On Tue, 24 Jul 2007 10:14:12 -0400, Jeff wrote:
* wrote, On 7/24/2007 6:09 AM:
...
You can use it to check everything - charging? It will climb up to
about 14.4 volts and then drop off to about 13.6, or if you are using
a manual charger you can monitor voltages and switch the charger at
the appropriate time. How much power are your nav lights using just
switch them on and check the voltage. Ho! Ho! Turned the lights on and
the voltage driopped 0.1 volts at 12.7 volts. A little math and you
know how much power yout lights draw.
What math is that? How does the voltage drop at the battery tell you
the Amperage its delivery?
BTW, I agree about the DVM, its essential on any boat that has more
than a minimal electrical system. Better yet is an Amp-hour meter,
certainly pricey but worth every penny if you have larger loads, such
as a fridge, and tend to live off-grid.
I had, foolishly, assumed that he knew the resistance of the devise,
mainly I guess because the O.P. was talking about a low amperage mast
head light.
The problem with the amp hour meters is (I suspect) they aren't very
accurate. I admit that I've only read the manual on a couple of
different makes but they both talked about initializing the meters and
then later into the manual they mention that you need to re-initialize
(or maybe they said "zero") the meters from time to time..
I quite like the basic idea but given that as the battery ages the
charging time changes I cannot see how the meter can be absolutely
accurate and if it is only approximately then I can envision problems
although it certainly seems to make things simpler.
Bruce in Bangkok
(brucepaigeATgmailDOTcom)