SW Absorbtion Timers Awry [RE-wrenches]

[Phil Undercuffler]

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Does the problem persist if you unplug the battery temp sensors?  

Since the charge set points are based on the temperature compensated values,
glitches in the data sent from the temp sensors might be playing havoc with
the charge times.

It's a long shot, but what the heck.

Please note new phone extensions
 
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Phil Undercuffler
Technical Service Manger, ext. 0741
Conergy, Inc.
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-----Original Message-----
From: Robert Nuese [mailto:r.nuese at comcast.net] 
Sent: Thursday, May 04, 2006 2:40 PM
To: RE-wrenches at topica.com
Subject: Re: Digest for RE-wrenches at topica.com, issue 2075 [RE-wrenches]

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Dear Wrenches

Thanks so much for jumping into the fray!

Clive and David both suggest lines of inquiry that would be very  
helpful,
except that this system is not set up with generator auto-start and  
stop -
an important detail I left out, in what I feared was an overlong  
explanation.
Their very much appreciated suggestions:

> I've only seen this happen when both inverters are set at the same
> absorption time. I set the master inverter absorption time to a  
> longer time,
> and that cured the problem.
> Clive Wilkinson

And

> You've probably tried this already, but here goes. Back in the day
> (when we used Trace SW's) we programmed one inverter (of a pair)
> at lower bulk charging set points than the other, and also set the
> inverter with the higher bulk voltage for a longer absorption time.  
> This
> aided in the automatic shut down, as I remember. When you have
> already reached the bulk charged set point the batteries have been
> charged pretty good. So charging with only one inverter at that point
> is no big deal.
> What are the voltage set points for bulk?
> And what voltages are you seeing when the inverter's charge drops out?
> David Palumbo

In this case, its all being done manually, but the issue is that, on  
occasion
one, or both, inverters will go into float very early in the cycle,  
maybe
after only ten minutes - so it's a big pain. The users can never just  
turn on
the generator and then leave things unattended, but must periodically
check, otherwise they can be charging with just one inverter, not just
for the last 10, 20, 30 minutes, but for the last 1:50 minutes, or they
can come back and find they've been charging with zero inverters, and
not know for how long.

With a manually controlled generator, it shouldn't be necessary to have
staggered absorption periods or bulk settings, as it is with automatic
starting. In fact, it should normally run a bit smoother to have them be
uniform.

In answer to the questions,
The inverter bulk set points are both at 58v
The C-40 controller set points are both at 60v
The timer progression seems to happen only when the battery voltages
are at or above about 58v. This last I've not studied carefully, but  
will
monitor more the next time(s) I'm at the site - unfortunately in the  
hills
an hour from my home.



Dan has a number of suggestions and questions, I'll take them as he he
sent them:

> Do the inverters exhibit this behavior after a powerdown-reset,  
> prior to
> any programming (running factory default settings)?

I'm not certain, we'll try it out.

> Do they exhibit this problem with both AC input
> and AC output disconnected? Given that the new inverters exhibit the
> same problem, it seems like either a programming issue or perhaps an
> unusual wiring or load issue on the AC end. This is a long shot,  
> but since
> this is such a mystery, why not speculate?

Speculation is what I'm asking for. They do exhibit it with the AC input
disconnected, but I don't know about the output (or both together),  
we'll try it.

> Have you changed the Bulk Charge Trigger
> Timer from its default settings? If you've changed. menu heading 15  
> from
> the default setting of 00:00, this could affect when the absorbtion  
> timer
> begins counting, depending on AC input availability and on battery  
> voltage.
> If the bulk charge trigger timer (or some other programmed charge  
> cycle
> trigger) has activated a bulk charge cycle with no AC source  
> present, it
> seems that the absorbtion timer might begin to count if the battery  
> voltage
> is up to the absorbtion voltage set point (from PV charging), sort  
> of like you
> describe.

No, we've left the Bulk Charge Trigger at its default of 00:00, and I  
don't
know of any way we could have changed any "other programmed charge
cycle trigger".

> I would expect that Xantrex engineers (have you spoken to Ken
> Ripley?) should be able to tell you under which circumstances the
> absorbtion timer should count up (down?).

Yes, Ken has been the one most involved in the case, and has been very
concerned, and very helpful. His understanding, I gather, is that the  
timers
should only reset after completion of a bulk charge cycle, and that they
should only count (up) when in-spec AC is connected and the inverters
are in bulk charge mode. The timing goes in 10 minute increments. It's
suspended if the AC goes out of spec, but should be automatically  
resumed
when the AC stabilizes.

> Have a look at the note about "USING SLT MODE
> (SILENT MODE)" on page 82 of the old SW manual (Rev. B: Sept 1,
> 1999), and also have a look at the diagram on page 85 (though it  
> refers
> to SELL mode, it may hold a clue, especially with respect to  
> operation of
> the absorbtion timer based on battery voltage).

I've accumulated several SW manuals, but I only seem to have a later
edition. From what I see in the same sections in Rev. C: Feb 2001,
this all seems to depend on a non-default Bulk Charge Trigger setting,
which we don't have. Is there something different in the earlier  
edition?

> If you're able to watch the absorbtion timer counting, have you tried
> disconnecting the AC load while this is occurring? Perhaps the  
> inverter is
> powering a reactive load that somehow fools the inverter into  
> acting like
> there's an AC input (like the old SW islanding issue) -which, with  
> battery
> voltage above absorbtion voltage, might cause the absorbtion timer to
> count down.
> Dan Rice
No, we haven't tried that yet, we'll give it a try.

Since I'm a long way from the system, I can't immediately make the tests
suggested. Also, they can only be done when there is adequate solar
output, since the anomaly only seems to happen when there's adequate
solar charging, which is not entirely certain these days, as it's  
been cloudy
recently. I'll report back as soon as I can get some results.

In the meantime
Thank you all very much,
and. any more ideas based on the answers so far?
I'm curious if anyone else has more detailed info about the exact
functioning of the absorption timer. Does it indeed work as I've
understood from the Xantrex folks, or do any Wrenches know of any
further details or exceptions?
Thanks again
Robert Nuese




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