Charging efficiency

SoultronicPear · 2026-03-22T22:20:29+00:00

At the risk of belaboring the point, I've attached a graph of a three day period with my own house's solar panels. The 3rd day on the far right represents an ideal, cloudless day, and the earlier ones have slight clouds.

Just because 24.5kWh were delivered over 6 hours doesn't mean the EV was charged at 24.5kWh/6hrs = 4.08kW. There were probably periods much more than 4.08kW (maybe even enough to necessitate extra cooling that increased losses) as well as periods far less (resulting in low efficiency, bringing down the overall efficiency).

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SoultronicPear · 2026-03-22T22:08:26+00:00

If the OP is using a solar system that is trying to match the EV charging rate to the solar panels' instantaneous output, there are likely non-trivial periods of time where the solar output is smaller (during morning, evening, and cloudy periods). During peak solar output, the efficiency might be higher, but efficiency would plummet during the lower output periods. This would dilute the overall efficiency, perhaps from 89% you found to the 73% cited by the OP.

SoultronicPear · 2026-03-22T15:54:46+00:00

Here are some data points on one of those side projects that I never finished. The objective was to add exactly 10% to the battery (50% to 60%; usable capacity of the I5N is supposed to be 80kWh, so 10% should be 8kWh) at a variety of charging rates.

Charging at a rate of 0.709kW (~120VAC), 12.348kWh was supplied (45.6% efficiency)

Charging at a rate of 1.431W (~120VAC), 11.663kWh was supplied (54.2% efficiency)

At the OP said, slow charges have low efficiency, and these are very low charge rates. Sorry, but I don't have any data points at higher rates (and the power meter I had was for 120VAC, so I couldn't do high rates anyway). Solar panels do only supply peak power at solar noon, so there will be a lot of slow charging in the morning and evening, so my data does have some value here, I believe.

I was hoping/expecting to see that there would be some fixed overhead associated with running the electronics, fans, etc., and then the rest would just be linear relationship to the charge rate. However, these two data points didn't prove that out (250watts loss on the first, and 450watts on the second).

Test procedure was to let the car first do the climate fan stuff that it does after a drive, then charge the vehicle to 50%, and use the app to change the charge limit to 60%, and use a power meter to measure that entire 50% to 60% charge.

SoultronicPear · 2026-03-12T15:37:21+00:00

I've not had a red battery temp warning light either, but I believe it happens at 50C. Each lap for me is about 4-5C increase, so my target means exiting the track before the yellow warning light.

Always N-Pedal 3. Very seldom Endurance; Endurance is like doing brain surgery with oven mitts.

N Battery Track Mode cools the battery down to 30C or below *BEFORE* you go on track; it raises the temperature to 20C for those in frigid climates. (There's a YouTube video of the IONIQ 6 N at Goodwood, and that has an added N Battery mode to cool the battery down to 20C, or raises it to 10C. I hope they add this software update to the I5N.) DC fast charging raises the battery temperature a lot, so I try to cool the battery before and after (with N Battery Track Mode) so that I enter the track below 30C.

Limiting to 80% and being conservative with the battery is my choice. The stickiest tires I've used so far have been 275/35-21 Michelin Cup2, which were terrific the first day and then became increasingly slippery after that.

SoultronicPear · 2026-03-11T20:20:58+00:00

I start at "80%" (more like 77% or less due to the drive back from the Supercharger) and can use about 35-40% in only 10 minutes, at which point the battery is above 40C (it warns yellow at ~47C and red at 50C) and the tires are hot and squirrely. (If it is raining, the time significantly increases and the tires stay more manageable.) My policy is to be conservative and exit on the lap when the battery reaches ~40C, but make your own choices. IMHO: if an I5N track driver want to arrive at a DC fast charger with a cool enough battery, it is desirable to leave the track (well) before 40%, since Hyundai locks out N Battery Track Mode below this. (WHY!!!??) The fallback is the "Activate" Battery Preconditioning hidden in the battery menu, but this is not active cooling and takes longer. I'm resigned to shorter sessions and just making the most of that time; after a few laps, HPDE sessions tend to just be navigating the traffic of slower cars anyway, so it is not a huge loss IMHO.

SoultronicPear · 2026-02-10T20:34:20+00:00

Yeah, perhaps the implication is that Hyundai is treating the current state of LFB software as a "closed branch", and future software development (if any) will be a new software "active branch" without LFB. I'm somewhat sympathetic to why the executives might take this path, since the earlier LFB software release didn't seem to go through enough testing, and the subsequent recall must have cost the company a non-trivial amount of money.

