Terry K brought forth on stone tablets:
On Jun 26, 5:21 pm, wrote:

Can anyone think of any problem with adding another diode bank to my
90hp Merc 2cycle so that it could charge another different battery?
I assume that the diodes are nothing more than a bridge rectifier
setup so adding another set of diodes would just provide another
parallel load to the alternator stator coil. I assume that since the
alternator is by and large a current source anyway that the only
effect of adding another bridge rectifier is that some of the charging
current that normally goes to the starting motor would now get
directed to this other battery.

I know that there's other ways of doing this, battery isolators etc,
but it would seem that if I have space under there and have the
diodes that this would be a reasonable way to go about it.

Any reason why not? I'm no longer under warranty. Worst case if
there were excessive loading I could burn the stator coil of the
alternator if the current were not limited.

tks
Don


I would think that adding another diode block to the coils to charge
another battery would be the best answer, if you can get them wired to
the coils correctly.

It is the best way to maximise and equalise the charge to both
batteries. It is also the best way to overwork the charging coils in
your engine.

Terry K


I would think that this would be fruitless. If the alternator is
running flat out into one battery bank, it is not the diodes which are
the pinch point for electrical flow, it is the gauge of the wire in the
stator coils and/or the rotor (if it is not a PM alternator). Adding
another diode trio won't make any difference.

The alternator stator is a current source - but not a textbook one. It
has internal resistance - derived from the gauge and length of wire in
the coils.

bob
s/v Eolian
Seattle