12v battery problems, causes and solutions

[Stuart Wright]

From our podcast 8th July 2024 where we discuss 12 volt battery problems, causes and solutions.



1. 12V BATTERY GOES DEAD

MG5 (FL) 12V Battery Drain
Dead 12V battery - any help and advice please?
12V Battery dead, how to charge?
MG4 battery always dead after holiday

PROBLEM: The 12V battery becomes discharged and the car is dead, so it doesn't respond to the key fob and cannot be woken up or driven.

CAUSES: There are several possible causes for this problem:
a) A Bad 12V battery that will not hold its charge - this needs to be replaced with a new one - modern 12V batteries are low quality and don't last many years. Leisure-style batteries are the best replacements although can be expensive.

b) The car isn't charging the 12V battery as it should - this usually requires software updates to rectify from the dealer.

c) The car has been left for an excessive period without being driven - if the car is laid up for more than 1 month, it is typically recommended that the 12V battery be disconnected to avoid discharge.

d) Parasitic drain - something is plugged in to the car (e.g. an OBD2 reader or Dashcam) that is draining the battery much faster than it should be.

FIXES:
a) Jump start the car with a portable 12V battery (many people carry these for just this circumstance), once woken up, the HV battery should then start charging the 12V battery and you should be able to drive ok.

b) Jump start the car with another car (e.g. ICE/EV or using the emergency services).

c) Replace the 12V battery with a new one that has been charged.

DISCUSSION POINTS:

• EVs don't care about cranking amps, they simply need a small 12V battery that is happy being gently discharged and charged over many many cycles.
• Note you must never use an EV to jump-start an ICE car, it could damage your car.

 

[John11000]

From our podcast 8th July 2024 where we discuss 12 volt battery problems, causes and solutions.



1. 12V BATTERY GOES DEAD

MG5 (FL) 12V Battery Drain
Dead 12V battery - any help and advice please?
12V Battery dead, how to charge?
MG4 battery always dead after holiday

PROBLEM: The 12V battery becomes discharged and the car is dead, so it doesn't respond to the key fob and cannot be woken up or driven.

CAUSES: There are several possible causes for this problem:
a) A Bad 12V battery that will not hold its charge - this needs to be replaced with a new one - modern 12V batteries are low quality and don't last many years. Leisure-style batteries are the best replacements although can be expensive.

b) The car isn't charging the 12V battery as it should - this usually requires software updates to rectify from the dealer.

c) The car has been left for an excessive period without being driven - if the car is laid up for more than 1 month, it is typically recommended that the 12V battery be disconnected to avoid discharge.

d) Parasitic drain - something is plugged in to the car (e.g. an OBD2 reader or Dashcam) that is draining the battery much faster than it should be.

FIXES:
a) Jump start the car with a portable 12V battery (many people carry these for just this circumstance), once woken up, the HV battery should then start charging the 12V battery and you should be able to drive ok.

b) Jump start the car with another car (e.g. ICE/EV or using the emergency services).

c) Replace the 12V battery with a new one that has been charged.

DISCUSSION POINTS:

• EVs don't care about cranking amps, they simply need a small 12V battery that is happy being gently discharged and charged over many many cycles.
• Note you must never use an EV to jump-start an ICE car, it could damage your car.

I carry a 12v jumper pack in case of battery failure. Today I needed it but where was it? In the boot which is virtually impossible to open if the 12v battery is dead. Take heed and keep it inside the main compartment not the boot.