Hanz wrote in
:

Spikes: when the batteries goes from 11.75 up to 14.5 volts during
normal charging. Maybe 'spikes' is a bad word. But the "buck/boost
circuit" of the converter handle it.



I don't know of a single piece of marine electronics that won't run just
fine on 16-18VDC. "Spikes" are 40V pulses that happen when a battery
with a dead cell is charged with an alternator that happens each time the
alternator's regulator, trying to figure out why the battery's voltage is
only 9.8VDC and charging the hell out of it because it measures deep
discharged, feeds full field current to the alternator.

You can hear it in the stereo in a vehicle or boat as a loud, high
pitched and varying with engine speed, whining in the speakers. You can
also see it in any light as you rev the engine and the light gets MUCH
brighter, the light bulb averaging out the pulses into an overvoltage
condition as the spikes try to blow the filament.

A charger will make the stereo speakers hum loudly, VERY loudly if a cell
has died into high resistance. The charger's rectified pulses flowing
through the dead cell's high resistance (higher than milliohms of a
normal cell) create spikes on top of whatever DC voltage the battery
actually is.

If you're measuring the battery with a meter, the meter movement
(mechanical) or a digital meter averaging out the spike during its
measurment sampling cycle, don't give you any indication the voltage
peaks are actually THAT high. In a cheap boat radio you can hear the
spikes, your first indication of either a dead cell or corroded terminals
in the charging circuit at the battery, which makes the same whining in
the speakers.

(42 lurkers have just found out why the stereo is whining every time they
crank the beast...(c