Is battery disconnection a problem?

[panason1c]

After reading of various problems on this message board i am wary of disconnecting the battery on my ML 270cdi (for whatever reason) as it seems that some posters have experienced problems when reconnecting, an srs light staying on after re-connection, for example.

Is it ok to disconnect, say to change batteries, or are there any precautions to take before disconnection to ensure there will be no problems after re-connection (apart from being in possesion of a radio code)?

 

[Martin Bell]

ECU Reset

The ecu on some MBs can be cleared of random glitches & fault codes such as SRS light on by MB Dealer Diagonostic tester or for DIY:-
Disconnect battery for about 30 Mins, after which re-connect switch on ignition for 10 seconds. Then turn it off again for a further 10 seconds, and then on again for another 10, at which point the engine can be started. Avoid the tenptation to touch the accelerator pedal once the engine fires, especilly if the idle seems low. Keep cranking & wait for the control unit to lift the idle speed to the point where you feel its safe to release the ignition key. Let the engine idle until it gets hot & then swith off. Restart & test all is ok.

 

[panason1c]

Thanks Martin.........So if i was doing a job on my ML that required me to disconnect the battery and then experienced problems on re-connection it would then be a matter of going through the above procedure that you have described.
Thanks

 

[philharve]

ECU with non-volatile memory

Martin

I assume the ECU in M-Bs vehicles either has a backup battery to retain settings in its memory OR it uses some form of non-volatile memory?

Is the procedure you describe above applicable to ALL M-B cars or just some?

Can you safely charge the car battery with an external charger whilst it's still in the car and still connected? I am assuming there is plenty of ventilation in the boot to prevent the build-up of potentially harmful gases. Would external charging harm the ECU?

REGARDS Phil

 

[tom7035]

I've always been led to believe that, since the introduction of alternators as opposed to dynamos batteries should always be disconnected before charging in the car (from an external source) to avoid possible alternator damage. These days of course this procedure may be outdated but I still follow it out of habit I suppose.

ECU's are something else altogether and all this modern electronic wizardry terrifies me!

 

[SLinKyjoe]

i am of the opinion that you can charge the battery with it connected providing your charger pumps out 4amps or less.

you are meant to disconnect it should you use one of them nuclear powered booster jump starter box things.

I could be wrong but the new slk works fine after a bout of chargeing whilst connected. I know its new but i managed to leave the lights on. in my own garage!!!!

i await a more knowlegable reply

 

[pascal]

Think I read somewhere 'bout a device to connect to the terminals whilst disconecting battery, but it was not necessary for MBs.

If you are that worried about it, you could always connect a 12V dry cell to the terminals before removal.