Is it allowed to separately charge the 12V battery in an electric car?

[George]

Dear Battery Doctor,

I would like to ask for your advice regarding the following issue:

Lately, my car (Kia Niro PHEV, 2022) has frequently displayed the following message after being parked for two days: "12V battery protection activated during parking." I have encountered this message before, even in warmer weather, but only after a longer period of inactivity.

The battery is 3 years old and has covered 40,000 miles.

My question is: Is it advisable, and does it make sense to occasionally charge the battery with an external charger? If so, should I disconnect the terminal before charging?

From what I understand, the battery is scheduled for replacement every three years. However, the owner's manual explicitly states that the battery should not be charged while the terminals are connected. Is this correct?

I appreciate your response in advance!

Best regards,
George

 

[Car Doctor]

Dear George,

The message "12V battery protection activated" is not an error message but rather an informational notification. It may indicate that the 12V battery is aging, but it could also be triggered by increased power consumption due to an OBD-II scanner, an aftermarket alarm or anti-theft system, or other modifications. In cold weather, especially below -5°C, this message is quite common since lead-acid batteries are highly sensitive to low temperatures.

If the message appears frequently even in warmer weather, I would first check the date code on the 12V battery. If it is older than 3-4 years, I would replace it without hesitation. If the issue persists, a service center can measure the car’s resting power consumption. In one case, for example, a faulty trunk switch caused the trunk light to stay on continuously, draining the battery. So, there’s no need to assume a major issue right away.

I do not recommend externally charging the 12V battery in an electric vehicle. The DC/DC converter is designed to maintain the 12V battery's charge while the car is active and sometimes even engages at random times, like 2 AM or 2 PM, if needed. The reason for the manufacturer's warning against charging the battery while connected is likely because reverse polarity jump-starting or incorrect charging can damage the DC/DC converter. From a technical standpoint, I don’t see any other reason for this restriction.

Best regards,
Best,
Battery Doctor

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