<html><body><span style="font-family:Verdana; color:#000000; font-size:10pt;"><div>I'm with Dick. I liken grid tied inverters to diversion controllers. MPPT charge controllers (In Grid Tie Mode / talking to a HUB), pretty much just track a max power from the array. Good luck.<br></div><div><br></div><div>db<br></div><div><br></div><div><br>Dan Brown<br>Foxfire Energy Corp.<br>Renewable Energy Systems<br>(802)-483-2564<br><a href="http://www.Foxfire-Energy.com">www.Foxfire-Energy.com</a><br>NABCEP #092907-44</div><div><br><br></div>
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-------- Original Message --------<br>
Subject: Re: [RE-wrenches] Grid tie with BB<br>
From: <a href="mailto:Richard.L.Ratico@VALLEY.NET">Richard.L.Ratico@VALLEY.NET</a> (Richard L Ratico)<br>
Date: Sun, September 02, 2012 9:16 am<br>
To: <a href="mailto:re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</a><br>
<br>
Rich,<br>
<br>
If I understand your question, I think you're missing the functioning of the<br>
inverter. Working independently of the charge controller, it will sell to<br>
prevent overcharging the batteries. Correctly configuring the inverter's voltage<br>
thresholds accomplishes this.<br>
<br>
Dick Ratico<br>
<br>
<br>
--- You wrote:<br>
Wrenches,<br>
<br>
I'm have a mental block with battery backup systems such as the Outback<br>
Radian. Perhaps someone can help me get over it!<br>
<br>
Essentially these systems sell back power off the top of the battery bank<br>
and the array is maintaining the state of charge of the battery bank through<br>
traditional charge controllers. If you have a modest battery bank sized for<br>
limited use on critical circuits and a good size array for the benefit of<br>
net metering I would think it would be necessary to limit the current the<br>
charge controllers are capable of delivering to the battery bank to prevent<br>
damage to the batteries when the controllers are Bulking or Absorbing, but<br>
then it would seem that we limiting the utility of the larger array. If the<br>
current from the controllers was not limited they will self-limit as voltage<br>
rises, plus I suppose they will mostly be in float mode except when the<br>
batteries are cycled but again it seems that we are limiting the capability<br>
of the array compared to a straight grid tied system with a traditional grid<br>
tied only inverter.<br>
<br>
An example would be a 8000 watt array using a couple of flexmax80<br>
controllers with a string of 8 - L16 AGMs feeding a Radian.<br>
<br>
What am I missing here?<br>
<br>
Thanks <br>
<br>
Rich<br>
--- end of quote ---<br>
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