Odd BMS behavior

[2P168S]

When charging on Level 1 at low power levels (roughly one kW), I have noticed some odd behavior from the BMS. When I start driving, the car will report a certain SoC, for example 92%. Then, after driving for 10-15 minutes, the SoC reported will actually go up. The biggest increase I've seen is 4% (so to 96% in my example). But several times I have seen other smaller increases, around 1-2%.

Has anyone else seen this? And if so, why?
An acquaintance of mine suggested it may be a result of a more complex SoC estimation algorithm (beyond just voltage look up tables and coulomb counting) but I am wondering if anyone else knows.

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[RAHRCR]

Yes but nothing to do with the EVSE I suspect. Just a recalibration of the guess-o-meter to more favorable driving conditions.

 

[whitex]

This is probably because L1 is unable to heat the battery up. Driving warms the battery. The warmer the battery, the higher the estimate SoC (and range).

 

[2P168S]

Yes but nothing to do with the EVSE I suspect. Just a recalibration of the guess-o-meter to more favorable driving conditions.

I see this behavior with the SoC (as opposed to the range, so this is unrelated to the GoM).

 

[Tooney]

I'm assuming you are aware that Porsche TSBs discourage 110v AC charging of Taycans. Some readers may not be.

 

[tchavei]

I charged my Taycan at 45kW up to 94% the other day. After leaving the charging station, after about 2km it increased to 95%. Battery temperature actually had dropped after the charge session so probably something internally calculated the new charge level.

 

[Jayyvr890]

Almost certainly due to battery conditioning once you start driving.

Also porsche no longer recommends using level 1 to charge the taycan. It can deplete the 12V and you end up with a dead car with 100% soc lol

 

[2P168S]

I'm assuming you are aware that Porsche TSBs discourage 110v AC charging of Taycans. Some readers may not be.

Thanks, I didn’t know that actually.
I found this one, which states that if the L1 charging power is too low, the car won’t charge at all.
https://static.nhtsa.gov/odi/tsbs/2020/MC-10172087-0001.pdf

I don’t have this problem (car charges fine). Are there others I should be aware of?

 

[2P168S]

I charged my Taycan at 45kW up to 94% the other day. After leaving the charging station, after about 2km it increased to 95%. Battery temperature actually had dropped after the charge session so probably something internally calculated the new charge level.

Yep, this matches what I see

 

[2P168S]

Almost certainly due to battery conditioning once you start driving.

Also porsche no longer recommends using level 1 to charge the taycan. It can deplete the 12V and you end up with a dead car with 100% soc lol

I don’t follow. What battery conditioning once driving?

 

[Tooney]

Thanks, I didn’t know that actually.
I found this one, which states that if the L1 charging power is too low, the car won’t charge at all.
https://static.nhtsa.gov/odi/tsbs/2020/MC-10172087-0001.pdf

I don’t have this problem (car charges fine). Are there others I should be aware of?

That is a good one.
Here is another TSB indicating 110-120v AC charging should be used in emergencies only.
https://static.nhtsa.gov/odi/tsbs/2023/MC-10231403-0001.pdf

Porsche has issued a number of TSBs dealing with AC charging. Most are in response to problems with PMC+ and PMCC EVSEs. They repeatedly advise not using L1 charging for Taycans.

Best list of Taycan TSBs is the link provided by @rs38 and described here: https://www.taycanforum.com/forum/t...tis-extracted-from-nhtsa-updated-daily.12752/

 

[2P168S]

That is a good one.
Here is another TSB indicating 110-120v AC charging should be used in emergencies only.
https://static.nhtsa.gov/odi/tsbs/2023/MC-10231403-0001.pdf

Porsche has issued a number of TSBs dealing with AC charging. Most are in response to problems with PMC+ and PMCC EVSEs. They repeatedly advise not using L1 charging for Taycans.

Best list of Taycan TSBs is the link provided by @rs38 and described here: https://www.taycanforum.com/forum/t...tis-extracted-from-nhtsa-updated-daily.12752/

Thanks for sharing. Yes, I gave up on the PMCC after a few days. Using another EVSE I had laying around.

