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During dealer visit cars are not always hooked on 12V battery charger, esp. during short tasks, quick checks, etc. Employees assume the 12V battery is healthy and can sustain 10-15 minutes of discharging during service checks before releasing the car to customer. So the 12V battery is often at lower SOC than before the visit.

It could indeed be drained down to 31% SOC, after 20 minutes in ignition active mode, if 12V battery tender was not connected. Normal driving will eventually bring 12V battery back to 90% SOC.
 

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Anyone have any thoughts of putting something like a small cheap PWM solar charge controller and a 20 or 50 watt solar panel somewhere to avoid this ridiculously stupid problem? Issues I see are aesthetics, mounting the panel somewhere, and aero... but would a small solar controller piss off the BMS in the car?
 

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Discussion Starter · #23 ·
Anyone have any thoughts of putting something like a small cheap PWM solar charge controller and a 20 or 50 watt solar panel somewhere to avoid this ridiculously stupid problem? Issues I see are aesthetics, mounting the panel somewhere, and aero... but would a small solar controller piss off the BMS in the car?
This isn't the issue. You're not running out of energy, what's happening is there seems to be about a 3 watt draw all the time. That's a lot and the 12v can't take all the charging and discharging.

So the fix is an aftermarket lithium iron phosphate battery. Ohmmu sells one for $440.
 

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Discussion Starter · #24 ·
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And even that may not be the problem. This looks broken. It charged the 12v once, then charged it 5 more times 4 hours later. It doesn't even appear to be necessary, the voltages are over threshold.

This looks like a software bug, if this happens often this is killing the 12v battery. Note that the car was quiescent: I didn't bring the key near it, nor did I touch it this entire timespan, from 5pm (1700 hours) onwards. Around 1300 is a snack run to a nearby store, the 2 spikes in close proximity are it charging each way. Interesting to note that the car regains nowhere near enough energy from brief drives to keep the 12v battery up. This was not the case for my toyota Prius, I drove it briefly all the time, doing this solely for weeks, and it never had any 12v issues.

From my day job as a computer engineer this looks like a problem.
 

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Anyone have any thoughts of putting something like a small cheap PWM solar charge controller and a 20 or 50 watt solar panel somewhere to avoid this ridiculously stupid problem? Issues I see are aesthetics, mounting the panel somewhere, and aero... but would a small solar controller piss off the BMS in the car?
No, as the car does try to keep the 12v charged.
 

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Ioniq 5 72,6kWh RWD Lucid Blue
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I’ve done a little test the last week, as this problem intrigues me.

I’ve read somewhere that the BMS does top up the 12V when car is off, but only when SoC is between 35% and 80%.

so I drove the car down to 30% SoC, before I left it in the driveway for 4 days (business trip), didn’t use bluelink or touched the car at all during that period.

came home and used my voltmeter, 12.2V. Drove it down further to around 10% during the next couple of days, battery down to 12.1V.

recharged from 10-100%, and drove the car down to 83%, and left it to next day, 11.9 next morning.

Drove it to work again, parked it overnight at home at 71%, measured 12.7V next morning.

Plugged in my OBD2 reader for all my drives during the last week, battery charged at 13.6-13.7V constantly when driving. But as my commute is only 25 minutes each way, that’s not long enough to have a serious impact on 12VSoC.

This totally unscientific experiment shows support of the theory that the 12V is only charging when a) you’re driving the vehicle and b) when vehicle is off and SoC is between 35 and 80%.

This needs more testing, but a good rule of thumb should be to leave the car at just below 80% if you don’t drive it for a while.
 

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Discussion Starter · #27 ·
I’ve done a little test the last week, as this problem intrigues me.

I’ve read somewhere that the BMS does top up the 12V when car is off, but only when SoC is between 35% and 80%.

so I drove the car down to 30% SoC, before I left it in the driveway for 4 days (business trip), didn’t use bluelink or touched the car at all during that period.

came home and used my voltmeter, 12.2V. Drove it down further to around 10% during the next couple of days, battery down to 12.1V.

recharged from 10-100%, and drove the car down to 83%, and left it to next day, 11.9 next morning.

Drove it to work again, parked it overnight at home at 71%, measured 12.7V next morning.

Plugged in my OBD2 reader for all my drives during the last week, battery charged at 13.6-13.7V constantly when driving. But as my commute is only 25 minutes each way, that’s not long enough to have a serious impact on 12VSoC.

