Trace Sell back modes [RE-wrenches]

[Jeffrey Wolfe, Global Resources]

Todd Cory Said:

" have been asking Trace since I got this unit for a "silent sell" mode, 
where the unit would go into
it's silent standby mode when there was nothing to backfeed. The batteries 
sure don't need float
charging every night, and the overhead of running the inverter all night 
when not needed is way, way
more than the tiny amount of power the batteries get in the float charging. 
This seriously adds to
the already inefficient overhead of the unit, especially during the winter 
months when there is
sometimes very little daily gain."


That sounds like almost the right mode of operation. The only change I 
would make, for those systems that do power a house load, is to allow the 
Trace to continue to pass current through to the house through the transfer 
switch, but turn off the battery charger. The trick is that when the 
battery charger get's turned back on, it has to realize that there was no 
power loss, and that the batteries do not need a bulk charge.

I hear the problem, from Trace's side, is that their EPROM chip has no more 
room on it for code. