12v battery replacement

Tyanks for the pics..Looks good. The AGM battery seems to work fine, but it looks like my charging system is hosed.
I get a red "charger" icon when I connect the charger, and will not charge. I probably screwed it up when I was trying to charge the car with the 12v bqttery dead. Connected an external battery charger to try to get it to charge, anD i think that caused some problem.
Tried the 30 second on, 4 hours off with all doors locked as recommended bY Kiwi, but still having trouble,.
The car indicates a problem with the el3ctrical system upon starting, but driveable. Regen braking works.
I will try the reset method again: disconnect batttery, reconnect, turn car on for 30 seconds, turn it off lock doors and wait 4 hours (actually I wll let is sit ovenite).

 

The Kona is going back to the dealer. I am putting back the dead Rocket battery, and jumping the car to get it there.
I would love to leave the AGM battery in it, to avoid them replacing the Rocket as their first step but I cannot help thinking they may pin the charger failure on me saying that me replacing the 12v with an AGm caused the charging subsystem failure.
I know, that is paranoid thinking...

 

There's certainly no need to take a chance if that can be easily avoided.

 

Tried to charge it this morning, and.. it is charging now, kind of.
Tried the Granny charger 1st, that worked, then plugged in my Level 2 ChargePoint charger, and it seemed to be charging with that as well. The red "charger icon" on the dash is actually OK, it just indicates that the charger cable is connected. In the excitement, I mistook that for an error indication. The ChargePoint's status indicator flashes blue, which means it is charging the car, and the Kona displays the charge rate and the expected time it will take to complete the charge.

Did charge for a bit, went from 75% to 77% but then it stopped. I reckon still going to the dealer.

 

Do you have your charge set to %100% or only %80% if its only 80 and it only charges to %77% its probably you have %3% battery decay,
so perhaps if this is so set charge to %100% and se if it charges to %97% if so all good

 

That phenomenon has not been reported by anyone else with an SoH lower than 100%.
Pretty sure @coder is still at 100.

 

My propulsion battery has been recently replaced, it looks 100 %. Usually I charge to 90 %, but now I have it set to 100 since the 12v battery troubles started.
The charge attempts took place at 75% ( charged up to 77% and stopped, then a bit later tried again, charged for a bit and stopped again in 15 minutes.
I am looking through my logs for my Chargepoint level 2 charger, and from that point of view these look like normal charging sessions. The charger does not report any error.
In any case I put back the Rocket battery, and dropped the car off at the dealer. I will post if anything new emerges.

 

Argh.. heard back from the dealer. They run diagnostics, and decided that the propulsion battery needs to be replaced again. They claim the first code was something like "12v battery abnormal" , but runing further diags pointed them to the HV battery, and after consulting with HMC they concluded the 12v battery failure was somehow caused by the HV battery. i would love to be a fly on the wall for that troubleshooting session. Asked them about the 12v, and they said if there is any problem with it, after the HV battery
is replaced they swap it out for me under warranty, because "clearly the 12v battery failure, if any was caused by the warrantied HV battery failure". Makes zero sense to me, but I am not going to argue with them.
Prior to taking the car to the dealer, I took out and charged the Rocket 12v on my Shop charger 2x1 hour, at 40 amps. I have charged it before, and i notice it needed 2 sessions, otherwise it would not hold the charge at all. I could see its voltage dropping as i had my voltmeter on it. At that pointthe battery was in the car, so maybe the car had some internal short.

While at the dealer overnite, it apparently hold the charge enough that they could drive it
in the morning. Maybe charging it on my shop charger several times managed to de-sufate it.

 

You could always drop off the AGM you bought and have that 'officially' installed when the new traction battery arrives.

 

I think i keep the AGm around, and when the flooded battery they use now inevitably dies, I replace it with the AGM. I dont want to push my luck with the dealer, they do not seem to have a clue. I think they would just get confused being asked to install a non-approved battery. I have not seen to much evidence of cognition there, they just pull the diagnostic codes using their proprietary diagnostic tool, and send those to Korea for interpretation.

When it suits me, I just play dumb. If the batery replacement takes too long, I may sue them and get some money. At this point, the car is not a life or death thing, just a convenience. We have enough cars in the family to get by.
In retrospect, imo the current wet Lithium battery technology has too many problems.
The next gen solid state batteries will solve all that.

 

The dealer has replaced my HV battery. It only took something like a week and a half.
HMC is probably stocking replacement batteries in US warehouses now.
Anyhow, the dying Rocket (original) 12v battery miraculously recovered. Before taking the car to the dealer, I took it out of the car and charged it on my shop charger. Maybe I managed the de-sulphate it. I was charging it alternating the AMP settings between 5,10 and 40 amps, so who knows.

They told me the HV battery failure caused all the 12v battery problems, maybe it caused a rapid internal drain, who knows. I am going to put the BM2 on it and see if I can assess it better. In an case I have tghe AC DELCO AGM ready to go if needed.

 

Lots of BMS activity (which is part of the traction battery) like cell balancing could drain the 12V battery as some or all of that is done with the traction battery offline.

