DC Throttling "battery conditioning"

[SeaGeo]

If ya'll haven't noticed, the wonky ass charging curve has been bothering me since @timesinks posted his first curve. Thankfully Kyle Connor livestreamed his trip back to Colorado from Phoenix. I went through and logged the curves from the latter half of the day, and it was very clear that battery conditioning was the cause of a couple of throttling events. Kyle was pretty convinced that it was because the battery wasn't warm enough, and was eventually coldgating. YMMV, but keep an eye out for the "battery conditioning" warning that is on the screenshot below. It shows up when it starts conditioning the battery mid-charge. It doesn't warn you ahead of time or anything, and it doesn't actually do much based on how little it recovered while charging. Until Rivian implements either manual or automated battery preconditioning, it looks like we may need to be doing some yo-yo driving to try and heat the battery up.

So, here are the curves. The dashed one are the ones that had conditioning occur during the session, and it happend right when the charging speed dropped off. For context, Kyle had been driving at highway speeds all day. The coldgate events were when the outdoor temperatures were in the 30s to low 40s as I understand it. One session that didn't coldgate he yo-yo'd beforehand (and actually got limited regen). The other instances were closer to phoenix and earlier in the day, so I assume warmer.

He unplugged the yellow curve too early to see it come back off peak, but the blue and orange curves seem to be a fairly reasonable ramp down in speed to 80%.

All of the curves were limited by the 350Amp issue with EA, so the max speed seen was about 155kw. He tried to charge at a station that apparently should have put out 500 amps per Ryan Huber, but that was one of the coldgate curves.

Hope this helps, and hopefully Rivian issues some more proactive battery temperature management to reduce the number of poor charging sessions like these. Even if it's just manual.

Sponsored

 

[Drterreur]

This is actually great. I prefer to stop more often (charge between 15-60%) than to have to wait for ever for one charge if preconditionning did not warm the battery enough on my model3 (slow agonising Kw ramp up).

 

[moosehead]

RJ mentioned a heat pump in forthcoming efforts during the 3/10 earnings call, but that did not seem to apply to the R1 gen. Is a retrofit or aftermarket HP possible?

 

[COdogman]

Has anyone gotten any confirmation from Rivian that this is a temporary situation and they will be addressing this issue via update? They have to be aware of it. This had to be happening on all of their test vehicles and employee trucks they had out in the world.

 

[DB-EV]

Thank you for this. For the newbie (me) can you explain coldgating, yo-yo driving, and battery conditioning?

Is it effectively that because the car was using energy during the charge to warm the battery, it could not draw?

One key use case in the winter is driving in the call about 250 miles one way. Does the current state of information suggest I should stop at 15% and charge to 50 and then hit the road? Thank you in advance.

 

[SeaGeo]

RJ mentioned a heat pump in forthcoming efforts during the 3/10 earnings call, but that did not seem to apply to the R1 gen. Is a retrofit or aftermarket HP possible?

You don't need a heat pump to warm the battery.

 

[Engi_Nerd]

I'm very much looking forward to Kyle's final impressions on how this truck does on road trips. I can justify adding 5-10 minutes to my current Model Y charging stops. I cannot justify adding 30+ minutes.

 

[SeaGeo]

Has anyone gotten any confirmation from Rivian that this is a temporary situation and they will be addressing this issue via update? They have to be aware of it. This had to be happening on all of their test vehicles and employee trucks they had out in the world.

I haven't heard official feedback to Kyle other than it currently doesn't precondition, nor have I heard of an owner asking their guide yet.

Thank you for this. For the newbie (me) can you explain coldgating, yo-yo driving, and battery conditioning?

Is it effectively that because the car was using energy during the charge to warm the battery, it could not draw?

One key use case in the winter is driving in the call about 250 miles one way. Does the current state of information suggest I should stop at 15% and charge to 50 and then hit the road? Thank you in advance.

So batteries like to be in a specific temp range when charging. Ideally its somewhere in the 25 to 35 celsius rsnge, but 15 degrees is also "ok" on the low end.

Coldgating is when the battery is colder than ideal, and it has to slow down charging to protect itself.

yo-yoing is basically just rapidly speeding up and slowing down to push and pull a bunch of energy through the pack to try and warm it up before getting to the charger.

Battery conditioning is just trying to get the battery in the ideal temperature range (typically). Either cooling or warming.

Preconditioning is doing that before getting to the charger.

And in most cases it looks like what you suggested would be pretty close to ideal for the R1T charging curve.

I'm very much looking forward to Kyle's final impressions on how this truck does on road trips. I can justify adding 5-10 minutes to my current Model Y charging stops. I cannot justify adding 30+ minutes.

