Will this work?

[dry run]

So, time to change the battery. Not sure how many I've got, but the one under the bonnet is definitely not happy.

I'm keen not to "bu66er up" the memory settings seats/windows/radio etc. so will this work?

Connect a second battery to the charging posts under the bonnet
Disconnect the duff battery (mqaking sure to protect the terminals from touching anything)
Install new battery and reconnect terminals.
Disconnect battery from the charging posts.

Any advice gratefully recieved.

Cheers

Steve

 

[Blobcat]

Yes that will work, I’ve used the same method multiple times.

As you’ve said just be careful with the positive lead as your brain is telling you it’s disconnected as you’ve just taken it off the battery… it’s of course back fed from your battery on the charging post.

 

[rorywquin]

If your charger (e.g. like CTEK chargers) has a "power supply mode", that is exactly what it is for.

 

[dry run]

Thanks guys!

 

[Botus]

the radio will never know if you took the battery off or not - the only setting on modern cars is the window safety anti-trap thing, that always need the 5 second reset per window switch

the aggro and risk of muddling it up (following your suggestion) and doing an alternator or pre fuse board is huge,
you might even find the car thanks you for a 30 min disconnection as it boots up fresh and works as intended instead of a muddled mess

FYI worth thinking about - I wasn't aware Mercedes needed / benefited from the "Battery reset idea" (that is a well know fix on BMW's). But indeed twice recently after some intensive work, the car muddled its brain and forgot how to work. The gateway forgot how to do its job and blocked any comms to diagnostics.

A 10 min forget what you think you know. Just go to sleep and wake from your muddled hypnotic episode was completely sorted by disconnecting the rear battery. (if you must know flashing the OCP gets the 221 in a right mess - afterwards I vaguely remember one module needs the key out (it throws every possible error on the car round the network even using offical online dealer kit and clogs its brain forever more unless you go wipe the shadow memory), on this module its certainly not key on first click, nor key fully on, as is a must for the other 50 modules)