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Low SOC when pulling into a 150 kw question.

Low SOC when pulling into a 150 kw question.

So I'm in the middle of an 1800 mile mini vacation and ran into an issue at a SC Friday that had me scratching my head.

With the exception of one SC stop in Martinsburg WV the other four 150kw stops have been faster than I can wander into the Sheetz/Wawa/Starbucks to get a snack.

The only difference with Martinsburg was I decided to push one SC past Hagerstown (120kw) letting my SOC drop below 5%. The rest have been in the 15-20% SOC range.

While the Martinsburg rate initial peaked above 100kw, it quickly crashed down into the 30kw and slowly inches into the 50kw range and only much later in the season got much above that.

I realize such a low SOC places higher load on the battery generating more heat, and it was hot out. So, do people think that was the more likely throttled due to an overly warmed battery, or did I pull up to a bum charger? Thoughts?

Thinking of charging my behavior a little on the return leg to keep the SOC in the 20+ zone to prevent another SC thermal (if it was) delay.

kevin_rf | July 14, 2019

Btw. Started in the Central MA area with 95% SOC.
Charged in:
Parsippany NJ
Martinsburg WV
Lexington VA
Made a weekend dash into Renick WV
Charleston WV
Dayton OH.

Almost no one at any of the SC's. Did see some icing, but not too bad.
Will be heading back to Central MA through Cannonsburgh PA. SC stops yet to be determined. Currently a bit under 80% SOC with century mode on.

vmulla | July 14, 2019

Did you notice any messages about Pre-conditioning the battery as you approached the SC?
I'm pretty sure you saw that message as you approached Hagerstown. What happened after you passed Hagerstown?

BTW I spent 4 years in that area. Thanks for a trip down memory lane.

kevin_rf | July 15, 2019

Forgot about the preconditioning, made a stop at the Hagerstown Walmart and then pushed the extra few miles to Martinsburg.

I know I was debating (changing on the nav) a couple of different SC's when I made the split second decision on the Parsippany SC since it looked like the Allentown SC would be a close shave. That didn't seem to impact charging speed. Though, the car did sit a little during the Walmart run in Hagerstown before pushing another 20 miles down the road.

Bighorn | July 15, 2019
Hp.1193 | July 15, 2019

Were there others charging on either side of you ?

jjgunn | July 15, 2019

That's interesting @Bighorn. Didn't know that.

I read that one guy ran the car down to 2% then used the 250 kW V3 in Fremont. He didn't seem to have any issue on that test. Maybe the v3's differ from the 150 kW v2?

I've seen this happen at a couple SuCh'r stations. Every time I've experienced it, it's the electric feed to the station. Nothing wrong with your car. Had the same thing happen at Foster City w/SoC at 17% -- Moved to Hillsdale & an unpaired charger ramped up to 142 kW with no issue.

jjgunn | July 15, 2019

1 more thing....I usually use the Urban SuperCharger (72 kW) the charge seems to stay more consistent longer and IMO is better for long term battery health.

hokiegir1 | July 15, 2019

I second @HP's question -- that almost sounds like it was a shared pair, at least as a contributing factor. Also, the "partner" is not always right next to the pedestal. You have to look at setup.

Some are:

1A - 1B - 2A - 2B - 3A - 3B

And some are:

1A - 2A - 3A - 1B - 2B - 3B

You want to avoid a shared number if you have a choice, as it reduces both people's speed.

Hp.1193 | July 15, 2019

Correct ^

Bighorn | July 15, 2019

I suspect v3 and v2 will operate differently. I don’t think he’d have seen an early 100 kW delivery on a shared pair.

Hp.1193 | July 15, 2019

That's also true. Also no need to have precondition if your on road trips, the long driving is the "preconditioning"

hokiegir1 | July 15, 2019

@Bighorn -- I missed that it hit 100kw before dropping to 30.

Bighorn | July 15, 2019

Eau Claire is even more confusing. It’s 1B2B3B1A2A3A. Try explaining why you pulled in next to a know-it-all who is pissed because you didn’t leave a space between you and him.

Hp.1193 | July 15, 2019

If you weren't sharing a stall, in this case you may not have, it was prob a faulty charger since you had success at other SCs during your trip.

