"Jon Elson" wrote in message
...
wrote:
The reason they won't charge a dead battery is the "polarity
protection" circuit to prevent hooking the charger up backwards and
doing damage to either the charger, the battery, or both.
Right, but if you are out in the woods with a dead car battery,
you need it to pump a little current into the battery to start the
voltage rising. If you get the load that drained the battery
turned off, and put a couple hundred mA into it, it won't hurt
anything. if the polarity is indeed wrong, the alternator diodes
will keep it from rising above about 1.4 V. If the polarity
is right, the voltage will keep rising, and eventually the charger
will decide to let you have rated current into the battery.
Jon
If you are out in the woods with a dead car battery the limitations
of an automatic charger don't matter. Revive the battery with another
vehicle or a portable jump starter.
jsw