C40's and SW's [RE-wrenches]

Tue Feb 4 18:30:18 PST 2003

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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