This totally unscientific experiment shows support of the theory that the 12V is only charging when a) you’re driving the vehicle and b) when vehicle is off and SoC is between 35 and 80%.

This needs more testing, but a good rule of thumb should be to leave the car at just below 80% if you don’t drive it for a while.
Yeah you should get an actual battery monitor that constantly logs. One because Hyundai isn't accepting my bug report, and two, because you will find the threshold isn't 35 percent. It's lower, unsure how low but I have measured battery saver when the car indicates 34 percent.
 

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Yeah you should get an actual battery monitor that constantly logs. One because Hyundai isn't accepting my bug report, and two, because you will find the threshold isn't 35 percent. It's lower, unsure how low but I have measured battery saver when the car indicates 34 percent.
Maybe it’s 33%?
Or 32?
Idk, and there’s a limit for how much time and resources I plan to spend to find that exact number, I leave that to others.
I plan to stay between 40 and 80% SoC in the future to avoid depleting the 12V battery, I also carry a booster in case it does anyway.
 

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Yeah you should get an actual battery monitor that constantly logs. One because Hyundai isn't accepting my bug report, and two, because you will find the threshold isn't 35 percent. It's lower, unsure how low but I have measured battery saver when the car indicates 34 percent.
How goddamn annoying is that? My EV6 is at the dealership right now for this and about 10 other issues and literally every even modestly technical problem becomes "we couldn't reproduce the issue." They tried to reproduce my DC fast charging issue by plugging it in to a 5kW level 2 outlet.
 

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Hello,
We have had our I5 since late December of last year. Going on almost 9.5k miles. Just picked it up from the dealer tonight for the second time. Twice with an SOC below 20% we have walked outside and the car has been totally dead. 12V dead. Drive battery at 12% first time, today at 11%. First dealer replaced a control unit and we thought that was it. That was in March I believe. Today the dealer told us we cannot let the car sit with an SOC below 20% or it will not charge the 12V battery? This time I think the car sat for 48 hours. First time was longer, maybe 4 days. My first thought is who needs a 20% drive battery if the 12V battery is dead? Can't drive it anyway! My next thought is how can a 12V car battery not sit for 2 days without dying? You can leave an ICE car for weeks, hop in, and it starts right up. After reading through this thread it seems the draw from the car is pretty substantial. What is the amp draw while asleep, I saw 3 watts above but what is the actual amp draw? I am starting to think this battery may already be going out..... Any thoughts or recommended next steps? I want to call Hyundai of America and try to get these problems well documented but I doubt it does much. Telling a customer you can't park your car with an SOC under 20% also sounds ridiculous to me. I may also be in the boat this seems like something that could be fixed in an update. Curious to hear some thoughts. I have yet to speak to the service manager, only had the writer who just regurgitates what he is told to say. BESIDES this, I love this car. I was a hater at first but the more I drive it the more I am digging the EV world. Thanks!
 

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Discussion Starter · #31 ·
Hello,
We have had our I5 since late December of last year. Going on almost 9.5k miles. Just picked it up from the dealer tonight for the second time. Twice with an SOC below 20% we have walked outside and the car has been totally dead. 12V dead. Drive battery at 12% first time, today at 11%. First dealer replaced a control unit and we thought that was it. That was in March I believe. Today the dealer told us we cannot let the car sit with an SOC below 20% or it will not charge the 12V battery? This time I think the car sat for 48 hours. First time was longer, maybe 4 days. My first thought is who needs a 20% drive battery if the 12V battery is dead? Can't drive it anyway! My next thought is how can a 12V car battery not sit for 2 days without dying? You can leave an ICE car for weeks, hop in, and it starts right up. After reading through this thread it seems the draw from the car is pretty substantial. What is the amp draw while asleep, I saw 3 watts above but what is the actual amp draw? I am starting to think this battery may already be going out..... Any thoughts or recommended next steps? I want to call Hyundai of America and try to get these problems well documented but I doubt it does much. Telling a customer you can't park your car with an SOC under 20% also sounds ridiculous to me. I may also be in the boat this seems like something that could be fixed in an update. Curious to hear some thoughts. I have yet to speak to the service manager, only had the writer who just regurgitates what he is told to say. BESIDES this, I love this car. I was a hater at first but the more I drive it the more I am digging the EV world. Thanks!
P=IV. V=12 volts. Power = 3 watts.
Therefore, I = 3 / 12 amps. Or 0.25 amp or 250 mA.
 

