Originally Posted by windrider
A shorted cell would cause increased current flow, thus tricking the charger in to thinking it needed to produce more current and voltage to charge the battery faster. Thus the converter would produce a high voltage and wait for the voltage to drop before it started to reduce current. That would explain the fan running all the time, producing high current constantly. It is all in the electronic brains of the converter.
Only if it was brain-dead enough to produce too high a voltage.
A good quality charger is BOTH current and voltage limited.
And not tricked so easily. Agreed that a shorted cell that
lowers the internal impedance and terminal voltage of the
battery can confuse SOME chargers. A truly "smart" charger
will switch off the charge current regularly and measure
the terminal voltage. Finding terminal voltage too low (shorted
cell) would cause the charger to quit and light a fault indicator......
But sounds more likely (to me) that the pass transistor in
the charger was stuck in in it's lowest impedance mode,
causing the max voltage the charger can produce to be
output. This can happen due to several single point failure
modes - shorted pass transistor, defective voltage sense
circuit, other failure points depending on type of
charger - linear or switching mode. Have experienced all
of these kind of failures at one time or another............
Still a very good reason to suspect the charger; the smell
of fish hangs heavily in the air. Unfortunately, the boiling
may well mean that the battery is toast, regardless of
original fault. Ouch.