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One way to do brake fluid replacement on a rational basis is checking the moisture content, and base it on that. There is a tool for that.
Yes, and checking is a lot cheaper than replacing.

But am curious what Kiwi said, and if there anything diff about EV brakes that would require more frequent fluid changes. I would have expected that EVs with their regen would need less replacement. My previous car, Prius, after 5 years and 95k kms had almost no wear brake pad wear. I never checked the fluid, but certainly the brakes had less wear and tear than a pure ICE car.
 

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I am guessing that brake fluid has no "wear" that depends on use. I believe a given brand of brake fluid, it absorbs moisture from the air at some time dependent steady rate ( possibly also depends on air humidity). I expect this to be independent on the usage pattern, but I could be wrong. Maybe more intense use, such as track or Taxi use, may operate at a higher temperature, which may
result in more water absorption and corrosion, I am unsure. I expect that regen braking would be friendly to the hydraulic brake system, resulting in less wear on all of the hydraulic
components.

I think it is more dependent on how anal an user or car maker is about the optimal performance of the brake fluid. I remember on my CLA250 benz, the dealer would change out the fluid ever couple of years. which I thought was unnecessary. The complexity of the braking system may necessitate a low viscosity fluid. I do not think there is too much else a brake fluid can bring to the table. Better (less) water absorption from the air, higher boiling point, corrosion inhibitors, and low viscosity. I finally looked up what the Kona EV owner's manual "recommends": Dot 4 LV ( Low viscosity) although they indeed recommend yearly "check", vs the ICE code only every 2 years.
 

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Not that I am recommending this, but I have never changed brake fluid in any of my past cars. A couple of them have gone over 300k kms. And that's not to say that I will continue that practice. But I may start checking it from time to time.

Remember, dealers are always looking for ways to do more maintenance on your car than necessary. And this is esp true with EVs, as we don't have the complexities and maintenance requirements of an ICE car. I think once the Kona recalls/fixes are done, it too, will require very little maintenance.

I had my Prius for 5 years, and only maintenance done was oil changes and tires. And I got a great trade-in price, 60% of what I paid for it. It was a good little car. And never had a recall, either,... haha. When Toyota finally comes up with their pure EV, I think it too, will be a big winner.
 

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My parents lived in Germany for 7 years and I worked there for a year in 1980. I had noticed that the M-B service agent attached a tag to the master cylinder of our car certifying that the fluid was changed and that was checked when my mother took the car in for the biennial TuV vehicle inspection. Not long after that a work colleague had the brakes fail on his VW bug due to fluid boiling after he drove with the hand brake partially on. Since then I've been aware of these potential issues and of-course have acquired equipment to efficiently change the fluid on my own conventional cars.

Almost every master cylinder is vented to atmosphere to allow the fluid level to fall as pads wear. A few examples (Delco-Remy '60s-'80s?) had a bellows to compensate for the volume change. The vent, where used, is often hard to spot, just a small razor slit or pinhole in the rubber gasket. Another contributor to air entry is that the fluid level "breaths" slightly when the pads go from the just-relaxed position to being bumped out a tiny bit more when the disks flex under wheel loading. In fact disk brake technology relies on that phenomenon to acquire pad clearance to the disk. Manual clutch hydraulics experience a similar effect at the throwout bearing due to crankshaft endfloat.

So, the brake fluid can absorb moisture both from what wanders through the vent and the slow exchange of that air due to the latter process. I have noticed how the fluid in the reservoir seems to deteriorate faster than what comes out of the calipers but I would expect that in-theory moisture should eventually be absorbed uniformly in a hygroscopic fluid.

The Kona's system (see second graphic) is perhaps three times more complicated than a conventional system, additionally containing an integrated second motor-driven master cylinder and a handful of electric and check valves to effect the combination of regen and braking. It's clear from an engineering perspective that there is a design balance required between using conventional, established, safety-proven systems to avoid getting sued, and the main goal of designing an efficient EV ... otherwise it might all be done electrically. As best as I have noted, every EV has a similar system, including GM's EV1 from the '90s, see first graphic below.