 

I am monitoring the 5 year old OEM Rocket battery with MB2 now. It seems to be topped off on a regular 4 hour schedule. Immediately after the 20 min charging session there is always a small dip in the voltage, then it settles at 12.85. By the end of the 4 hour period it drops to 12.78 -12.80, and it repeats. so it looks healthy to me. Trying to decide if I should swap it with and Ac delco AGM. I am unsure why the 12v batty recovered in this way, before it would be at 4-5v with the car dead.
I took a look at Kiwi-s posted charge graphs, and I notice one difference. My charge cycles always features a few minute of dip in the 12v battery voltage, then it comes back up to what I would expect after just having completed a charging. Kiwi-s graps does not have this dip. I wonder it the presence of this indicates a problem with my battery?

 

It may have been damaged, but obviously not much if the charge holds at 12.8 (100% SOC). Having said that, it may no longer have full capacity, but you won't really know for sure unless you apply a heavy load to it. I would just leave it and keep monitoring it with the BM2.

If batteries get discharged but immediately soon after charged to full, damage may be minimal esp if it is a higher quality battery. However, if it doesn't not get fully charged, and/or repeatedly gets fully discharged, damage (sulfation and stratification) is more likely. That is more common in ICE cars that are driven infrequently and only short trips. They don't get recharged by a traction battery every 4 hours.

 

Sounds good... what should I be looking for in my BM2 logs to indicate that I should swap out the the current battery? (The Rocket). I guess I could have it tested at autozone. I had that done when it was apparently failing, and they told me it was toast.

The only thing that makes sense to me, that somehow, during the multiple out-of-car charge sessions it got desulfated.

 

There are some chargers that can desulfate a bad battery if it is not too far gone.

If it starts dropping further between charges, that would be a sign. But if you are holding at 12.8V, that is actually exceptionally high. Neither of my BEVs are that high, but I don't consider the batteries to be going bad, as they seem very consistent with their gradual discharges and charges.

I don't trust some of the battery shops (although most are OK), as they might just be trying to sell batteries. I have my own tester, which can does a load test as well. Have been using it on all my past cars when the battery starts getting weak, so have a pretty good idea what is good or not.

I had a 2018 Crosstrek (bought in fall of 2017) that I passed on to my grandson last year. It still has the original OEM battery (with a BM2) and is still good after 6.5 years. Those are the ones that usually don't last more than 5 years. What hurts batteries too, is in high heat environments (like AZ). It is very important to check fluid levels and top them up with water as required. But it is the cold winter weather that usually exposes a weak battery, necessitating a replacement. Slow cranking is a sure sign.

 

Those voltages at face value look fine. However the dips are another question.

When the car is awakened for a 12V charge the 12V battery must support the LDC unit (converts HV to ~12V) for one or two seconds before and after the LDC starts supporting the 12V system. The magnitude of the dip at the end of the event would certainly reflect the resiliency of the 12V battery to handle the transition. I've seen in some cases where the settled voltage is lower after a 12V battery charge and wonder what the point of it was.

As an aside, note that the BM2 logging function only samples every 2 minutes so it may or may not always catch the resulting dips in the system voltage. If you monitor it live I believe it samples every 1 second.

I would say that it does. But even when in good condition the Rocket is barely adequate to do the job intended. I think Hyundai/Kia did not size the battery to cover a high enough percentage of use cases. It would be adequate only if the car could quickly detect and support a depleted battery, essentially how Tesla fixed the same problem with their tiny LFE auxiliary battery. The gen-2 Kona/Niro have more capacity, I think 60Ah over 45.

I'd suggest installing the AGM and keep the Rocket as a garage ornament. Mine is sitting here next to me in the kitchen and I charge it once a week just like the car did, at 14.7 V for 20 minutes. I may use it when the car goes into the dealer for the annual inspection.

 

My Kona Rocket is at 5 years in a couple of weeks, and exhibits the same numbers: between 4hr charges is at about 12.8v+, at the end of a charge briefly drops to 12.65v then resumes, a short outing causes dips to 12.25-12.3v at each ignition off, followed usually by a 4x30min charge cycle but sometimes followed by 2hr at 12.6v instead, then back to 12.8+ 4hourly. The only difference is that I have not had a Rocket failure.
I’m not convinced I need to do anything immediate, primarily because when I look back to my earliest data (June ‘22), all the numbers and pattern were just the same then. But I haven’t bought a replacement as you have already - you might as well install it, check all is OK, then forget about the problem..

 

Thanks for the awesome replies!
Kiwi, if I am reading your post correctly, the initial load of running the LDC unit causes my brief dip in voltage, This by itself indicates that my OEM battery is weak. The dip is maybe 0.4 volts and quickly recovers once charging starts.So the initial running of the LDC acts like a brief load test….
But on your charts, we do not see thiis dip.

(Irrationally) I am a bit hesitant replacing the battery now, since (coincidentally) the HV battery failed after I did it the last time. Maybe it did not like me supporting the voltage with a shop charger while trying to charge the HV battery. The car did something weird at that time, flashed the lights a few times and beeped the horn, and locked itself. Started displaying the “check electrical system” warning after that.
It is hard to infer anything from limited data, I do not know if it was coincidence or causality.
I can now let the car sit unused for days, and the 12v battery does not die, like it used to before the recent HV battery replacement so I am thinking let sleeping dogs lie.

 

Saw my first 'dip' today at the start of charging, so I'm not immune!