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So is there a way to know just HOW MUCH CHARGE the battery has? You peeps are scaring me to the point I think I need to carry a 12v battery jumper/charger with me ... :-( I really don't drive long distances very much - mostly just quick trips around town. Thus I plug into my 240v Charger about once every 7-8 days to get to 80%.
 

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There's not really any convenient way to determine 12V charge level, only by voltage once it's settled down or if it gets bad. It's disappointing that the root cause of this is still a mystery. A local Rolls Royce owner here had this happen after he left a window open and doors unlocked all night and his battery was a massive 960 CGA, twice what we have.

I'm not expecting this problem myself but I do carry light-duty jumper cables just in case.
I don't drive much either but I set the charge limit to 60% and plug in (230V 8A trickle charger) after any driving.
 

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Over the years there have been numerous threads on this subject. The cause has been elusive. The solution a bit of a faff but worth trying.

#1 - Buy a small 12v DC display from Amazon that plugs into the 12v dash socket and keep a wary eye on it to make sure the voltage doesn't drop.

#2 - Buy a new generation 12v DC 'Smart' charger that is also a battery conditioner and run that for at least 12 hours once per month whether the battery seems to need it or not. It's the conditioning feature that matters and that won't kick in until the 12v battery is full.

My Leaf 24 had the very same problem back in 2016 and after using this technique the very same 12v battery that was giving trouble went on for another three years without any further problems.

Check some of these forum entries for further details on this annoying EV feature.

 

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Just over 1yr old and done 17K miles.
I don't think it's the battery. It happened already once before and Huyndai tested battery ok. Sometimes the car is unused for a week and it still works perfectly. Now it started ok in the morning and it died after being 15 mins stationary.
Honestly it looks to me as some sort of temporary bug with 12v battery top up (software / DC-DC converter / something else?).

The car is with a dealer now so I will find out later today. But I'm quite sure they will say that batter test was ok and will just return the car.

However there is another recall that affected my car (came just recently) - HV junction box. They will look into this today and let me know if they can replace it and how long to wait for parts. I will post that as a separate thread.
 

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Just over 1yr old and done 17K miles.
I don't think it's the battery. It happened already once before and Huyndai tested battery ok. Sometimes the car is unused for a week and it still works perfectly. Now it started ok in the morning and it died after being 15 mins stationary.
Honestly it looks to me as some sort of temporary bug with 12v battery top up (software / DC-DC converter / something else?).

The car is with a dealer now so I will find out later today. But I'm quite sure they will say that batter test was ok and will just return the car.

However there is another recall that affected my car (came just recently) - HV junction box. They will look into this today and let me know if they can replace it and how long to wait for parts. I will post that as a separate thread.
Personally, I would change the battery whatever Hyundai said! That way, if it falled again ther eis much clearer proof it is likely to be something else!
 

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@Cody94549 ,
I will actually buy small battery booster - too much wasted time to wait for Roadside Assistance and it literally takes 1 minute to revive the car if you have it. I think the simplest booster will do as we don't need high amps to crank the engine. So it's worth to have it in my case. But I don't think you need to buy it yet if you never had problems with flat battery.
 

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When they tested my 12V battery after charging it overnight, it passed all the load tests. I think this is a problem with the car not shutting down properly sometimes to its lowest power state.

You can very easily test the 12V battery voltage - use a cheapo cigarette lighter socket voltage display; get in the car and press the start button WITHOUT pressing the brake. This starts the 12V electrics up but doesn't start up the high voltage side or the DC/DC convertor (i.e. it doesn't try to charge the 12V from the high voltage battery).

Mine hasn't failed since they did the full charge on it and I've disconnected the dashcam which was permanently connected but used in parking mode when the car was powered down. Since disconnecting it, I no longer get the "Warning, battery drain while powered off" message (or words to that effect). Time will tell...
 

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Have you seen Bjorn's video "Trick to avoid low 12 V battery on your EV"
Very interesting Andy, however the Kona has its own cool trick called "Auxilliary Battery Saver" which periodically fires up the HV battery to "top up" the 12V battery - you can tell when it's doing this because the light comes on in the front Hyundai badge. It runs for around thirty minutes.

This whole thread is about why the 12V battery goes flat in spite of this top up process!

John.
 

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Have you seen Bjorn's video "Trick to avoid low 12 V battery on your EV"
It doesn't explain how some people have started and driven the car for 10 minutes or so, when the battery should be charging, stop for a few minutes and when they come to start again it's dead.
It does seem that the Kona, or some of them, have a flaky charger or there are some iffy batteries in them.
 

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This is all symptomatic of a software bug which doesn't shut the car down into low power mode properly when all the doors and windows are shut and the car is locked. I can't believe so many cars from all ages - and therefore different batches of 12V batteries from suppliers - can share a hardware issue in this way. When they tested the 12V battery in mine, it was fine, after all.
 

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This is all symptomatic of a software bug which doesn't shut the car down into low power mode properly when all the doors and windows are shut and the car is locked. I can't believe so many cars from all ages - and therefore different batches of 12V batteries from suppliers - can share a hardware issue in this way. When they tested the 12V battery in mine, it was fine, after all.
I agree. This is not a 12v battery problem at all. Of course, there will be some that fail due to faulty manufacture, but the incidence will be similar across all models and motive power.

