C40's and SW's [RE-wrenches]
Graham Owen
graham at solarexpert.com
Wed Feb 5 14:02:30 PST 2003
Hi Bill,
Thanks for the sound advice. When I wrote my long-term business plan,
with a lot of lessons learned from the 1986 collapse of the solar
industry, I vowed to only install products with at least two years of
untroubled local performance. This may sound crazy to some, but I have
only just recently started working with SB inverters. I don't like
making my customers guinea pigs.
Thanks again, from a slow lemming,
Graham
-----Original Message-----
From: Bill Brooks [mailto:billb at endecon.com]
Sent: Wednesday, February 05, 2003 1:42 PM
To: RE-wrenches at topica.com
Subject: RE: C40's and SW's [RE-wrenches]
Jay,
With all due respect to the Outback folks, for grid-tied systems I would
not be so quick to toss my C-40s for a Max Power controller, whether
MX-60 or SB50. The additional cost may or may not pay for itself over
time and the reliability is an unknown. I don't think anyone has enough
hard data to make that blanket assessment.
Our industry has been so quick to run like lemmings to the sea every
time a new idea or product comes on the market. I always like to ask the
lemmings why they are running so fast, where they are going, and for
what reason. They seldom can provide me with good information to join
them.
Bill.
-----Original Message-----
From: Jay Peltz, Peltz Power [mailto:jay at asis.com]
Sent: Tuesday, February 04, 2003 6:30 PM
To: RE-wrenches at topica.com
Subject: Re: C40's and SW's [RE-wrenches]
I think that any discussion of C-40's on large arrays, especially
intertie is a moot point.
Most interties are pretty large and so the use of a MPPT controller is
very cost effective and is any easy swap out. ( especially as the MX-60
fits the same KO's)
In regards to the higher voltages equalling higher power, yes but I have
never seen any change in the output of the SW with the higher input
voltages.
Peace,
jay
Peltz power
----- Original Message -----
From: "Jeffery Wolfe, Global Resource Options"
<jeff at globalresourceoptions.com>
To: <RE-wrenches at topica.com>
Sent: Tuesday, February 04, 2003 11:29 AM
Subject: RE: C40's and SW's [RE-wrenches]
> Bill,
>
> Although you're right that the C40 should never control, the point of
> the higher voltage settings is to make more power. We all know that
> the PV's will put out more power at higher voltages, so setting the
> inverter
higher,
> for float, is better. We also need to balance this with battery high
limits,
> and the fact that you need a pretty significant "dead band" in the
> control setpoints between the C40 and the Trace, due to inaccuracies
> in the
voltage
> meters in both units. (Trace told me 1.5 V, I'm typically using about
> 1.0 V).
>
> The 53.6VDC default on the inverters is also on the very low side of
> where we're floating batteries, even on-grid, today. We're moving
> hotter, more like 54.8 to 55.2. Batteries that float all year long
> tend to have
sulfation
> problems, and it seems that the hotter setpoints help reduce this.
> (Along with the little black boxes.) Couple this with the fact that
> on-grid
higher
> float voltages are going to produce more power, the case is made for
setting
> the floats about as high as the manufacturer's will let you. We do use
bulk
> mode, as it's good (IMHO) to bulk the batteries occasionally. So we
> set
the
> bulk up at about 58 VDC. This then pushes the bulks on the C40's up to
> 59
to
> 59.5, in order to provide as much dead band as possible.
>
> We've got three years on our double C40 / SW system, as well as
> several others around the area. The low set points "work", but are not
> the best
for
> power production (remember, we all complain about power production on
> PV systems), and are not necessarily the best for battery life.
>
> I do agree that the C40 float and bulk can be set the same, but it's
> more like setting the float to the same as a more typical bulk, rather
> than the other way around.
>
> I also always use a Fluke to set up the C40 (and any other
> controller). I never trust the little dials or displays. They can be
> wrong (on any controller).
>
> Jeff
>
> -----Original Message-----
> From: Bill Brooks [mailto:billb at endecon.com]
> Sent: Tuesday, February 04, 2003 1:10 PM
> To: RE-wrenches at topica.com
> Subject: RE: C40's and SW's [RE-wrenches]
>
>
>
> Graham,
>
> I believe that bulk charging is meaningless in a grid-connected
application.
> Since the system is floated all the time, except during a power
> outage,
the
> focus is on the float settings. I would set the bulk timer on the
> inverter to 0:00 so it automatically goes to float. The default for
> the inverter is 53.6 Volts for float and I think that is fine for most
> lead-acid
batteries.
> The key is making sure the C-40 is set at least one volt higher. It is
also
> critical that all controllers and inverters have temperature
> compensation probes installed and sensing basically the same
> temperature.
>
> Finally, check the C-40 while operating to make sure it is not
controlling.
> By testing the voltage drop across the C-40 positive battery and PV
> array inputs, you can tell whether it is controlling. The voltage
> should always
be
> below 0.75 Volts, otherwise it is controlling. It should only control
> in
an
> outage. Set the C-40 bulk at the same as the float, since the array
> should not be bulk charging the battery anyway. Bulk charging doesn't
> help a battery that stays at float all the time. It can actually hurt
> a VRLA battery by overcharging it if you allow it to bulk for more
> than a
half-hour
> or so. Hope that helps. Others may see it differently but I have over
> four years of grid-connected experience with my C-40s and SW.
>
> Bill.
>
>
> -----Original Message-----
> From: Graham Owen [mailto:graham at solarexpert.com]
> Sent: Monday, February 03, 2003 9:01 PM
> To: RE-wrenches at topica.com
> Subject: C40's and SW's [RE-wrenches]
>
>
> Dear Colleagues,
>
> I need some Wrench assistance with a PV service call, for the Xantrex
> Power Module system (or power panel for that matter), you have to set
> the C40 charge controllers and the SW inverter so that the inverter
> can sell PV power to the grid without the controllers restricting
> current into the inverter in the first place. I am trying to determine
> which set of values works the best.
>
> Are these good figures?
>
> C40 bulk 56.0
> float 55.0
>
> inverter bulk 54.0
> float 53.2
>
> Thanks in advance!
>
> Graham
>
> P.S. Joel, I am working on finding your CPUC answers, I was working
> out of town today.
>
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