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P=IV. V=12 volts. Power = 3 watts.
Therefore, I = 3 / 12 amps. Or 0.25 amp or 250 mA.
V isn’t 12, it’s somewhere between 11 and 15 depending on SOC and whether it’s being charged, but regardless, that’s about right. The 3W figure comes both from direct measurement with a DC current clamp, and from estimation based on reported 12V SOC decay. It’s also average - in practice it’s not perfectly consistent.
 

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Hello,
We have had our I5 since late December of last year. Going on almost 9.5k miles. Just picked it up from the dealer tonight for the second time. Twice with an SOC below 20% we have walked outside and the car has been totally dead. 12V dead. Drive battery at 12% first time, today at 11%. First dealer replaced a control unit and we thought that was it. That was in March I believe. Today the dealer told us we cannot let the car sit with an SOC below 20% or it will not charge the 12V battery? This time I think the car sat for 48 hours. First time was longer, maybe 4 days. My first thought is who needs a 20% drive battery if the 12V battery is dead? Can't drive it anyway! My next thought is how can a 12V car battery not sit for 2 days without dying? You can leave an ICE car for weeks, hop in, and it starts right up. After reading through this thread it seems the draw from the car is pretty substantial. What is the amp draw while asleep, I saw 3 watts above but what is the actual amp draw? I am starting to think this battery may already be going out..... Any thoughts or recommended next steps? I want to call Hyundai of America and try to get these problems well documented but I doubt it does much. Telling a customer you can't park your car with an SOC under 20% also sounds ridiculous to me. I may also be in the boat this seems like something that could be fixed in an update. Curious to hear some thoughts. I have yet to speak to the service manager, only had the writer who just regurgitates what he is told to say. BESIDES this, I love this car. I was a hater at first but the more I drive it the more I am digging the EV world. Thanks!
Get the battery replaced. You should ask the dealer to do a simple load test on the battery. If you do have an abnormal current draw then the dealer should be able to diagnose that with a simple DC amps multi-meter
 

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Get the battery replaced. You should ask the dealer to do a simple load test on the battery. If you do have an abnormal current draw then the dealer should be able to diagnose that with a simple DC amps multi-meter
their problem sounds exactly like mine, and if the battery SOC is decreasing at 3W at the same time as 3W is coming out of the battery, the battery ain’t faulty.
 

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their problem sounds exactly like mine, and if the battery SOC is decreasing at 3W at the same time as 3W is coming out of the battery, the battery ain’t faulty.
Please check out this post where Ixlr8 took the time to do the actual amperage measurements! When idle, the car should be drawing 9mA or 114 mw. If the car is drawing 3W then you have a serious parasitic drain. Best course of action is to check the battery first using a load test. If battery checks out ok, then next is to find the parasitic drain
 

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I’m not arguing that the behavior is normal. I’m arguing that “why isn’t my car going into the proper low power state” is the problem to solve, and the battery itself is ABSOLUTELY not at fault. Also the fact that my car no longer tops up the battery while sleeping is a separate problem unto itself.
 

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But why are you making the assumption that he has a 3W parasitic leak? He could also have a bad battery. He should check both to be sure.
that’s true - he could have a faulty battery AND somehow otherwise identical symptoms. But if there’s a faulty battery anywhere, it’s caused BECAUSE of this power state issue cycling it too much. That and Occam’s razor.
 

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that’s true - he could have a faulty battery AND somehow otherwise identical symptoms. But if there’s a faulty battery anywhere, it’s caused BECAUSE of this power state issue cycling it too much. That and Occam’s razor.
Funny, I don't see how his symptoms are identical to yours given from his description. He has taken no current measurements, etc. He has a battery that has died on him twice, and doesn't hold a charge. Regardless of how it got there, he needs to check the both the state of the battery, and then determine if there is a parasitic draw. There are many posts here about cars being delivered with sulfated batteries due to the long delivery times on ship, train, etc from Korea. There is the possibility that the battery was in a poor state to begin with and never recovered. Jumping to the conclusion that the issue is due to a parasitic draw only and the battery is fine is not correct in my opinion.
 
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