My dealer did my scheduled brake fluid change a few weeks ago at my second service and I'm fairly certain they used a pressure flusher and possibly an OBD routine to cycle the valves and pump fluid through. I noticed 12V battery activity throughout the service and they billed me for 1 litre, about what I would expect. I checked all the bleed nipples and it appeared all had been recently opened as they were wet. The fluid change is not optional in the EU schedule as it appears to be in the US one. That could be because an inspection using a proper instrument may allow for a change to be delayed if the moisture content is within spec, or simply allowing the legal right to ignore conventional maintenance without that affecting warranty obligations or rights.

The cost of damaged brake system parts in a Kona is something I would not want to find out just because I wanted to save a few dollars. Plus, if it's required to maintain the warranty I'm hardly going to to argue the point with a service advisor.

5144


5145
 

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That's a long answer, but thanks. I think at the least I will check my brake fluid for moisture.
 

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anyone know, what years for U S cars?..............

More than a dozen Kona Electric models internationally have caught fire, although none have been reported in the U.S. According to reports, the software upgrade had been performed on the affected vehicle in the last reported fire.
Hyundai Motor America confirmed to Green Car Reports that the battery-pack replacement effort includes U.S. and Canadian vehicles. "We are working closely with NHTSA and Transport Canada on the recall and will communicate the details to affected customers shortly," it stated.


Did last battery recall, reduce our mileage by 10%? ..........

Quote: The recall follows one announced in October in which Hyundai upgraded the battery management software and in some cases limited the maximum state of charge to 90%. In the U.S., that also involved a physical inspection of the pack at the dealership, and an advisory to park the vehicle outdoors and/or away from structures until the remedy.

thanks,
 

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No word from the NZ importer yet, but it would be hard to believe they wouldn't play along. We have nearly the same total numbers due to the Kona being introduced about 10 months earlier than Aus. I can't even imagine how long this will take, a year perhaps? They'll almost certainty apply a recommended or software-enforced limit on charging level in the meantime. Apparently it's 90% in S.K. but I'm not sure how that's implemented.

EDIT: Spoke 1/2 a day too soon, my importer has just notified me by email that they will let me know what's going on once they figure it out themselves.
 

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Indeed, they gotta manufacture a lot of battery packs, then ship em, then install em. 90% would break my commute routine significantly, I would have to charge nightly instead of every second day. If a better car is available in the meantime, I'll deffo consider swapping.
 

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Indeed, they gotta manufacture a lot of battery packs, then ship em, then install em. 90% would break my commute routine significantly, I would have to charge nightly instead of every second day. If a better car is available in the meantime, I'll deffo consider swapping.
Warranty replacement is an interesting concept. If Hyundai wants to be technically compliant (at least under Aus consumer laws), they only have to fit sufficient batteries to supply 80% power after 8 years from date of original purchase.

So if they recall my Kona in August 21 it will be 2 years old, and they would only be obliged to provide sufficient batteries to provide 51 kWh in 6 years time. Or to put it another way they can leave out 13kW worth of batteries during the changeover.

I think it unlikely they would do this because of public relations, & good will. Not to mention redesign of battery bay & other components. On the other hand, when you’re talking about a program costing $900,000,000 even small tweaks could save millions.

[edit: tried to make explanation simpler 😳]
 
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Just musing, what does Hyundai, and/or LG, do with 82,000 (relatively new) battery packs that might blow up?
 

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Just musing, what does Hyundai, and/or LG, do with 82,000 (relatively new) battery packs that might blow up?
Maybe we'll see a new cheap Hyundai model come out, which looks very much like a Kona, with battery exactly the same size and weight. But it will only have 51 kWh charge capability... And there will only be 82,000 sold... 😄
 

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Occam’s razor result: while nobody knows the cause, dendrites in batteries are most likely culprit.

[edit: and dendrite formation is more likely when charging to 100% of battery capacity. Which is why GM & Tesla are now limiting max charging to 90-95% through software updates to try & avoid replacing batteries. So I'm not fully charging Kona until it’s batteries are replaced.]
 
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