balancing output from multiple controllers [RE-wrenches]

[jberdner at sma-america.com]

Wrenches:

The multiple controller problem was addressed in the Power Centers we
built at Pulse (now Connect Energy).
They used one master control board to control multiple sub-arrays in a
closed loop fashion.
The off-the-shelf PC 500 could do up to 240 Amps with 4 sub-arrays at
12,24, or 48 Vdc and you had coordinated bulk / float / equalize.
The largest custom unit we ever did was 400 Amps at 240 Vdc with 6 sub
arrays.  That one was not quite off-the-shelf but it worked great.

I am not sure if they are still building them but it might be worth a
call.

If you have any questions, or if I can be of any further assistance,
please do not hesitate to contact me.

Best Regards,

John Berdner

SMA America, Inc.
20830 Red Dog Road
Grass Valley, CA  95945
530.273.4595 (voice)
530.274.7271 (fax) 


-----Original Message-----
From: Steve Willey, Backwoods Solar [mailto:steve at backwoodssolar.com] 
Sent: Monday, September 23, 2002 2:57 PM
To: RE-wrenches at topica.com
Subject: Re: balancing output from multiple controllers [RE-wrenches]

Jeff: Its impossible to get multiple controls to act at the exact same
voltage/time, even when meter set to same number, unless they are
interconnected so that only one is controlling the action of all of
them.
None of the common controls we use are set up to do that.  Therefore
when
any one starts backing off the charge even a second before the others
would
have done so, this moves battery voltage farther away from the
trip-point of
the next controller, delaying it's action. Especially when a C-40 jumps
down
to float from bulk/absorption stage. The other controls still in
absorption
hold battery voltage above float, causing the control/s in float to go
to
zero amps.

Steve Willey       steve at backwoodssolar.com
www.backwoodssolar.com
Backwoods Solar Electric Systems
----- Original Message -----
From: "Jeff Yago" <jryago at earthlink.net>
To: <RE-wrenches at topica.com>
Sent: Sunday, September 22, 2002 8:11 AM
Subject: RE: balancing output from multiple controllers [RE-wrenches]


.. I usually end up with two to four Trace C-40's or
> C-60's and at least one is always "stepping" on the others causing
them to
> think the battery is full and stop charging.  Yes, I always use a
quality
> meter to set the pots the same settings, and make sure the temperature
> sensors are located together at the same point on the battery bank.
>
> I know this only will happen when the battery is reaching a fully
charged
> level, but you would have thought all of the controllers would back
off
> together and each start lowering their output instead of one or two
staying
> at full output and the others going to zero.  I assume the output of
the
one
> or two at full is providing the same charging as would happen if all
were
> operating at half output, but there is always the client who thinks
part
of
> his array is dead.  What's the deal?
>
> Jeff Yago
>

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