TCubed said:

Hi Chaps,

I managed to find the original spec list for the P38 (not sure how I wandered onto that part of the interweb) and it gives the alternator as 150A.

Now.. What is the diesel model of the car doing just after start-up to be using that much current so as to drain the battery on short trips??? I'd understand petrol with the spark, but I don't get diesel.

Just something of interest haha

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Saint.V8 said:

It takes a horrendous amount of power to start an engine.....think of the Cold Cranking Amps the battery can deliver....hundreds of Amps.....The Alternator has to top the battery back up again....short trips will kill a battery that is getting on a bit, and whilst without any other electrical services running, the Diesel still requires Battery to run the ECUs, Pumps etc.....still a good fe wamps worth + what it needs to do to recharge the battery....

The Alternator does far more work than people grant it for.

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Nickpen said:

When a car is running all the power to work stuff comes from the alternator, 2 blower motors for the heating system, 2 cooling fans on the rads up front, 2 heated screens, 2 heated seats, ABS pumps EAS compressor, headlights, all the various ecus, and its got to recharge the battery as well. 150 amp just about covers it. Diesels take some battery power to start, first you hit the battery with the glow plugs then actually cranking the engine, which it has to at a reasonable speed to get it going.
Short trips at this time of year with lights and heating on and its no wonder the battery dies

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