DC Throttling "battery conditioning"

[SeaGeo]

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.

Tesla was doing this before the heat pump. Rivian showed they are/can do this in a their cold weather testing video.

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[kurtlikevonnegut]

Is it crazy to think that they just are being very conservative with battery management until they get enough real world data from end users to make adjustments? Based on delivery volume, I don't think they have enough data yet to start making large scale changes but I do think that will change in the next 3-6 months.

 

[SeaGeo]

Is it crazy to think that they just are being very conservative with battery management until they get enough real world data from end users to make adjustments? Based on delivery volume, I don't think they have enough data yet to start making large scale changes but I do think that will change in the next 3-6 months.

It's possible, but it seems like it's more a refinement and addition of features (preconditioning) than it is intentional conservatism.

To me the conservatism is the ramp down curve at the end when the temps are good. Which is a reasonably conservative slope.

 

[Engi_Nerd]

Tesla was doing this before the heat pump. Rivian showed they are/can do this in a their cold weather testing video.

Agreed, I just meant that the efficiency gains of a HP aren't limited to cabin heating alone.

 

[lostpacket]

As another EV newb I am surprised this can happen in the middle of a DC fast charge. Intuitively I would have thought that just charging would generate enough heat to keep the battery warm at least enough to continue charging.

I guess if it's cold enough the normal heat generated by charging isnt enough to keep up with the heat loss to the outside air?

(Also thanks for putting those graphs together @SeaGeo !)

 

[SeaGeo]

As another EV newb I am surprised this can happen in the middle of a DC fast charge. Intuitively I would have thought that just charging would generate enough heat to keep the battery warm at least enough to continue charging.

I guess if it's cold enough the normal heat generated by charging isnt enough to keep up with the heat loss to the outside air?

(Also thanks for putting those graphs together @SeaGeo !)

It surprised me a bit as well. Kyle said that was happens (basically) is it's easy for the EV to take in current at relatively low states of charger, and then as the SOC increases it is more temperature sensitive. So it's not necessarily that the pack is cooling of while charging, but that it's approaching a low (or high) end of the temperature tolerance for a specific SOC.

Which tracks with what I've observed in my ID.4 in some cold environments as well. I'll plug in when it's in the 30s or 40s and despite pushing current through the pack it will frequently either not increase speeds up to the ideal curve, or it will actually slow down a bit as SOC progresses when it shouldn't. BUT in the summer I had super consistent charging sessions.

 

[slawwach]

I hope that those issues can be solved by software updates and do not require hardware changes.

Manufacturers do tweak charging curves, but is anyone aware of such a big change (simply looking at the average charging rate) that was accomplished by software update alone?

 

[bsaik]

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?

We have an EV. You basically got the gist of it. For road trips - You end up trying to start your trip with max charge and you want to work the lower end of the battery SOC so that you can charge quickly. When I'm on the road we never really charge past 80%.

So when charging on a trip, once the taper starts if you can comfortbly get to the next charge stop or destination, unplug and go. If you are heading to a charger and it looks like you might arrive there with more than enough charge (>15% or so) you can go faster with relatively little time penalty!

The other thing I had to wrap my head around is that in the middle of road trips your "useful" range is really about 60% of the full range of the pack, since you'll be working SOC from 10-20% or so to 70-80% most of the time. With our Tesla this usually works out to about 3 hours of driving between charges which is fine.

 

[SeaGeo]

I hope that those issues can be solved by software updates and do not require hardware changes.

Manufacturers do tweak charging curves, but is anyone aware of such a big change (simply looking at the average charging rate) that was accomplished by software update alone?

Same.

Yeah, so the EV6/Ioniq 5 don't currently have preconditioning, but the manufacturers have said that will be coming via an update. They have as bad or worse performance in the cold relative to what they "should" do than the R1T. Polestar pushed an update last fall that enabled preconditioning for DC fast charging based on your route, which is what I would expect Rivian to enable (I'd be fine with just a button to tbh). That's described here: https://insideevs.com/features/543641/polestar2-ota-update-preheating-battery/

Regarding the curve, here's an example. Despite my annoyance at VW for not pushing software updates to the U.S. in what's now.... almost a year, they did push a significant improvement to the charging curve for the ID.3 in europe. The upcoming update for the ID.4 has a marginal bump to the peak charging speed (125 to 135 kw) but the whole curve will also be bumped up and supposedly reduced a charge from 5 to 80% by 9 minutes, cutting it from 38 to 29 minutes. The R1T can't push the peak up much with regular CCS equipment at 400v, but they may be able to push it up between 60 and 85%. I'm much more concerned about getting a consistent curve out of it at this point though.

 

[Craigins]

so if it is the battery getting too cold, could it be issues with using the inverters for heat? Meaning, perhaps they can't use the inverter while DCFC.

but you'd think they'd have backup resistive heating that they could route the DC through to maintain the temp.

 

[SeaGeo]

so if it is the battery getting too cold, could it be issues with using the inverters for heat? Meaning, perhaps they can't use the inverter while DCFC.

but you'd think they'd have backup resistive heating that they could route the DC through to maintain the temp.

?‍

If I ever get a guide and truck and run into this I'll be sure to submit a "why is my truck charging like a Chevy Bolt" service ticket.

 

[Craigins]

?‍

If I ever get a guide and truck and run into this I'll be sure to submit a "why is my truck charging like a Chevy Bolt" service ticket.

pretty sure the Bolt's batteries were hot enough. ?

 

[Craigins]

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

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

alternatively, get a space heater on a skateboard.

Plug it into the 120v in the bed or gear tunnel and slide it under the truck while charging to keep it nice and toasty.

Maybe also get a truck cover to keep the warm air in. or for ease of use, just a truck skirt

It will be all the rage, I'm telling you!

 

[SeaGeo]

alternatively, get a space heater on a skateboard.

Plug it into the 120v in the bed or gear tunnel and slide it under the truck while charging to keep it nice and toasty.

Maybe also get a truck cover to keep the warm air in. or for ease of use, just a truck skirt

It will be all the rage, I'm telling you!

You need a front angle with the wipers for the headlights with the skirt.

 

[DB-EV]

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.



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.



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.

Thank you for the thoughtful and helpful response.

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