[RE-wrenches] Amp hr meters

Tue Oct 11 05:54:56 PDT 2011

Thanks for the input guys.

On Mon, Oct 10, 2011 at 2:15 PM, Allan Sindelar <
allan at positiveenergysolar.com> wrote:

> **
> 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*
> *Allan at positiveenergysolar.com* <Allan at positiveenergysolar.com>
> 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* <http://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/
> info at buckville.com
> 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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-- 

Mac Lewis

*

"Yo solo sé que no sé nada." -Sócrates
*
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