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MG MGB Technical - alternator

in winter, i have,in the past,connected my battery charger to the battery to aid in morning starts in freezing weather.
will this procedure damage the alternator ?
thanks for your comments.

Hi John.

This isn't recommended practice.

I understand that the theory is that voltage spikes from the charger could damage the semiconductors in the alternator (particularly when connecting / disconnecting), although if you connect directly to the battery the battery will tend to 'soak up' any spikes that do occur.

I seem to recall reading that some modern chargers are designed to avoid the spike problem.

Trickle charging overnight from a low-current charger is a better option in my view as it tops up the battery and warms it a little, both of which help with the morning start.
It is also worthwhile switching off all electrical loads (lights, etc) and running the engine at a brisk tickover for 30 seconds when you arrive at your destination.


IMHO there is almost no chance of spikes from the charger affecting the alternator *if you connect the charger direct to the battery*, which is where chargers are usually connected, due to its inherent smoothing characteristics. But connecting it to the brown at the alternator itself might carry a small risk, particularly if you got it the wrong way round.

However with the concealed battery in the MGB it is much more convenient to fit a cigar lighter plug to the leads of your charger, and also quite safe. If you have a choice get an unfused plug (the cigar lighter in yours was fused from the factory) as they can get a bit warm in use.
Paul Hunt

This thread was discussed between 20/11/2004 and 21/11/2004

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