Hi all,
I came across this thread when chasing battery monitors.Whilst the
thread originates from the boating fraternity, it raises several
issues which maybe relevant to 4wd.
Battery Monitor Thread
Quote:William_H
I feel obliged to make a comment. One thing you don't want on any
boat is more electronics. It usually means more worries and
dissapointment.
Yes with the aid of modern microcontrollers it is possible to very
accurately measure current over time into and out of a battery. but
what does that really tell you? The actual amp hour capacity of a
battery is a very variable quantity. In aviation in estimating the
time a plane could fly on battery alone, we ( government
legislator) used a factor of 55% of manufactyurer rated AH capacity
of battery. ie thats all you can reasonably rely on from a lead
acid battery during it's life. ie until it won't crank the engine.
( even that is a very subjuective guess. It is likely when
considering large capacity house batteries that the capacity could
fall far lower before you really noticed a problem. (especially for
those religiously never discharging below 50%) modern batteries may
be better but then in parctice many batteries may be found worse.
So while amp hours in and amp hours out might be interesting it
doesn't mean that you ca n get all the current out that you put in
or that the battery has anything like the capacity you may have
programmed into the device. ( or expect) So there is a contrary
opinion just so you don't go off thinking you have to have one.
regards olewill
Unquote:
Quote:jerryat
Hi Will!
I entirely agree with you!! We do not rely on the 'zero amps' of
the Battman to tell us the batteries are 'fully charged', as we are
fully aware that a good 10% or so extra is needed to achieve that!!
But what pretty
well all these gadgets do, is give you is a better
'idea' of the state of play and that's extremely useful IMHO. We
never discharge our batteries below 10-15% of apparent capacity and
as a consequence, they last us for many years.
No, the MAIN reason we installed one, was to measure as accurately
as possible (short of fitting a temporary ammeter in line to each)
the real current consumption of every piece of electrical equipment
on board.
Frankly the results were staggering. The manufacturers claims were,
almost without exception, for much lower consumption (in some cases
hugely so) so that any reliance placed on our total usage based on
their figures, would have been useless. OK, that doesn't matter
perhaps if you're basically weekending your boat, but when long
term cruising it's crucial!
The fact that the unit also gives us an accurate 'at a glance'
battery voltage was another factor in our decision to install one,
and our Battman has now been aboard for 13 years and done 40+
thousand
miles, so we are happy with it's long term reliability
too!!
So don't worry,we haven't 'gone off' thinking we have more than
we've got!!
Cheers Jerry
Unquote:
This goes a long way to explaining why there are contradictory
experiences in battery threads, in particular
[William_H]So while amp hours in and amp hours out might be
interesting it doesn't mean that you can get all the current out
that you put in or that the battery has anything like the capacity
you may have programmed into the device.
So......are these comments FACTUAL?
eng