Charging a car battery with only very short trips

4 Jul 2007
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United Kingdom
In Charging a car battery by driving it most replies of course are about the battery and charging issues, but I see reason to think it might as well be something else.

On Sun Feb 11, 2007 6:37 pm (page 2) the "Topic Starter” (confusion not intended) writes:

That's what the AA man tells me when I have to call them out to start the car. Please don't get the idea I play on this by the way! The car is perfectly OK in the good dry weather. It'll sit for a month and start right away!

Don't get me wrong the last time it happened last May the battery was dud and they had to give me a new one under warranty, yet they had told me only two months previously it was perfectly OK.

Luckily I haven't had to call them out since then, but then again the battery is only 9 months old.

All of you are right that cars ought to be run for longer in order to serve the battery as well as it tries to serve you. Absolutely true.
That said, I would like to point out that I have seen old run-down vehicles being started for a run of less than a mile on weekend mornings and evenings only. Four starts and short runs per week, or less if the weather was too bad for flying. That was the old lorry on which a gliding winch was fitted. The winch installation had a separate engine and electrical system.
This clearly is bad for the engine and the battery – but it gave no starting problems. Same experience with the launch point bus or so that many gliding clubs have: 4 runs of half a mile per weekend, then 5 days idle in the hanger. Different drivers. Still no regular problems. If my memory serves me right.

Note that Topic Starter pappyon mentions that in good dry weather the car would start o.k. even after a month of non-use. As long as the weather is fine.
To me, that sounds like the battery is normally coping reasonably well with its nasty living conditions. Like the latest replacement one has already shown for 9 months.

If it plays up mainly in damp weather (as the problem owner appears to say): no spark in the right place?
If it starts often with difficulty or sometimes not at all in damp weather, could it be that the 12 year old high tension leads or the distributor cap are the real culprit? This is related to lots of moisture in the air. New leads, possibly also a new distributor cap (some cars are sensitive to this) and maybe also new spark plugs should take care of this.

On the other hand, if it plays up mainly in cold weather: not the proper amount of fuel in the right place?
It might well be trying to start on old summer petrol when it is mid-winter and would start much better on the proper winter petrol that evaporates significantly better to enable cold-soaked starts. Having the tank filled with the petrol that becomes available in the late fall (ask a petrol specialist) might do the trick.
First try to use (another good reason to do some extra driving!) or else take out most of the old summer petrol (donate to someone driving more often) and then add winter petrol bought at a busy service station.
This would be a low-temperature related problem. Through the kind actions of petrol suppliers, normal customers automatically always drive on the proper type of petrol in this respect. It could be clever not to fill up completely, otherwise you would start the summer with a lot of remaining winter fuel.
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