12V battery

My Kona keeps regularly re-charging its 12V battery when on EVSE and high voltage battery charging session is completed.
I keep my car locked with all doors closed when charging.

 

Since the BMS updates in Fall of 2020 my car charges the 12 volt very, very frequently. Several times a day. In the first year of ownership it took me six months before I ever saw the light on the grill. Ever since I see it several times a day.

 

Have you noticed any correlation between use of the interior heater in Winter and your 12 v battery being discharged so much that your Kona Electric would not start without an external "jump start"?

My 2020 Kona Electric 12 v battery frequently died in the Winter (Dec 2020 and Jan 2021) after I had been using the heater. My 2021 Kona Electric did not have problems starting until I started using the heater in January 2022. The 12v heater probably draws the largest amount of current from the 12v battery. The DC to DC converter should keep the 12v battery topped off, but may not be keeping up when the heater is used.

 

My 2021 model charges the 12V battery frequently, like almost constantly, while the car is running. After it is shut down it continues to charge frequently, cycling every few minutes, but gradually settles into 20 minutes every 4 hours. If left long enough that 20 minute charge becomes less frequent. There's a thread on it somewhere here.

Unless I'm mistaken there is no 12V heater. As far as I understand it the resistive (PTC) heater is powered from the traction battery with its fan powered from the 12V battery. The DC-DC converter should be able to keep up with the fan while driving but what happens while it's charging is a different matter - of which we in mild climates have no experience.

 

When you run your heater, is the car actually “ready to drive”?

Reason I ask: it took a few weeks to get my wife to understand that when she would get into the car and just push the start button without her foot on the brake, it was only the 12 volt battery feeding juice to everything (even the HVAC fan). Having the car alive but not ready to drive will quickly drain the 12 volt battery.

 

Yes, mine gives me a warning.... I was fiddling about with the car in what would normally be ACC mode with a key, ie start button pushed with foot off the brake. The radio was on for a few minutes, then a message popped up warning against discharging the 12V battery.

 

Yep, that could be it. Just the load from some electronic systems, HVAC fan and main battery contacter would draw a fair amount of current off the 12V battery.

 

NEW 12-volt battery 4hr charging behaviour to be aware of / be wary of

My Kona HV battery was replaced on 1 June, plus software updates. The 12-volt charging regime continued 4-hourly as before.

On 17 July I went on a 170km trip, between 13:30 - 17:15 (shown below). SoC started at 60%, finished at 24%. Note there is no 4-hr charging for the rest of the day.



My home charging routine is built around 1 hour of free off-peak power I get every day from the supplier, so the Kona is always hooked up for a scheduled charge between 09:00-10:00. As I don’t use the car a lot, I decided to just let scheduled charging each day slowly build the SoC % back up to 60%. My power is prioritised for winter heating at present, so charging is at 15A, giving 4% SoC / day. The following jpeg shows 1 week of charging. The car wasn’t used on 3 days.



Apart from scheduled charging events and a couple of brief retail outings, there was no 4-hr 12v charging during this past week (above).

Today, after a week, the SoC level has advanced to 40% during the scheduled charge. And at 40%, 12v 4-hr charging has returned, as below..



My conclusion: at least under the latest BMS software, there are no 4-hourly, 12-volt battery top-ups if S0C is less than 40%, favouring the HV battery ahead of the 12-volt, so, a typical ice-car scenario.

Therefore, Kona EV owners who are prone to 12-v battery issues, should not put off re-charging if SoC gets low, but at least charge above 40% ASAP to ensure continuing BMS support..

 

So you have tested that if HV Battery SOC drops below 40% SOC, 12 V battery is not being topped up anymore?
Also i believe BMS has nothing to do with that. VCULDC module controls 12V battery charging/topups.

 

I wonder if manually charging the 12 v battery every 3 or 6 months would help extend the battery life

 

Battery replacement incl. software wasn't done by the dealer, but by Hyundai NZ at their head office site on 1 June. On 3 June the car had its annual service by the dealer, plus transfer case oil replacement. I would tend to believe all updates have been done..

 

True, I was told by the dealer in Napier long ago that the battery replacement program was being handled by the importer and that relevant BMS updates would be applied at that time. Still waiting for this, however ...

I might test the loss of 12V battery charging under 40% SoC on my older firmware. But I see that it still charges for 30 min at the start of each traction charging session and that there is evidence of activity subsequent to that which I've always assumed is a BMS maintenance function.

That would be far too long as the condition can change much more quickly. I use a 5W solar panel to keep my ICE battery fully charged when parked and it does work very well, even in winter, but it has no means of regulation and can exceed 15V at times so I have to keep an eye on it. During summer I'll either use a 1.5W panel instead or just turn over the 5W so it's facing the ground. The pic below is a mid-winter but sunny day.

 

I'd like to use a small solar panel of about this size to keep my Kona 12V battery charged. I've had problems with it in the past and my first 12V battery was only trustworthy for 2 years (but I kept it for 3 because I'm dumb.) There are two questions about this that I don't yet know the answers to:

1) Will using a small-wattage solar panel interfere with VCU(Vehicle Control Unit):LDC(Low voltage DC-DC Converter) work to keep the 12 V topped up?
2) How can I most inconspicuously connect the panel to the battery?

Any thoughts on that, KiwiME or anyone?

 

My Auckland dealer is also doing replacements - I’ve observed a truckload of new batteries arriving while picking up the car after the 3 June service.
Maybe give your dealer another prod..

 

The Kona will not care about this and will only know about the added charge if the ground connection from the solar panel is made to the chassis instead of the battery (-) terminal. I doubt it matters either way because it's not a lot of power.
The panels come with a disconnect plug that is not waterproof so needs to be tucked under something or covered. You'd also want to connect to the battery with proper terminals and a fuse for safety. You might find there is a kit for this. Also, the panel may be not weatherproof. I took mine apart and found that it's mostly good enough for direct rain but it won't hurt to silicone-up any gaps, etc.

 

Curiosity got the better of me and I was able to show that it happens as well on my early model, updated only as far as Campaign 196 several years back.

I'm becoming somewhat convinced that balancing is being carried out after traction battery charging because it's in good balance and I've haven't been over 80% in more than a year. The 12V sag of course is because the BMS has to read cell voltages as OCV, open-circuit voltage.

 

That’s a good confirmation, and across multiple BMS versions too - very useful!

I’ve seen that long-duration ”staircasing” for your 12v sag in your pics before - I don’t remember ever seeing that with my Kona, which typically are like the single spike at 9am/29July in your 1st pic. What do you attribute that to?

 

That spike is a 5 min drive and the one following is a 20 min drive.

We know that anytime the level is at 13.1 or 14.7 V the main contactor would be closed and powering the LDC to support the 12V systems without depleting the 12V battery. I can only assume that to carry out tests or balancing maintenance of the traction battery that contactor must be open and power for the BMS derived elsewhere, presumably from the 12V battery.