Yeah, it's definitely got me a little concerned. He loves the truck, but he's definitely not impressed by the charging. I'm frankly pretty surprised how poor their thermal management prior to ordering charging seems to be currently.

 

[Riviot]

You don't need a heat pump to warm the battery.

Now, will a Solo stove fit in the frunk? ?

"It's not an engine fire, officer, I'm warming my battery!"

 

[moosehead]

You don't need a heat pump to warm the battery.

No, I get resistive heat and using waste heat, but in colder climates a HP sure would be welcomed efficiency both for cabin and battery conditioning. It has become both a standard and upgrade option on certain other EV’s, and certainly seems to help automatically precondition both heating and cooling in the Pcar and Audi lines.

Taycan Frank may chime in but presume that both the 800v architecture and the HP help the Taycan’s great charging curve and range efficiency.

Interested to hear Tesla owner’s experience as well, as they have had both recent HP additions and recall issues.

 

[SeaGeo]

No, I get resistive heat and using waste heat, but in colder climates a HP sure would be welcomed efficiency both for cabin and battery conditioning. It has become both a standard and upgrade option on certain other EV’s, and certainly seems to help automatically precondition both heating and cooling in the Pcar and Audi lines.

Taycan Frank may chime in but presume that both the 800v architecture and the HP help the Taycan’s great charging curve and range efficiency.

Interested to hear Tesla owner’s experience as well, as they have had both recent HP additions and recall issues.

A heat pump is more efficient, but that's a separate issue. It's also potentially problematic in very cold climates, hence Toyota had combined a heat pump and PTC heater in their EV. I'm not saying a heat pump wouldn't be beneficial (or not here), but a lot of people seem to think a heat pump is required to be able to precondition the battery.

The Taycan absolutely benefits from 800v. It's pretty disappointing to me that Rivian didn't implement at least an equivalent for charging. I personally wouldn't even bother with a max pack unless it charges st 800v.

 

[moosehead]

I also keep thinking about TRL’s Ike test, while we do not know battery temps, one would think the resistive heating potential would have been quite high after towing 8k lbs up 6k’ elevation despite 27F-35F ambient. Yet they experienced the same horrible battery throttling and charge stepdown at mid range SOC.

Like you, I sure hope Rivian can figure it out with internal programming of existing hardware. Winter driving is challenging enough without needing to yo-yo about.

 

[Gator42]

I'm very much looking forward to Kyle's final impressions on how this truck does on road trips. I can justify adding 5-10 minutes to my current Model Y charging stops. I cannot justify adding 30+ minutes.

For those of us without EVs can you share your charging strategy? Most of my knowledge has come from Kyle. Correct if I’m wrong but when working with the inconsistencies of the EA network he’s favored charging at max possible speed until the invitable taper, usually around 50 percent SoC, then back on the road, lather, rinse, repeat…

From SeaGeo’s graph, with one cold pack exception he still gets to 50 percent, so only one event interrupts that plan, yes?

 

[Gator42]

Taycan Frank may chime in but presume that both the 800v architecture and the HP help the Taycan’s great charging curve and range efficiency.

Do we factor in the BBQ Taycan ocean ecosystem into the equation? ?

 

[Engi_Nerd]

People get all twisted in knots about the heat pump operation in very cold temperatures. Ours has worked great down to single digits, but that's not the point. A heat pump allows you to very efficiently extract heat from both the environment and from your motors. This heat is then available not only for the cabin, but also to to condition the pack while operating in temperatures outside of optimal, which in the Northeast, is most of the time. Our Model Y runs roughly 380 wh/mi at 70 mph in 30-40 degree temps. If you're approaching a supercharger, it will run the motors inefficiently to generate a bit of waste heat, which the heat pump uses to warm the pack. We typically see efficiency of around 550 wh/mi during this preconditioning phase, which it will use for 10-20 minutes at a time.

@Gator42 Regarding Model Y road tripping, we get around 3 hours between stops in the summer and 2 hours in the winter, assuming starting with 90% SOC and pulling in with around 15%. Most charging sessions we've experienced have been around 30-35 minutes to get to 80% to continue the journey. It's possible to charge for less time by stopping more frequently, but I don't prefer this given that most SC locations are not on main thoroughfares. While I enjoy the slower pace of EV road tripping, I do find the last 10 minutes of charging starts to feel a bit annoying. A 20 minute charging stop would be pretty much perfect. A 60 minute charging session to hit 80% would feel like an eternity, particularly without onboard streaming capability.

Sponsored