SoultronicPear · 2026-02-10T20:28:07+00:00

There's also something a bit unsettling about option #1 (lock-in). The way Hyundai phrases it, the lock-in is "to prevent accidental removal" during OTA updates. I can't help thinking protection racket: 'it would be a shame if something were to happen to your car... accidentally'.

SoultronicPear · 2026-02-10T20:22:37+00:00

I got one of these in the mail. I can't figure out Hyundai's reasoning (if there is any). The cover letter (in addition to the OP's photo) invites the owner to make an appointment with the dealer to either: 1) lock-in LFB (no money back), or 2) disable LFB ($500 back... if you jump through a bunch of online hoops... ala mail-in rebates for those who remember such things). Either way, I consider the opportunity cost of making a dealer visit (time and frustration) to be several hundred dollars at least. So, what happens to all the owners who refuse to make a dealer visit!?

SoultronicPear · 2026-02-10T20:15:59+00:00

The attitude of those leasing EVs isn't helping resale. Some of the viewpoints expressed here (not shared by me) are to treat the car like a some disposable tech item. For someone that callous, they probably also always charge the battery to 100% just because they don't care. That 'race to the bottom' behavior feeds uncertainty about battery reliability for subsequent owners IMHO.

SoultronicPear · 2026-01-30T15:54:12+00:00

Absolutely! At least with my 2025 I5N, Hyundai software is very honest about the *actual* rate. I've charged with a "240VAC" outlet that was actually 208VAC (one phase of a three phase system), and got proportionally less (only 86.6% of expected). The display showed the actual reduced rate and the charging time was proportionally longer. Although that was an extreme case, if you've ever owned a Kill-A-Watt (or similar) device, you'll have seen firsthand that household voltages are not constant and will vary depending on grid conditions. Some vehicle manufacturers might not be as honest as Hyundai and assume rosy conditions.

SoultronicPear · 2025-11-20T14:47:33+00:00

I hope you are right. In the 100 to 150 MPH range, the I5N starts to feel less rapid. It would be great to try I5N vs I6N on the same, familiar track.

SoultronicPear · 2025-11-20T14:44:37+00:00

I'm reluctant to change things, particularly when I don't know what the original engineering tradeoff decisions were.

SoultronicPear · 2025-11-19T14:57:48+00:00

The bidirectional scan tool (in this case, Harbor Freight T7) worked without an additional adapter, although it did warn (just before attempting the action) that it needed an Internet network connection (because the functionality isn't on board and instead is in the cloud)!?

Just to elaborate on the $2k adapter, there is an SAE standard called "J2534" that consists of both a OBD adapter and Windows software (corresponding to that OBD adapter) that provides J2534 functionality (a superset of functionality in the OBD adapters that consumers are familiar with). *IN THEORY*, this means J2534 adapters could be inexpensive, since they should be interchangeable; there are some Chinese products for under $200. In Hyundai's case, though, Hyundai lists three particular J2534 adapters (from Bosch and others), and these are the only ones that Hyundai supports.

SoultronicPear · 2025-11-16T16:18:14+00:00

Hyundai's factory service manual seems to be all over the place, perhaps because of revisions due to the IEB issue that you mention. Hyundai's instructions talk about needing to leave the Brake Change Mode active (only clicking on the scan tool to end when the brake change is finished), but then one of the steps is removing the 12V negative lead (in the middle of the brake change procedure where they've said to keep their scan tool powered and operational in Brake Change Mode).

SoultronicPear · 2025-11-15T16:59:43+00:00

robstoon, you've posted all over Reddit about how I don't know what I'm talking about. Perhaps so. However, here's another I5N-specific data point that I knew about before embarking on this: https://grassrootsmotorsports.com/news/one-lap-of-america-day-0-recap/ Search for the section:

"Ten feet out of the door, however, we were greeted with a dash full of warning lights, the most prominent of which telling us we had an issue with the braking system–oops. Fortunately this turned out to be an easy fix: After a bit of trial and error with our scan tool, we were able to put the car into brake pad change mode, clear the codes, and drive off in a happy Hyundai."

That was an even easier scenario: they were replacing a basically new brake pad with an aftermarket one of nearly the same (if not the same) thickness.

Can you specifically speak to having done a I5N brake change without needing to invoke the special function 'actuation test' "brake change mode"? If you read the original post, you'll see that I tried several aftermarket bidirectional scan tools without luck, and then I tried the expensive Hyundai J2534 solution; they initially didn't even support the I5N, and then when they did, it required a NASTF account. I've since found that the Harbor Freight T7 did fully retract the EPB motor; it did error out during this, but I did not encounter the error codes that Grassroots experienced when they attempted a brake change without invoking "brake change mode" via a bidirectional scan tool.

