12V battery

First of all, I do have a fuel gauge in my car! The high voltage battery is the gas and both cars, ice and EVs have a 12V battery for electric loads while the engine is off. Both cars work basically the exact same way.

Ice car batteries have the same problem when it's cold outside. So it's not like this is a totally new problem nobody has ever heard of.

The challenge, as it seems, is that manufacturers (apparently pretty much every EV on the market has been affected by this problem) haven't figured out a good (software) mechanism to charge the battery correctly.

Why that is, yes, it's a mystery to me too. I only know about the Hyundai approach. The battery saver plus option sounded like a great idea, checking the SOC of the battery every 24 hours and charging it. I'm not sure why they did that always for only 20 minutes. I'd charge it until it's 90% and good. Then keep checking every 24 hours.

But I'm not an engineer, so I don't have a clue ...

BTW, there is 12V battery meters for the cigarette lighter for a few bucks on Amazon. So you don't need to go all fancy with an OBD2 reader. In fact I had a Bluetooth to FM Radio dongle in my former Toyota Corolla which also displayed the Voltage. And it was less than $10.

 

The difference is that a 12 volt battery in an ICE car gets charged by the alternator and causes very little problems. With EV's you're relying on the electronics and you haven't got a clue whether your auxiliary battery is at 100%, 67%, 34% or dead. I have been driving petrol and diesel cars for 55 years without any real issues. I have 6 years of EV experience with nothing but 12v battery issues!

 

The newer ICE cars also have a lot of 12V battery problems, due to the parasitic drains, not unlike our EV. I think the previous BMS update helped to keep our 12V charged more often, and the little grille light comes on then. But yeah, if you leave your hatch open, or something else on, it will drain, same as with an ICE car.

 

Too bad the 12V socket is in the cubby under the central console where you can't see it

I wonder what the "parasitic" load on the 12V battery is when the car is off. Might put my DC clamp meter on it when I get home and see if I can get any meaningful reading.

 

I've got one of these now to monitor my 12V. Nice thing about it is that it also shows history, not just a real time instant.
https://www.insideevsforum.com/community/index.php?threads/installing-an-inexpensive-12v-battery-monitor.8391/

 

And wouldn't you know - right after posting this, I tried to start the car and it wouldn't. It had enough 12v to turn on and to open the trunk, but not enough to enable propulsion.

Fortunately I do have that little battery jumper pack, so started it up that way and went about my errands.

It's the first time it's ever gone dead while not plugged in, but at this point, having been discharged half a dozen times, the 12v battery might not be real healthy. I had already disconnected the BM2 for tomorrow's recall appointment, so have no data.

 

Science has been done!

At this point I had just gotten home after a ~5 mile commute. Car had been sitting in the driveway for maybe 20 minutes. Ambient temp was about 35F (1.7C)

I did notice an orange plunger by the hood latch, presumably an HV safety interlock? Nothing changed when I held it down. I checked that the meter was properly zeroed out several times while taking these measurements. Note that a negative current in this case means the battery is discharging, based on the way the cable is clamped.

First pic: Car locked, everything closed except the hood. -3.5 Amp





Second pic: Charge cable plugged in, vehicle is waiting to charge based on timer. -7.1 Amp




Third pic: Car is charging (timer override) on 120V, limited to 1KW. +9.0 amps steady, though it briefly peaked at over -12 amp during the charge startup sequence. I heard some clicky-klunks of the charge cable locking and contactors pulling in, and a pump whirred somewhere for a few seconds. Once it started charging things went quiet and the current climbed to +9.0 amps over a few seconds.




So unless something changes, leaving your vehicle plugged in and waiting to charge on timer on a cold day might be the worst thing you can do; it puts a solid drain on the 12V battery and I don't know if/when that drain ever goes away (I bet it doesn't! Probably keeping the computer alive). If it's really cold out, your main battery is really low and the 12V battery is marginal, I think it might be possible to kill the electrics completely doing this.

 

Did you close the bonnet/hood, or trick the latch with a screwdriver when measuring ? I vaguely recall that if left open, the car never goes to sleep.
I think it takes at least 5-10 mins to fully go to sleep even when everything is closed

 

I did not. Though I did prod the obvious orange plunger, I didn't hold it down for more than a minute. Weather permitting I'll try again and see what I can do to trick the car into thinking the hood is closed and see what happens over a longer stretch of time.