This is an inherent issue caused by all EVs method of maintaining voltage in the 12v DC battery as opposed to an ICE cars method of permanently running an alternator and relying on a regulation system to prevent overcharging despite the supply of current being constant. An EV doesn't do that but instead intervenes intermittently when triggered by various events.

This allows the 12v battery to discharge below its optimum level at times. And if that pattern happens frequently then the battery is damaged and eventually dies. But that death wasn't due to the 12v battery being faulty. It was killed by circumstances outside its own control.

Which goes back full circle to a need to investigate two aspects of this problem. First of all, what is causing the drain even if the car is switched off? And secondly why doesn't the re-charge system kick in to recover from that situation? And fail to do that on a random and unpredictable basis. Both of these aspects must be random or this problem would have been solved many years ago.

I reached this conclusion some four years ago. And eventually decided to just keep a close eye on the health of the 12v battery and manually intervene to ensure that it was always showing full voltage. That meant installing a small 12v meter into the power socket and using a 'Smart' charger overnight for at least 12 hours once per month to allow the conditioning feature to perform its witchcraft. After a few bizarre incidents prior to this regime the original battery then went on to operate flawlessly for another three years and all 12v DC-related problems went away.

For the sake of personal sanity, and peace of mind over not being stranded at some inconvenient time, I recommend this kind of preventative maintenance to all EV owners.
 

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I reached this conclusion some four years ago. And eventually decided to just keep a close eye on the health of the 12v battery and manually intervene to ensure that it was always showing full voltage. That meant installing a small 12v meter into the power socket and using a 'Smart' charger overnight for at least 12 hours once per month to allow the conditioning feature to perform its witchcraft. After a few bizarre incidents prior to this regime the original battery then went on to operate flawlessly for another three years and all 12v DC-related problems went away.

For the sake of personal sanity, and peace of mind over not being stranded at some inconvenient time, I recommend this kind of preventative maintenance to all EV owners.
Nice explanation.
  • Can you share which "12v meter into the power socket" you are using. And by "power socket", WHERE IS THAT specifically?
  • Ditto on the "Smart" charger ... Which one do you use?
Thanks
 

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  • Can you share which "12v meter into the power socket" you are using? And by "power socket", WHERE IS THAT specifically?
  • Ditto on the "Smart" charger ... Which one do you use?
I use one like this that also has a couple of USB outlets. There are hundreds around that are cheaper. As you can see it plugs into what used to be the cigarette lighter socket - now called the 12v power socket. That will be on the dash somewhere in full view whilst driving so that you can see the voltage at all times.


My 'Smart' charger model seems to have been discontinued after four years. Also, it was a UK mains model. You will need to search locally for one that matches your own mains voltage. The key is to find one that offers an analysis feature and can also condition the battery after it is full. The full sequence can take a considerable time though and it should be allowed to run its full course to gain the maximum advantage from its de-sulphide feature. Search for 'Smart' 12v battery chargers that also have a 'Conditioner' feature.

These are available in UK and will give an idea of what to look for.

 

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This is an inherent issue caused by all EVs method of maintaining voltage in the 12v DC battery as opposed to an ICE cars method of permanently running an alternator and relying on a regulation system to prevent overcharging despite the supply of current being constant. An EV doesn't do that but instead intervenes intermittently when triggered by various events.
This allows the 12v battery to discharge below its optimum level at times. ...
Yes, like being in RUN mode. Logging indicates that charging happens every few seconds and the average voltage level is exactly where you would expect it to be,13.8V.
Noting that the car has no problem driving for hours on end, the problem lies elsewhere.
 

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...
(I edited to the part I want to quote)

Which goes back full circle to a need to investigate two aspects of this problem. First of all, what is causing the drain even if the car is switched off? And secondly why doesn't the re-charge system kick in to recover from that situation? And fail to do that on a random and unpredictable basis. Both of these aspects must be random or this problem would have been solved many years ago.
I've mentioned before, maybe Facebook, that my recharge system tried it's best.
I've now forgotten if it was 10% (6.4kWh) or 10kWh that the big battery dropped overnight.
A huge drop that failed to save the 12v from being flat.
Hyundai replaced the battery, under guarantee I guess.
The only thing the mechanic asked was "Was the car on charge?"
The answer was "Yes, but it took nothing all night".
 

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Someone on the i3 Facebook page has been using this product to monitor the 12V battery. i3 owners seem to have much the same problem but many more years of experience dealing with it.
Search on ebay for "QUICKLYNKS Battery Monitor BM2 Bluetooth 4.0"

126663
 

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Hi, I'm afraid that I'm not very knowledgable re. car electronics.... any advice would be appreciated. I've bought a battery monitor that fits the 'cigarette lighter'. Starting the car (without my foot on the brake) shows a reading of 12.1volts. This goes up to 12.3volts when I start the car with my foot on the brake. Do these readings sound reasonable or should I be thinking of buying a power pack just in case? As I say, any advice would be appreciated!
 
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