Thanks for confirming. That is the fatal flaw with some EVs 12V battery charging systems. They don't respond and intervene when the 12V battery is close to dying. It's just a dumb timer. If timer happens to turn on at the right moment, you might get lucky and it will actually do what the name implies - "Battery Saver".
12V battery
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KiwiME
Well-Known Member
I believe this is how it works: If the test load (inverter) negative terminal was connected to chassis ground (as it should be) the energy drain would be logged by the IBS sensor on the battery negative terminal, which is always active. When the BMS system wakes up (daily on old BMS software, every 4 hours on the new, or at the start of a Run, Charge or Utility mode event) it will download the logs over the serial data connection and recalculate the auxSoC from the prior value.
Based on that the BMS may adjust the duration of the constant-voltage charge period if necessary. We've seen that adjustment appear on a small number of occasions with BM2 data, on both the old and new software. Certainly on the old software the most change I've personally seen is 30 min instead of 20 min, or once or twice even zero.
However, it's worth noting that the actual charge energy profile during those constant-voltage events in normal cases is very much biased to the first few minutes, because the battery recovers quickly. But, in the case where the battery is damaged it will fail to accept the required charge under those conditions.
IMO, problems arises if:
(a) the energy loss is excessive during the dwell period, exceeding the system's range of recovery charging time.
(b) the drain was drawn directly off the battery, bypassing the IBS.
(c) the battery has suffered a severe discharge such that it's damaged and requires a different charging regime.
I kind of figured this is the case therefore when running my 100 W inverter ( through the 12 V accessory outlet), I leave the car on (run mode) or utility mode to keep up.
The Aux battery saver + disappeared with the 960 software update campaign for those who had it successfully applied as discussed previous (for earlier models).
I saw zero evidence of Aux battery SOC playing any role in 12V charging times on my Niro. When left parked unused for several weeks, the Aux SOC % just gradually declined from 90% down to 60% SOC despite the automatic daily 20 minute charges (charging current on each of those sessions dropped to ~0 after only a few minutes). Once SOC got down that low, I intervened and manually charged it back up to 100% reported SOC using utility mode. Ignoring the declining reported Aux SOC %, the voltage on the battery itself always remained above 12.6V when there was no load. It would drop down 12.0-12.1V with load of turned on car.
I often wonder who writes the service manuals for these cars and if they even bother talking to the engineers. I've never had any 12V battery issues on my 3 year old Bolt EV but my experience with the Niro made me curious how that car behaves. The service manual for that car claims that the car will turn on automatically if the battery falls below 12.4 volts. To test that claim, I slowly discharged the 12V battery (using both external loads and in-car accessories). I watched as the voltage dropped down to 12.0V with no signs of any charging activity. I left it at that level overnight with no signs up any charging. Having given up on the experiment, I plugged in the EVSE and the car immediately turned on and started drawing 100W from the wall to charge the 12V battery. After about 45 minutes it stopped charging. So it looks like it only realized the 12V battery was low when I connected the charge cord. The main traction battery was above 50% the entire time so plenty of juice for the car to use. If I find myself with a disposable 12V battery, I may conduct this experiment again to see if it would ever turn on before the 12V battery completely drains.
In conclusion, the 12V charging is a mystery for many EVs. Don't assume anything you read in the service manual has any bearing on reality.
I often wonder who writes the service manuals for these cars and if they even bother talking to the engineers. I've never had any 12V battery issues on my 3 year old Bolt EV but my experience with the Niro made me curious how that car behaves. The service manual for that car claims that the car will turn on automatically if the battery falls below 12.4 volts. To test that claim, I slowly discharged the 12V battery (using both external loads and in-car accessories). I watched as the voltage dropped down to 12.0V with no signs of any charging activity. I left it at that level overnight with no signs up any charging. Having given up on the experiment, I plugged in the EVSE and the car immediately turned on and started drawing 100W from the wall to charge the 12V battery. After about 45 minutes it stopped charging. So it looks like it only realized the 12V battery was low when I connected the charge cord. The main traction battery was above 50% the entire time so plenty of juice for the car to use. If I find myself with a disposable 12V battery, I may conduct this experiment again to see if it would ever turn on before the 12V battery completely drains.
In conclusion, the 12V charging is a mystery for many EVs. Don't assume anything you read in the service manual has any bearing on reality.
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KiwiME
Well-Known Member
But as we've seen, the setting disappeared while the function did not.
hobbit
Well-Known Member
I happened to spot an interesting mention from a few days ago by Richard Gledhill over at
SpeakEV, who suggests that the AGM supplied by the manufacturer might be a calcium
variant, which might explain the inordinately high charging/float voltage. I scrutinized
every label on my "Rocket" unit, and there's no specific mention ... but we'll note the model
number: CMF45L-DIN. And over at Rocketbatt.com we find a certain similarity under the
"car segment" listing ... the "calcium MF" series, implicitly suffixed with "DIN". That's a set
of industrial standards , probably having to do with the form factor.
I'm not saying it clinches anything, but I'm worrying a little less about that almost-15-V thing.
