CL203 charging battery - real basic question

[stevebear]

Posted this in the Mercedes section earlier this morning but no reply. Heres hoping someone in GG can reply.....

Merc Sport Coupe - alternator appears gone for a burton - dash message about Low Voltage, turn off consumers so being looked at on Tuesday.

I would've thought battery should hold enough charge til Tuesday morning but to ensure I can get it the 3 miles down the road to the garage, is it ok to just connect up the leads from my charger to the battery with it in situ or should the battery come out?

Daft question I know but been years since had to charge a battery and the last vehicle I would've done this to was an '88 Escort. Not sure whats best these days when you've a car with more electrical gubbins.

Thanks folks

[littleredrooster]

I'm sure you'll get polarised responses to this - some will say yes, others will tell you it will cause nuclear holocaust, but I would be happy to top the battery up with a charger whilst in situ.

I would, however, wait 15 mins after turning the ignition off to ensure the ECU has fully shut down, then connect the leads before turning the charger on.

[ejenner]

Battery chargers do no more harm to the vehicle electronics than the alternator would.

If you use a particularly aggressive fast charger you could damage the battery but generally speaking any component designed to be fitted to a production car is going to be tough enough to cope with a variety of voltages / high currents / reverse polarity and these sorts of faults which could come up during the vehicles use and maintenance.

Which is better? Much better to do it with the battery disconnected as you're not wasting any energy powering circuits in the vehicle, not that there would be much draw while not using the car.

[blank]

Positive from charger to positive on battery.

Negative from charger to a good earth - unpainted bracket on engine or similar.

This is usually how cars are kept topped up when at the factory.