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Issues with the 12V auxiliary battery


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My vehicle is now 2.5 years old, and I had my first issue with the auxiliary battery last April when it was 1.75 years old. I was working outside, and the car was left unlocked and open for many hours while turned off, resulting in the auxiliary battery being depleted to the extent that the vehicle would not start. I borrowed a charger, which provided sufficient power to the battery, allowing me to go, and I believed the battery was only depleted by the inside lights. During my midsummer service, I requested Kia to inspect the battery; they said it was functioning OK.
Everything was satisfactory for many months; nevertheless, there was another instance when the automobile was left unlocked for a few hours while I worked in proximity, however I ensured the doors were closed to minimise discharge from the inside lights. It failed to boot once again. I attempted a trickle charge for some time, but to no avail. Fortunately, a kind Mitsubishi PHEV owner and neighbour expressed interest and offered me his booster battery. This was not successful first, so I had lunch and attempted it again a few hours later. I presented him with a bottle of wine and purchased my own booster, which I have had to use many times lately when the vehicle was left unattended for about an hour without any doors being opened.

After providing the extensive information, I am attempting to determine if there is a component depleting the auxiliary battery fast when the vehicle is unlocked, or whether a new battery is necessary. - 2 A battery dying after 1 to 2 years seems premature. The vehicle is unmodified; I have not installed any other components, save from a USB drive with MP3 files, which likely consumes little power.

Today, I received a warning on the instruments indicating "check 12V battery."

Do you have any opinions? Thank you.

*It is peculiar that the vehicle is likely left unlocked and open for an extended duration for servicing; so, why did Kia fail to address the issue?

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If the automobile is unlocked, the 12V side is operational.

If the drive battery falls below 20%, the Battery Management System (BMS) will not activate to replenish the 12V system.

If you leave the vehicle unlocked for any duration, activate utility mode to ensure the 12V system is charged by the driving battery.

To be honest. If you have had a few instances with a depleted battery. It is time to replace it with a fresh one. As a unit, they have been depleted, potentially causing battery damage, and frigid temperatures are detrimental.

To assess battery drain, use a BM2 or BM6 Bluetooth battery monitor, which will provide an indication of any depletion.

An example of the battery meter on my e-Niro was last used on Saturday, January 4th. Remained snowbound till just today, January 6th. The 12V side saw a significant dip until the BMS restored it on 05-01. Subsequently, it declined once again overnight owing to frigid temperatures.

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Thank you both; it seems that a replacement is necessary, since the voltage is sometimes alarmingly low (below 6V). Thank you for the further information; I will explore the battery monitoring possibilities.

It is unfortunate that I need the automobile today; I must resolve this matter urgently, but that is life.

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Your 12v battery is probably functioning properly; the BMS activates when the terminal voltage falls below 9 volts (at least this is true for my battery). It is improbable that a few interior lights would induce the issue; they normally consume a little fraction of an amp apiece (about 0.1 to 0.2), hence the battery should be capable of sustaining this load for an extended duration. I have already discussed this, but my vehicle has had this issue seven times in over four years, always occurring in areas with weak mobile phone reception and almost definitely during attempts to do a system update. This diagnosis was suggested by an AA recovery technician, who came to assist me. He indicated that he had encountered this issue frequently and believed it to be the most probable cause. This reasoning resonated with me, as the problem consistently occurred in areas with poor signal, regardless of whether the car was open, closed, locked, or unlocked. Being locked was perhaps the most inconvenient. Best of luck; however, I advise against investing on a new batteries and recommend acquiring a few booster packs instead.

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However, I had already departed and replaced the battery. I saw a rapid decline in battery voltage, which was occurring with increasing frequency. We must observe the progression of events. It seems to have occurred in many areas with strong cellular service, therefore I am uncertain; I would not anticipate the system upgrade to be very power-intensive......It appears that incidents have consistently occurred when I have left the car unlocked or the doors ajar. While I concur that interior lights consume minimal current, my parents' Range Rover frequently experienced battery depletion due to leaving the boot open for their dogs, who preferred to remain in the back during the day, likely to avoid being left alone at home. I believe the interior lights are filament lamps.

I own a booster that has functioned well on many occasions; nevertheless, this morning, after using it to start the vehicle, I had issues upon disconnection, including a flickering display and a 12V battery alert.

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I believe KIA 12-volt batteries are subpar. Numerous problems have arisen with them (including ours) within a few years for both ICE and EV models, thus it is prudent that you acquired a new one. Additionally, ensure that you use utility mode if the doors are left open.

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