BoatBanter.com - View Single Post - And Aw a-a-a-a-a-y-y we go!

Jeff

* wrote, On 7/24/2007 11:10 AM:
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..

They are quite accurate in a sense, but I think mine gets confused by
the number and variety of charge sources and sinks. This leads it to
automatically adjust its concept of charge efficiency poorly.
Recently I realized it was using 73% when a better choice was 87%.
However, if you understand that is happening, its easy to compensate.
In my case, I knew that it was losing about 15 Amp-hours a day. A
few hours of charging, as when powering through Wood's Hole is enough
to reset the meter. On a day by day basis, when my alternator charge
rate drops down to around 40 Amps, I know the 450 Amp-hour bank is at
about 90%.

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.

Its better on the usage side than on the charging side. But still,
its infinitely better than nothing.