>...
>What is the battery voltage when the engine is running?
>You can also disconnect the regulator from the battery, BUT KEEP THE
CAPACITOR CONNECTED TO THE REGULATOR! and run the engine (preferably with
all avionics switched off) and measure the voltage across the capacitor.
>Voltage for the standard Rotax regulator should be appr. 13.7 Volts.
>Let me know how this works out so we have a starting point.
>Frans
Jeff,
These are good points from Frans. Just an additional comment. IF this is a
shunt regulator (I think it is), it regulates by shorting out the alternator
phase(s) to ground, once the voltage starts to go higher than its internal
setpoint (lets say somewhere around....14-15 volts or so, at the regulator).
If there is no load to the alternator such as accessories and a battery, the
regulator has to soak up ALL of the excess power from the alternator. At
high engine speeds, this can become very significant. Without cooling, it
can be very hard on the regulator. I suggest that if you test (yes,
DEFINITELY with the capacitor) without the battery hooked up, try not to run
the engine too high in rpm for too long so as not to risk damaging the
regulator. IMHO, test with battery in circuit if possible, unless the
battery itself is suspected. A charge voltage between 13 and 14 Volts I
consider good, and 13.8 ideal. Anything over 12.7 is charging the battery
(for lead acid technology).
Your battery tested at 12.5. That means its about 84% charged, assuming it
is newer and in good shape (or the reading would be higher), does not have
any significant load connected to it, or charged within a half day or so of
the reading (voltage reading will be high after a charge, but slowly drop to
its normal value). If it had measured 12.7V, it would be fully charged.
11.94V would have signified about 10% charge. No-load checks are not the
best way to check a battery and these values only work for lead-acid, but it
gives an idea of its charge status. This paragraph is just a bit of an
aside, but might help if wondering about charge state of the battery or
battery diagnostic. If only one cell is bad in the battery (for example,
shorted plates), the battery would read low by about 2.1V. Assuming a fully
charged, it would be below 10.6V for the voltage reading. If it has a
cracked post, its value won't seem to make sense every time you measure it
...charging....loaded....just sitting there... and it will drive you (I mean
me) crazy. Good Luck!
Regards,
Greg
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