sw5548 in sell back mode [RE-wrenches]

Bill Brooks billbrooks7 at earthlink.net
Fri Nov 16 17:28:29 PST 2001


Kirk,

Here is the message. This is certainly not ideal but that's because the SW
wasn't designed to do this very well.


Here is the method I found to be most effective:

INVERTER SETUP (MENU 9)
set to SELL

BATTERY CHARGING (MENU 10)
set ABSORPTION TIME to 0:00 on both machines.
set MAX CHARGE AMPS to 1 amp on both machines.

BATTERY SELLING (MENU 17)
set MAX SELL AMPS to X amps on both machines. (where 2X is the Max AC amps
that the PV array can produce. (e.g. 4000 Watts should set both to 18
amps --18A*120V=2160Watts)

Both temp comp probes must be installed so as to operate at the same
temperature. I have tried adjusting the float setting and that also works
particularly for an inverter that is out of DC calibration. They still get
out of wack at times at different temperatures because the slope of the temp
comp probes are usually not the same. This should keep both machines selling
as evenly as they can and limit each machine to a maximum of half the AC
Watts output. The one amp MAX charge amps keeps one unit from charging while
the other one sells.

Try it and see how you like it.

Bill.


> -----Original Message-----
> From: Kirk Herander [mailto:kirk at vtsolar.com]
> Sent: Friday, November 16, 2001 2:55 PM
> To: RE-wrenches at topica.com
> Subject: Re: sw5548 in sell back mode [RE-wrenches]
>
>
> Thanks. I was initially concerned that inverter #1 had a problem
> that would
> never allow it to sell, but since figured out that they can be somewhat
> balanced if bulk charge(ie sell) voltages are staggered by several  vdc.
> Still seems odd, though.
>
> -----Original Message-----
> From: Bill Brooks <billbrooks7 at earthlink.net>
> To: RE-wrenches at topica.com <RE-wrenches at topica.com>
> Date: Friday, November 16, 2001 11:28 AM
> Subject: RE: sw5548 in sell back mode [RE-wrenches]
>
>
> >Kirk,
> >
> >Aren't dual SWs fun. Welcome to balancing hell. There was a
> thread on this
> a
> >few months ago. I'll try to dig something up for you.
> >
> >Bill.
> >
> >
> >> -----Original Message-----
> >> From: Kirk Herander [mailto:kirk at vtsolar.com]
> >> Sent: Thursday, November 15, 2001 5:27 AM
> >> To: RE-wrenches at topica.com
> >> Subject: sw5548 in sell back mode [RE-wrenches]
> >>
> >>
> >> Hi folks,
> >>
> >> I have a dual SW5548 power panel programmed for sell back.
> Both inverters
> >> are programmed identically -
> >> bulk & float set to 52.0 volts, absorption time 0 hours, max sell amps
> 30,
> >> max charge current 30.0 amp.
> >>
> >> The system includes a 5 kw array. I assummed that both inverters
> >> would sell
> >> power back equally, but I am witnessing an imbalance.
> >> During a partially sunny day, with the batteries at the sell voltage,
> >> Inverter #1 was showing a positive 1 - 3 amps on AC input, while
> >> inverter #2
> >> was showing -13 amps being sold back. In addition, when the PV is
> >> turned off
> >> and the batteries are floating at 52.0 volts, inverter #1 is
> >> reading +5 amps
> >> on AC input, inverter #2  reading -4 amps. I'd think that
> charge rate at
> >> float would be balanced also, but no. The inverters' outputs are not
> >> connected to any  AC loads during these observations. Any ideas?
> >>
>
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