Tri-Metric program question [RE-wrenches]
Mick Abraham
mick at abrahamsolar.com
Thu Oct 12 07:43:16 PDT 2006
Building on my relay suggestion posted a few daze ago (copied below): if
the relay was an "on-delay" type, the delay could be set for 12 hours or
however long a grid powered recharge is calculated to take. When grid
comes back up, the TM-2020 meter would continue to be powered up and
running until the time out period occurs. This would totally avoid the
problem of a reset to 100% occurring as a result of a short term return
of grid power. Now the question is: are the meter program settings
permanently non-volatile?
Mick A.
Mick Abraham wrote:
>
> Here's an off-the-wall idea for Allan's Tri-Metric issue: So long as the
>
> grid is up and running, the end user doesn't need any battery state of
> charge information at all, so: A SPST normally closed relay with a
> 120vAC coil could interrupt the DC positive going to the meter so long
> as the grid power is energizing the relay coil.
>
> If the grid goes dark, the deadman relay would power up the meter, and
> the TM-2020 always displays 100% when it's first powered up. TM-2020
> program settings are retained even with no power to the meter (but I
> don't know if that's permanent non-volatile memory).
>
> Here's an advantage: the end user can confirm grid blackout status by
> noting that the Tri-metric is lit up. Here's a (possibly huge)
> disadvantage: if the grid comes up briefly then goes back out, this
> would reset the TM back to 100% which may falsely mislead the end user.
> Therefore, this suggestion is worth considering if the blackout pattern
> tends to be off, staying off, then on for a long time. If the balckout
> pattern tends to be off for awhile, then briefly on, then off again,
> this suggestion injects a new batch of problems.
>
> Just thinking outside the box,
>
> Mick Abraham
>
> Allan Sindelar wrote:
> >
> > Wrenches,
> > We have been including a Tri-Metric monitor with our Outback
> > grid-tie-with-battery-backup systems, so that the homeowner has some
> > sort of
> > state-of-charge indication during an outage. We have learned to be
> > selective
> > about whether to include a Mate as well, as it's not as user-friendly
> > for
> > our typical non-technical grid-tie customer.
> >
> > The issue is that the Tri-Met is fundamentally designed for off-grid
> > use,
> > and uses charged-voltage and charged-current parameters to reset the
> > monitor
> > on a regular basis. As the PS1 keeps the batteries in float, the Tri-Met
> >
> > can
> > develop an accumulated error that is only reset after a grid outage and
> > recharge cycle, which could be months at a time. We have seen this
> > happen,
> > where the % of full slowly drifts down over days or weeks.
> >
> > I called Ralph Heise about this, and he had suggestions, but no clear
> > answers - in fact he is looking for ideas that have worked too. He
> > suggested
> > the following two ideas, which make sense in theory:
> > 1. Set the charged voltage parameter below the float voltage (far enough
> > below to accommodate the effect of hot-weather temperature compensation
> > -
> > say 52.4V if float is at 53.6 - and set the charged current setpoint
> > just
> > above the float current - 1 or 2A, I would guess. This keeps the monitor
> > reading 100% while in float, and the combination of voltage and current
> > settings would prevent premature resetting based on voltage-above-float
> > alone.
> > 2. Set the charge efficiency factor unrealistically high - say at 100% -
> >
> > so
> > that this keeps the % reading at 100% while in float. This would make
> > the %
> > reading slightly high during outage cycling, but it could be easily
> > reset
> > each charge cycle.
> >
> > Has any Wrench out there come up with a good solution? How would you set
> >
> > up
> > a TriMet for this application? Or otherwise, how do you address the
> > bigger
> > issue of a monitor that is used only during an outage?
> >
> > Thanks in advance,
> > Allan at Positive Energy
> >
>
>
>
> Abraham Solar Equipment
> Pagosa Springs, CO
> www.abrahamsolar.com
Abraham Solar Equipment
Pagosa Springs, CO
www.abrahamsolar.com
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