Bighorn | July 15, 2019

I hadn’t heard confirmation that Fremont was operating to full capacity yet. I know the stalls were limited the first few weeks and that the cars needed new firmware. Has anyone seen 250 kW there yet?

jjgunn | July 15, 2019
hokiegir1 | July 15, 2019

@Bighorn - Atlantic Station (in ATL) has 2 rows that are perpendicular to each other...so the As are on one arm of the T and the Bs are on the other. People constantly saying "I'm not sharing and getting low speed!" when they actually are and just didn't see the rest of the chargers.

charles.a.braun | July 15, 2019

Bighorn | July 15, 2019
Eau Claire is even more confusing. It’s 1B2B3B1A2A3A. Try explaining why you pulled in next to a know-it-all who is pissed because you didn’t leave a space between you and him.

=====

Especially when you are in a Model 3, and that "know it all" is looking down his/her nose at you from their Model X.

vmulla | July 15, 2019

The most plausible explanation is what @bighorn said - shared stalls

I have a theory that would explain fast charging for a short while followed by slower charging.
I believe that pre-conditioning the battery is about making as many individual cells in the battery pack achieve a SOC that accepts faster charging - instead of having uniform drain within the battery, more cells at ideal charge SOC would be able to soak up the charge faster. That's the premise.

When the OP approached the intended stop, his car would have been at that ideal state - maximum cells at ideal SOC for charging. After he passed the intended SC stop, the car would have drawn power from cells that are at a decent capacity - but not the cells that would are at ideal charge SOC (sorry I don't know how to better describe this)

As the car comes closer to next SC, the car is running low on charge anyway, and as a way to optimize the charge speed, the car draws power from cells that are already at good SOC while maintaining BETTER charging SOC for another set of cells.

(Damn, sorry it's coming across as gibberish to me as well, but I think I'm onto something)

At the SC, there are a few cells at the right SOC - so the car charges rapidly. Once those few cells are over 70% SOC, then most of the car's cells are going down to a slower charge speed. Eventually, the charge curve follows the familiar pattern.

Two things -
1. I believe the OP enjoyed faster overall charging despite the variances in charge speed
2. I believe this occurred because OP did not stop at the intended SC where the car was prepped for faster charging.

whew!! :) ..and thank you, I like these kinds of mysteries - just theoretical talk based on experiences and not real knowledge, but exercises the mind all the same :)

Bighorn | July 15, 2019

@jj
Thanks for the link!

@charles
Did we just have that conversation or did I have that exact same exchange with someone else this week.

@vmulla
I’m not suggesting sharing being the culprit, but speculating that it’s a normal ramp up with low SOC. It is seen with some battery iterations on the Model S Both if my car’s start out at max power, but I know of others that do not when arriving with very low SOCs. And preconditioning has never been a necessary adjunct for me to see maximal power immersion arrival. Battery cooling may be helpful in very hot environments, but supercharging will quickly raise the battery temperature leading to slower charging, though it can be a function of a hot supercharger throttling power as well.

Bighorn | July 15, 2019

Immersion/immediately upon

vmulla | July 15, 2019

@bighorn,
Got it!

@bighorn,@charles,
Yup, you had that discussion on the forum a few days ago.

Bighorn | July 15, 2019

@vmulla
Thanks—I’m 40 days on the road as of today and a lot blends together:)

vmulla | July 15, 2019

@bighorn,
Curiosity is killing me here. What do you do? You mentioned physician in one of the threads, but why are you on the road so much? And all the freaking Superchargers in the far flung areas need a physician? And how do you keep them all memorized? Many times I don't recollect the Supercharger until I'm pulling into it, everything seems familiar but I need to rediscover :(

Bighorn | July 15, 2019

@vmulla
I retired a year ago. Before that, I was carving 2 and 3 week breaks out at work This time, I was mostly visiting family and friends on the east coast, but visiting all the superchargers I haven’t been to, in my spare time. We have a huge database of all the people competing to visit superchargers. No way I could remember the 740 chargers I’ve been to, but I’ve been to many numerous times in the process.

kevin_rf | July 15, 2019

Finally finished today's activities and can reply. Had another 144kw session that went faster than I can down a burger in Cambridge OH.

Martinsburg wasn't a pairing issue, unless wonder woman bought an invisible Tesla. No one was at the Martinsburg SC. Just a flukey session. Bighorn thanks for the link on the low SOC causing charging power issues. Think I'm going to try harder to stay above 15/20%.

On the final leg home by way of Sarris's candies in Cannonsburgh.