% SOC down to ~4.5 kW. It then slightly recovered to 5.0 kW. Ambient air temp is 6°C, and the car was only driven briefly today (~4 km) so was probably close to that temp at start the start of charging. This is indeed much more aggressive de-rating than I saw on my old Tesla Model S, which would only slow down near 95% or so when AC charging.

I haven't yet tried DC fast charging with my Rivian, so not sure how it behaves fast charging

 

[Rivian Roamer]

I have word we may see some improvements in the next OTA.

 

[mkhuffman]

Just to add a data point here, I have a Gen2 R1S with Large battery, and a Tesla Wall Charger (@32 A, so about 7.4KW) with J1772 adapter. I hadn't previously charged past 75% or so, but when I tried today, I noticed charge slowed around 80% SOC down to ~4.5 kW. It then slightly recovered to 5.0 kW. Ambient air temp is 6°C, and the car was only driven briefly today (~4 km) so was probably close to that temp at start the start of charging. This is indeed much more aggressive de-rating than I saw on my old Tesla Model S, which would only slow down near 95% or so when AC charging.

I haven't yet tried DC fast charging with my Rivian, so not sure how it behaves fast charging

Well this pretty much confirms it isn't a Max Pack issue.

 

[Rivian Roamer]

Well this pretty much confirms it isn't a Max Pack issue.

Gen 2 Large is just a Max pack with fewer modules.

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