Mac,
Adding to Dan's sage advice:
No inverters have amp-hour meters built directly into them.
Magnum and Outback have the ability through their respective BOS
peripherals to provide that information to the user, but it's not
part of the inverter. Both are shunt-based, meaning that they base
SOC and other data on actually measuring current flow into and out
of the batteries, as does the TriMetric.
Schneider XW's peripherals also offer user-friendly SOC, but it's
not shunt-based and is thus a much rougher approximation; in one
system of ours a 2HP well pump was a large enough draw to provide a
premature low-battery warning.
Apollo's inverter has no SOC indication capacity. Voltage and
instantaneous current are the only parameters that can be accessed
on the inverter's display. Anything else requires a data feed to
their software on a computer. Apollo's charge controller has SOC
capacity built in, and relies on a shunt to provide measurement, but
the algorithm is faulty; that is, it doesn't count up and count down
at the same rate (this is independent of charge efficiency factor,
i.e. Peukert's coefficient) and relies on the switch into float to
correct the measurement error. This means, for example, that it will
not match the reading on a TriMetric with equivalent setup
programming.
Years ago we decided as policy that we wouldn't sell a system of any
size without a TriMetric (or, back then, an E-Meter). Our logic was
that a tiny system with a clear and user-friendly way to know what's
going on inside the invisible world of batteries and electrons was
better than a larger system with no way to know what was going on.
My record was a $1,200 system, meaning 1/6th of the entire system
cost went for the system monitor. I told customers that if they ever
regretted the $200 for the monitor I'd take it back. Nobody ever
took that offer up.
Allan
Allan Sindelar
[email protected]
NABCEP Certified Photovoltaic
Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Positive Energy, Inc.
3201 Calle Marie
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
On 10/10/2011 10:21 AM, Dan Fink wrote:
Mac;
I'll give it a shot here.
1) Yes. EVERYTHING that might consume or produce energy needs to
be connected thru the shunt off the main negative battery terminal
for the amp-hour meter (watt-hour meter, these days) to work
correctly;
1a) I am just getting familiar with the Outback Mate and
Flexnet DC stuff, as we mostly deal with much smaller systems and
just use a trimetric, BUT if you program the Mate correctly, it
appears you can tell it exactly what that functions of multiple
shunts in the system are.....as in, one shunt is wind power in,
one is PV in, one is inverter use, maybe one for DC loads, and the
meter then knows what to tally as gain and what as use. just not
enough experience here with this fancy-pants monitoring networking
stuff. I like the trimeteric.
2) Don't know.
3) Your first step after installing an amp-hour (w-h) meter is to
charge the battery bank full and into float, so the meter learns
an initial "zero" and starts working correctly (counting down from
full). And set the charge controller(s) and the meter so that
working together they will trigger this meter "zero" setpoint. So
if you install one on a system with an old battery bank it will
"learn" that setpoint for the old batteries right away.
3a) As far as how much these meters can actually "learn" I am
skeptical. But if you see big discrepancies -- large tallys of
positive amp-hours for example, or large negative readings when
the batteries show "full"....you can adjust the Peukert
coefficient on the meter to be more accurate for the aged battery
bank. As far as how this affects the "learning" ability, changes
all that, I just don't know.
So, as far as 3a) be aware of it, and maybe tweak the meter
settings if amp-hour readings are consistantly above or below
zero. Many off-grid folks only dream of positive amp-hour numbers.
LOL
Anyway, that's how I would approach it.
Dan Fink
Executive Director;
Buckville Energy Consulting
Buckville Publications LLC
NABCEP / IREC / ISPQ accredited Continuing Education Providers
http://www.buckville.com/
[email protected]
970.672.4342 (voicemail)
970.373.1311 (fax)
mac Lewis wrote:
Hello wrenches,
I am a "greenie" and am curious to know more about amp hr
meters. I've gone on quite a few service calls on existing
systems in the area, and I've never seen one on any of the
systems around here. With that being said, I know on some of
the new inverter/chargers incorporate these in their devices,
Apollo Inverters for example. My questions are:
1. Is the sole purpose to measure energy into and out of the
batteries?
2. On modern inverters such as the XW, is the SOC meter on the
control panel based on Amphrs or is it simply a voltmeter?
3. Does an Amphr meter need to be calibrated to older batteries
to account for the increase in internal losses? If so, how?
Thanks in advance. I really appreciate tapping into this
amazing knowledge base.
--
Mac Lewis
*
"Yo solo sé que no sé nada." -Sócrates
*
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