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mm

On 15 Dec 2006 18:55:15 -0800, wrote:

Dave Plowman (News) wrote:
In article ,
Jim Land wrote:

"An abrupt reduction in the alternator load causes a positive voltage
transient called "load dump." In a load dump transient the line voltage
rises to 20V or 30V in a few microseconds, then decays exponentially
with a time constant of about 100 microseconds. Much higher peak
voltages and longer decay times have also been reported. "The worst
case load dump is caused by disconnecting a low battery from the
alternator circuit while the alternator is running. Normally, this
would happen intermittently when the battery terminal connections are
defective. "Load Dump transients also occur when heavy loads are
switched off, although their magnitude and duration will be lower.
These transients are capable of destroying semiconductors on the first
'fault event'."

Given the number of semiconductors in use in the average vehicle - and
have been since the first transistor radio - it seems to be a problem that
has been solved...

Yes. However a resistive dropper does not solve it, nor does a simple
volt reg. A 12v vehicle system load dump onto a 6v tv would be a setup
waiting to fail.

Well, I think I could totally solve this problem by not running the
engine when I'm watching tv. I wasn't planning on actually driving
and watching tv, a fully charged battery should last a long time at
only 1.6 watts. Plus I have a Battery Buddy that disconnects my
battery when it is getting pretty low, while leaving enough to start
the car. It works great.

If the OP is incautious enough to do this, it should survive longer if
you never switch heavy loads on or off while the tv's connected. The
heaviest of course being the starter motor.

But I won't be starting the car, nor running the heater fan, or
anything more than the courtesy lights.

NT

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