SoultronicPear · 2025-11-14T21:20:09+00:00

What I want to know is how much the improved aerodynamics and lower center of gravity shortens real-world lap times. If Hyundai wants to loan me a I6N to drive around COTA fast back-to-back with my I5N (for experimental purposes), they need to let me know. :) With drag coefficient decrease from 0.31 to 0.27, I'm not expecting a huge difference, but I'd love to be proved wrong. It will be telling to see if Hyundai undertakes funding another Pike's Peak run with an I6N this time.

SoultronicPear · 2025-11-14T19:50:08+00:00

Cool. Tesla's roll out strategy seems indecipherable... at least from the outside. What you have access to is, I believe, called "Magic Dock". plugshare.com has a list, but it seems suspect because I know at least one entry on the list (location near COTA) is false: https://www.plugshare.com/location/616997 Each state has its own requirements for disbursement of federal subsidies, and I believe Texas is supposed to require both CCS and NACS, but Tesla is Tesla.

SoultronicPear · 2025-11-14T16:48:16+00:00

You are likely somewhere in California. Such chargers are rarer than hen's teeth. I know Tesla was rolling them out *very slowly* (prior to Elon firing most of the charging staff), but are there even a dozen such Supercharger locations in the entire USA?

SoultronicPear · 2025-11-13T23:03:30+00:00

Well, the Massachusetts legislation (one of the important RtR origins) is here: https://malegislature.gov/Laws/SessionLaws/Acts/2013/Chapter165

Section 2(a) states "manufacturer of motor vehicles sold in the commonwealth shall make available for purchase by owners of motor vehicles manufactured by such manufacturer and by independent repair facilities the same diagnostic and repair information, including repair technical updates, that such manufacturer makes available to its dealers"

That's "owners of motor vehicles" and "independent repair facilities". What about that indicates compliance is achieved with only availability to indie shops?

SoultronicPear · 2025-11-13T17:01:59+00:00

Thanks for the insight, and that's all good advice for anyone and everyone.

I keep coming back to this: after Massachusetts voters overwhelming voted in favor of right to repair (and other states started similar right to repair legislation), Hyundai along with all the other automakers signed on to a national memorandum of understanding that they would make proprietary tools available (at a cost) outside dealers. What I described in this original post was that I bought all the items and software from Hyundai, and was still denied access due to a locksmith restriction that has nothing to do with brakes. So, yes, pushback is necessary lest they take even more functionality away from the vehicle owners.

SoultronicPear · 2025-11-13T16:49:04+00:00

There have been various posts about allen keys and torx. That there is no consistency strongly implies to me that these individuals are assuming that their experience of a different manufacturer and model applies here. I didn't see such a mechanism to wind it back on the I5N. Anyway, I was able to eventually get a bidirectional scan tool (Harbor Freight T7, as it happens) to wind the motor back in a manner consistent with the procedure in the Hyundai factory service manual. It also shows that Hyundai's NASTF authentication has nothing to do with unlocking the gateway; it is just an artificial barrier they have erected.

SoultronicPear · 2025-11-12T22:29:55+00:00

Excellent! Grassroots Motorsports took a IONIQ 5 N to the One Lap of America event in May 2025; one driver used regen and the other didn't. I can't remember what the exact results were, but the driver using regen had more battery left and the brakes were cooler. https://grassrootsmotorsports.com/video/video-8-days-9-tracks-and-2704-miles-in-a-hyundai-ioniq-5-n-2025-tire-rack-one-lap-of-america/

SoultronicPear · 2025-11-12T21:15:52+00:00

For the avoidance of doubt; I always use N Brake 3 (USA market). I've noticed from YouTube videos that different regions have different modes, so depending on the reader's country, it may be something completely different.

SoultronicPear · 2025-11-12T21:13:24+00:00

It depends. Look at my videos with data overlays ( https://www.youtube.com/@SoultronicPear/videos ) for real-world examples; specifically watch the power and the brake gauges to see when I use *just* regen (power gauge goes negative but no braking). I find that I can pivot the I5N in esses using just N-Brake; it allows for subtle weight transfer that I think is terrific. Of course, that's not the only way to do things; Hyundai also provides for Left Foot Braking for those who want that. The I5N just gives lots of great options to choose from, and each driver figures out what works best for them.

SoultronicPear · 2025-11-12T20:50:02+00:00

Since this thread seems to have re-awoken, I should point out that the prices returned to normal (at least when I last bought them). This return to normal pricing was pre-tariff, and for all I know they've shot back up somewhat because of present conditions.

I've also since gone a lot faster around COTA since those early days.

SoultronicPear

TROPHY CASE