 

From memory I think it's just a case of pushing a horizontal screwdriver blade down into the latch to emulate the loop of the catch on the hood

The orange plunger is nothing to do with this - it's just a way to release the plug if the normal motorised release fails for whatever reason

 

I've only had an issue with the 12 volt battery in an EV once and that was the battery died after 6 years of use.....knock on wood, no other issues. If you are having so many issues, I would suggest getting one of the small lithium ion jump packs and keeping it in the glove box, then you can just jump start the car. Most will be good for about 30 jump starts of an EV on one charge, some up to 150 or so.

 

I'm struggling with the local dealer's inability (or refusal) to get a Hyundai engineer to look at these graphs showing how my 12v battery died, and then did not run ABS+ while at 12.1v for two days. I'm trying to keep the other discussion on tactics while posting the technical stuff here.

It's died about half a dozen times since I got the car in January, as documented extensively earlier in this thread. It's always died while plugged into either my Aerovironment EVSE or the Hyundai EVSE cord, until this week when it died while unplugged.

Last month, I noticed the dead battery while, fortunately, there was still enough voltage to maintain the BM2's data. It had been plugged into the Aerovironment EVSE, and on 10-13 got into a loop I've seen before, where the car keeps turning on, trying and failing to start charging, and turning off again, draining the 12v battery in short order. Around 17:00 I found the battery mostly drained, jumped it and left the car on for a few minutes. This brought it up to about 12.2 volts.

Then I thought to try it with the Hyundai cord, so plugged that in and left it. As the graphs show, over the next 40 hours nothing happened, including ABS+, except for one brief blip. The voltage remained at about 12.1 - 12.0 volts. When I unplugged the charge cord on 10-15, ABS+ resumed normally.

All this is consistent with what I've observed repeatedly over the past 9 months, except dying while unplugged.

I'm still on the original 12v battery. As I said, several days ago it died again, for the first time while unplugged. I theorized that the battery was finally worn down from so many deep discharges and died on its own, but the service tech says the battery is good and it has not died since. I had removed the BM2 as a precaution before bringing it in for service, so have no data on this failure.

 

I spent more time than I intended on this but I think the IBS sensor or its connections are faulty, although I don't envy the battle you'll have with Hyundai to get that replaced. Also, it seems pointless beating the aux battery to death with the Aero EVSE when it clearly doesn't work with the Kona. No doubt you've seen this thread?

 

Thanks for the suggestion. Is there anything I can tell the tech that might convince him to try replacing the IBS sensor?

No, I hadn't seen the other comment about the Aerovironment. Mine doesn't act that way - it always charges just fine. But every month or two, with nothing special going on and the Kona fully charged, it gets into this fight with the car.

I'll touch base with the Aerovironment engineer who told me they didn't have other Kona EV reports, and see if they have any now.

 

Why do you think it's anything to do with the 12v sensor ?
Seems more likely that the OBC or charging control is having some issue with the EVSE that's stopping the car's systems going to sleep properly

 

I used a (wrapped) razor blade to hold the plunger in such that I could lower the hood.

Initial reading was about -4 amps, similar to last time.

Waiting about 30 minutes, and checking again being careful to not wake the car up, the reading was -0.7 amp, which eventually reduced to +0.1 amp. I consider both of these to be within the error range of the zero/rel function, so it was basically zero IMHO. I'm sure there is always a slight drain but this meter isn't good enough to reliably measure it.

Opened the rear hatch to get the charging cable, and when I got back it was -2.1 amps again. I take this to mean the car was in a semi-awake state.

Plugged in the charge cable, no appreciable change upon opening the charge door and plugging in.

Initiated timer-override to charge, current briefly spiked to -15 amps then went to +7 amps over a few seconds.

So yes, it seems there is a period ~30 minutes or less where the car is drawing not insignificant amounts of power of the 12V battery, after which it drops to very little power consumed. I need to check one last thing: how much power it draws while waiting to charge on timer, after waiting to see if the car goes to sleep.

 

Tool worker as you suspect your 12V battery is fried. Your experience mimics mine almost exactly, I was experiencing pretty much monthly dead batteries until the summer when the low voltage was finally affecting the car even while driving. My dealer finally gave me a new battery 6 months after I took delivery of the new Kona and I have yet to jump start my car in the past 4 months. That is a personal best