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Discussion Starter · #1 ·
Up until a few days ago I'd never had a 12V issue.
Tried to start in the morning and nothing. Started it with lithium pack, and when it came on, it showed the boot was unlatched - this has been reported a few times by others as the cause.

I later remembered that a long while ago I'd installed a logger when I was investigating the top-up strategy.
The log results are rather interesting. Car was turned off about 4PM the previous day.

Seems like top-ups don't happen when the boot is open, as expected - presumably car not going to sleep.
But there are a three instances over an hour apart where there is a sudden large drop, the last being the terminal dive below 6V, but voltage is almost completely flat inbetween. The first two have a very similar duration and recovery shape, so I suspect the same cause for all three.
The voltage was virtually constant in the time before these drops, so doesn't seem they were triggered by falling voltage.

The car does not have telematics, scheduled charging was enabled ( but charger not plugged in), though schedule times ( 1230-430) don't coincide with these events- the first is 2.5 hours before schedule start, the second 1.5 hours after.
I subsequently tested the battery with a ~24A load, and it dropped from 12.3 to about 11.8v and held fairly stable for a few tens of seconds before my load got too hot. Battery is about 2.5 years old.

I'm not too familiar with lead-acid characteristics, but the discharge curves I've seen all show at least some voltage drop with decreasing state of charge, so it looks like the draw most of the time is pretty low until that big load turns on, and at some point the battery's internal resistance is too high, causing a death-spiral, maybe due to a switching regulator somewhere increasing its current draw as the voltage decreases.

I think I'll have to add current monitoring to try to get a better handle on what's happenning.


146248
 

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Kona 64
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Sorry you have now succumbed and out of warranty. It will interesting to see if your battery can still hold a charge overnight. I suspect that if it fails again you will need a new battery.
Mine failed at 15 months, boot lid left unlatched by the garage. I now have a conditioning charger and charge it slowly once a month. I do not have a logger so can not visualise whether this is doing any good.
 

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@mikeselectricstuff , yes you maqy need a new battery if it doesn't hold charge well.

It would be interesting to know if you get 4 hourly 12v top ups when everythig is properly closed??
I now think I may have broken car :( I'm on 3rd battery already.
With the latest software I do get top-ups every 4hrs. But then there are days where not a single top-up is recorded by my BM2 for several days. The car is driven on those days but nothing happens while the car is parked overninght. And several days later the charge schedule comes back. Then it disappears for a few days again.
 

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If my 2nd battery (now 18 months old) fails and its now out of warranty I will,

1. buy a better quality battery, probably AGM deep cycle if I can find one that fits.
and
2. get one with a good warranty.
But as things stand my 2nd battery is 18 months old and behaving I must be doing something right whatever that might be.
 

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Any idea what that big load might be, @mikeselectricstuff ?

Seems like a heck of a big load to cause the voltage to drop that quickly, and given that your load test resistor got very hot pretty quickly it's reasonable to guess that whatever is causing that voltage drop is also getting pretty hot. I think that would probably bother me more than whether there has been damage to the 12 V battery, TBH.
 

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Discussion Starter · #6 ·
I just ordered a current probe to investigate further, as it's hard to infer what's actually going on with just voltage.
It could be that the load isn't actually that big, but the battery's internal impedance was just increasing as it was discharging.
I'm surprised that it would discharge so far with virtually no change in terminal voltage, but I know lead acid can be a bit weird sometimes.
 

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I’m awaiting my Kona but keep hearing about this boot problem… does the car still lock normally in these circumstances? And if so, is there no way to just disable the sensor somehow? (I’m assuming it’s going to be a simple open closed circuit with something like a magnetic/push switch). I’d rather give the boot lid an extra tug to check it’s locked then worry about 12v drain
 

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Discussion Starter · #8 ·
Yes it still locks OK. Not sure how practical disabling the sensor would be as it may use it as part of the unlocking sequence - i.e. it may keep retrying to unlock if it thinks it's still locked.
I don't think it's that big a deal - first time I've done it in 2 years.
I would however say that carrying a jumpstart pack is absolutely essential as it means it's not a big inconvenience if it does happen - couple of minutes vs. calling recovery
 

