Imho, I would not be happy if I was reading 17v at the terminals of a fully
charged battery. But you could put an ampmeter on it and see.

"K. Smith" wrote in message
...
Derek wrote:
Briefly, I have an old (1967) 45 HP Chrysler engine. It has the old
"points & condensor" type ignition and it runs just fine.

I installed a Volt meter in the dash, and I run the boat off a deep
cycle battery, only because I carry a trolling motor in the event of
engine failure, not for fishing.

Problem : After running for a while, the Voltage across the battery
rises to about 17 Volts, damaging the battery and possibly damaging
any other equipment I might run off the system (lights, fish finder,
GPS etc.) I intend to install a toggle switch to isolate the (Purple)
Positive charging wire, and flip it on as required.

Is there a possibility that this will cook the diodes? The charging
system has no regulator, just a bridge rectifier. Is there a safer
place to "break" the circuit? The ignition system takes it's power
from the battery, no magneto.

I'd rather this "wasted" energy of boiling the battery be removed 'cos
this old motor needs all the help she can get.

Note : The 17 Volts is across the battery, not the open charging
system. Also, do deep cycle batteries have a lower internal resistance
that's causing this high voltage? All connections and battery are in
excellent condition.

Thanks,
Derek.


It takes voltage AND amps combined to cook the battery. Yes 17 volts is a
little high but on those old unregulated systems they could get away with
it because they didn't put out much power (as in volts plus amps)

This has only become a huge worry for people with the advent of elcheapo
digital multimeters, till now outta sight outta mind:-)

As for damaging electronics it's always "possible" but most unlikely,
modern stuff is well able to handle over voltage of that amount, a normal
alternator system will oft charge at 15-16 volts.

In the event you remain concerned, leave some load on it, the running
lights?? or similar, even a small load will reduce the voltage, because
again the sytem is low power output anyway.

K

The Krause lie of the day is:

Have you ever sailed from San Francisco to Hawaii? I have.
Have you ever rounded Cape Horn? I have, twice.
Have you ever transited the Panama Canal? I have.
Have you owned more than 20 boats in your lifetime? I have.
Have you ever sailed large boats competitively? I have.
Have you ever been hundreds of miles from land in a powerboat
under your
command? I have.