_H*
SpeakEV, who suggests that the AGM supplied by the manufacturer might be a calcium
variant, which might explain the inordinately high charging/float voltage. I scrutinized
every label on my "Rocket" unit, and there's no specific mention ... but we'll note the model
number: CMF45L-DIN. And over at Rocketbatt.com we find a certain similarity under the
"car segment" listing ... the "calcium MF" series, implicitly suffixed with "DIN". That's a set
of industrial standards , probably having to do with the form factor.
I'm not saying it clinches anything, but I'm worrying a little less about that almost-15-V thing.
_H*
apu
Well-Known Member
Interesting, it looks like they recently replaced my original failed AGM battery with a Hyundai flooded lead acid battery. It will be interesting to see how long it last with a charge profile geared for AGM.
gnarlsagan
New Member
Add another dead 12v battery to the list. Went to start the car yesterday and nothing happened. Realized that we couldn't even unlock the back hatch. Seems there was only enough battery left to unlock our car once.
Tried charging the car and it wouldn't charge, and our MyHyundai app said our car was at 0%. Since we weren't sure what to do, ended having the car towed to the dealership a couple miles away. Today they replaced the 12v battery, and couldn't tell us why it died. The main battery had 94% remaining. Our car is three months old with almost 3k miles on it.
Not sure if we got the update people have been talking about, but this experience was definitely not a pleasant or reassuring one.
Tried charging the car and it wouldn't charge, and our MyHyundai app said our car was at 0%. Since we weren't sure what to do, ended having the car towed to the dealership a couple miles away. Today they replaced the 12v battery, and couldn't tell us why it died. The main battery had 94% remaining. Our car is three months old with almost 3k miles on it.
Not sure if we got the update people have been talking about, but this experience was definitely not a pleasant or reassuring one.
Bob Long
Member
Sorry to hear about your 12v battery. I know the feeling and frustrations you’re having. Incidentally I was reviewing some EV’s on YouTube last night, and the MG ZS EV has a 12v battery indicator on the screen. I think it’s the only EV I have seen with that feature. I wished our Kona had this too. It’s going in for a software update next week, but I think that may be because of the fires they have been having recently 
Good luck and keep me posted
The 12v battery display is at the bottom to the left.
Good luck and keep me posted
The 12v battery display is at the bottom to the left.
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Esprit1st
Well-Known Member
Unfortunately this is pretty common. Although I NEVER had this issue and I own my Kona for close to 2 years now.
Make sure that the car is turned off. And all doors (including back hatch) are closed. There is an issue with the little plastic rubber stoppers sometimes not being right all the way, which sometimes prevents the hatch from closing all the way. I guess the light stays on and the car doesn't turn itself off completely, thus draining the battery.
Toolworker
Well-Known Member
I have this problem repeatedly and posted examples earlier in this thread including a video of my AeroVironment EVSE in a loop draining the battery.
Until Hyundai admits this problem and fixes it, those of us who have it have to live with it - #HyundaiBetaTester. Suggest you buy a small battery jumper. It takes about a minute and a half to restart the car and only draws about 30A, so a small unit will work. I keep mine right behind the fold-down rear seat so I don't have to open the trunk to get at it.
Were you plugged in? It only occurs for me when plugged into an EVSE. The AeroVironment can actively discharge the battery. The Hyundai EVSE cord doesn't do that, but seems to occasionally disable ABS+ and the battery dies slowly.
I am going in for the exploding battery recall tomorrow and will document this. It'll be the second time I have it on a service report. Three times and I can file a lemon law request for Hyundai to repurchase. Nothing else has gotten their attention but this might.
This sounds more like a problem with a specific EVSE (perhaps the entire brand, I don't know), never have had this happen with any of the Level 2 EVSEs I have used:
Charge point
Clipper Creek
Siemens
Tesla Destination Chargers with adapter
EvGo
Electrify America
ABB
So I suspect this may be where your problem lies, not in the car itself.
Toolworker
Well-Known Member
The battery also dies occasionally when plugged into the Hyundai charge cord, just in a different way. So it's not the specific EVSE.
Bob Long
Member
No, all interior lights switched off including headlamps and trunk. This has happened on four occasions in 3 years, twice in our Kia Soul and twice in the Kona, completely dead 12v battery. I got paranoid and deliberately turned off the interior lights during our long summer nights here in Norway, but I still ended up with flat 12v batteries. All EV manufacturers need to display the state of the 12v battery on the screen, the same as it is on your mobile phone! No point having a fully charged main battery if the damn thing won't start because of a flat auxiliary battery! You were very lucky to have had no issues in your two year old Kona, but you cannot tell me the state of your battery without using a meter on it! Another suggestion is to use small lightweight lithium batteries which are more reliable. Our existing batteries are old hat....!
Bob Long
Member
The display of your 12v battery should be clearly displayed on the screen. Would you drive a petrol or diesel car without a fuel gauge? It even got to the point whereby the dealer at the Hyundai service centre said to charge the 12v battery once a month! Tell that to an old lady living in a block of flats with no garage. If that was the case then Hyundai should supply a 12v battery charger. This is a serious issue that needs to be addressed.
The 12 volt battery is no different to those in gas cars, they don't display the charge of the 12 volt battery either, so why should an electric vehicle?
John McLellan
New Member
Query?? When you measured the battery voltage with car off did you disconnect any of the leads? There would be Parasitic loads affecting voltage voltage