"padeen" wrote in
news
why would the charger react badly to a normal start? This is, one
must assume, a start from a healthy battery.
Padeen


Starting means nothing. The charger simply puts out all it can during
starting, no matter how it's connected. I'm talking about leaving 20A of
load running, the lights/fans/stuff. As long as the circuit is like new,
no problem. But, this is a BOAT. Noone is going to pull apart the
electrical system and clean all the connections every 6 months. Electrical
systems on boats I meet are hard to get to, damned near impossible to pull
apart and clean. Now that 20A load is operating through BOAT connections,
all corroded from the bilge humidity, the occasional splash of seawater in
the bilge on a rough day. Ahh...those are more reality. Now, the
conveniently-connected charger is seeing a .5V drop from the battery switch
to the battery, or wherever you have the charger connected. This subtracts
from the battery's actual voltage every time someone turns on a light. So,
the charger reacts by increasing its output more than the load needs to
compensate. If it were independently connected to the battery, none of
this would matter as the charging current isn't in the path with the load
current.

Someone else mentioned their AM/FM radio buzzing. The charger connected as
you wish, not to the battery directly, will also cause any resistance in
the path to the battery to modulate the DC with charger pulses, making
electronics connected to it buzz or humm (or in the case of an alternator,
whine). This is another case for connecting the charger directly to the
battery posts, where the only way it will cause the buzz is if the battery
has a dead cell.

I'm an electronic technician. Another reason I don't like the charger
connected upstream is safety for the expensive electronics on board. If
any connection becomes loose between where the charger is connected and the
battery, the charger's full pulse voltage WILL be applied to the DC power
supply lines...18-22 volt pulses! This will destroy electronics. Unless
the battery, itself, becomes open...a directly-connected charger cannot
overvoltage the electronics. In your hookup, only one screw has to come
loose or one connection opens with corrosion and blewee!