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Yes it still locks OK. Not sure how practical disabling the sensor would be as it may use it as part of the unlocking sequence - i.e. it may keep retrying to unlock if it thinks it's still locked.
I don't think it's that big a deal - first time I've done it in 2 years.
I would however say that carrying a jumpstart pack is absolutely essential as it means it's not a big inconvenience if it does happen - couple of minutes vs. calling recovery
Brilliant thanks. Seems crazy that a new car you need to take precautions like that. I’ll grab one to keep in the glove box, fingers crossed it’s never needed!
 

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EU base model with heat pump Sept '18
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I’m awaiting my Kona but keep hearing about this boot problem… does the car still lock normally in these circumstances?
The vast majority of owners don't have any problems with the boot but it pays to wind in the two rubber bumpers as soon as you take delivery. Just look at it when you get the car.
 

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The vast majority of owners don't have any problems with the boot but it pays to wind in the two rubber bumpers as soon as you take delivery. Just look at it when you get the car.
Thanks, I’ll wind them in and see how it goes. I’m excited for the car, the wait is killing me though! I need to stop reading all the “issues” lol! I only came across this 12v one cause it’s my first brand new car so wanted to hardwire a Dashcam to record 24/7 (where I’m charging it’s far more convenient nose out, but that leaves the risk of people walking past in the evening attempting to unplug :-( the world we live in where you can’t trust people…)
 

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on pickup I asked if they could adjust the boot to ensure it shut okay, the handover person seemed a bit confused by this ( which I assume is same for BEV, PHEV, Hybrid models regardless ).
It then took him 3 goes to shut it
He went off to ask someone else who came back and twiddled to success
 

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I’m awaiting my Kona but keep hearing about this boot problem… does the car still lock normally in these circumstances? And if so, is there no way to just disable the sensor somehow? (I’m assuming it’s going to be a simple open closed circuit with something like a magnetic/push switch). I’d rather give the boot lid an extra tug to check it’s locked then worry about 12v drain
Once you are aware you can judge by the ‘clunk’ as to whether you have closed it correctly. You get a less than adequate clunk when its not quite shut. Its easier when you shut the boot and then get in the car as you get an open boot warning on the dash.
If you do not shut it properly the shut lines look like those on a Tesla, haha.

I have had no issues since the dealer failed to close it properly after a service 18 months ago. .
 

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... but that leaves the risk of people walking past in the evening attempting to unplug ...
If you ensure that the Auto button on the kick panel (near right knee) is "off", indicator light unlit, the plug will remain locked after charging completes until you unlock the doors. Even then you only have about 15 sec to remove it.

With Auto "on" it's unlocked whenever it's not charging.
 

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I think I'll have to add current monitoring to try to get a better handle on what's happening.
It's highly-concerning how quickly the 12V battery failed to support the load. Two of us owners have also recorded that the ABS events fail when the boot is open.

Mine, boot left open intentionally for just an hour:
146332


Navguy12, boot left open accidentally overnight:
146333
 

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All very interesting. Does the same thing happen with other doors not properly shut or is this unique to the boot?
 

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All very interesting. Does the same thing happen with other doors not properly shut or is this unique to the boot?
Almost certainly, but that's a much harder mistake to make. The boot is annoyingly vague in comparison.
 

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On the LEAF it's impossible to lock the car with a door/boot not properly shut - the car just beeps annoyingly at you. Does the Kona appear to lock normally in this scenario or is this only happening with the car unlocked?
 

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Not sure from my experience. If the car is locked and I open the boot by the handle with key in pocket it's possible to misclose it without any complaint from the car. The closing noise is subtly different and it jiggles if subsequently checked. Some owners might not notice any of this.
 

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Batteries seem to accelerate in discharge volts because some cells go beyond flat, and start charging up in the opposite direction.

Once that has happened, the battery is ready for the tip, as it will be seriously damaged.
 
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