Confused with MHEV battery - trickle charge/jump start
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Joined: Feb 2025
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Confused with MHEV battery - trickle charge/jump start
So there is a battery terminal in the engine bay on passenger side - the voltage is 12V. Is it a direct connection to the AGM battery in the trunk?
However, if it is, then how it's connected to the 48V battery? From reading the manual, this terminal is also for jump start, but isn't the 48V responsible for starting the engine?
However, if it is, then how it's connected to the 48V battery? From reading the manual, this terminal is also for jump start, but isn't the 48V responsible for starting the engine?
Member
Joined: Feb 2021
Posts: 116
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From: Australia
W213 e300 MY19 (Aus market)
My salesman at the dealership explained it this way: those terminals are the ones to use for jump leads and trickle chargers instead of connecting directly to the 12v AGM battery. This is done for electrical safety; ie prevent damage from arcing, or mishandling by people who may not be aware how to do it properly. I believe the owners manual says it is to protect the 48v electrical system from getting damaged.
either way it’s a 12v input to the 12v battery. The car has its 48v capacitor, converts the 12v to 48v and powers the drivetrain components, etc on 48v. I believe my car has the older 48v belt driver starter alternator, 48v water pump and 48v ac compressor. Whereas yours has the 48v integrated starter generator, 48v ac compressor and 48v water pump, etc.
either way it’s a 12v input to the 12v battery. The car has its 48v capacitor, converts the 12v to 48v and powers the drivetrain components, etc on 48v. I believe my car has the older 48v belt driver starter alternator, 48v water pump and 48v ac compressor. Whereas yours has the 48v integrated starter generator, 48v ac compressor and 48v water pump, etc.