I will eventually be on L2, but moved into a new house and haven't got around to it yet.

 

[Jonathan S.]

Doncha just hate that guy who bumps an old thread?

So maybe this should be a new thread, but...
... what is the current consensus (if any) on L1 charging?

I'm not one of those guys (whom you hate even more) who plans to buy a Taycan yet won't spring for home L2 charging.
(Already have a Juice Box 48.)

But I have found L1 charging to be useful on our BMW i4 M50.
Observed charging rate seems to correspond to the 1.2 kW L1 max.
Out of ~9k miles, I've L1 charged something like 4x overnight and once for just 2 hrs.
None of those were emergency situations, yet eliminated the need for some DCFC stops.

Reading the various threads here, and the TSBs, plus this:

https://www.divegearexpress.com/taycan-charging​

... my understanding is that Porsche advises against L1 charging b/c:

1. Home circuitry might not be able to handle, but that's the same for L1 charging with any EV.
2. If below 8 amp then the charge might be so low and erratic that the 12v battery will discharge, a la the old days of leaving the lights on. (Anyone remember when you would see a car with the lights on, and you'd try to door to see if perhaps the driver had both forgotten to turn off the lights and lock the door so that you can pull a Good Samaritan act? I recall a successful combination of those two only once!)

The charger EVSE (I hope everyone appreciates that correction!) that comes with our BMW has a max L1 rate of 10 amps, so does that alleviate the second concern?
Or does every mobile EVSE support a L1 rate of at least 10 amps, and the problem instead is that home circuitry might drop below that, then drain the 12v battery?
(Awaking to a ~10% SoC boost has been nice, but awaking to a drained 12v battery would not be so nice!)

BTW (and apologies for the thread drift), the potential 4CT purchase is here:
https://www.infinitiofbellevue.com/...oss-turismo-4-awd-4d-wagon-wp0ba2y19nsa67077/
... with one problem being that I am not there, and more specifically almost at the other end of the width of the North American continent.
Link to the original window sticker in case anyone wants to weigh in:

 

[daveo4EV]

I believe L1 charging to be so anemic that it's truly only for "emergency" use - Porsche goes as far as to set a time limit of 12 hours in their latest written recommendations.

I think it's very very very easy for Taycan to consume more than 1.44 kW (the maximum "raw" power from a 120V/12 amp (15 amp breaker) circuit) - which means if the Taycan is consuming more than 1.44 kW you're actually losing ground while charging from a NEMA 5-15 circuit - I'm not saying this always happens, but it's possible if battery conditioning and other high demand electronics are enabled/turned-on while charging from a NEMA 5-15 outlet…

the only use case I personally engage in with L1 charging is battery overnight maintenance for example at a hotel - battery is at 98% after a fast charging session near my hotel and i want to wake up in the morning and find it still at 98% (or more) during a cold overnight - L1 charging as a maintenance activity makes the most sense to me - but not as a method to "gain" capacity in any meaningful way…similar approach for long term parking - say at a ski resort and there are NEMA 5-15/20 outlets in the underground parking for engine block heaters and I'm probably not driving the EV for a few days while I hit the slopes - having an EV plugged into "shore power" while away from home to make sure the battery has some power to tap is great for piece of mind - but I'd make sure to charge it via L2/fast charging before storing in the ski resort's garage for the week…

L1 in my mind is no different than a 12V battery trickle charger - if I'm going to be away from the vehicle (or overnight at a hotel) and I can plug into an L1 outlet - I shrug my shoulders and say "why not" - but it's for maintenance not capacity.

that's my $0.02 - YMMV

 

[Jonathan S.]

^ Interesting scenario for the overnight maintenance, thanks.

Curious though, for anyone who has plugged in at, say, more like 90% for that scenario, does the Taycan then reflect about 1%/hr SoC gain the next morning, or is it far less than that?

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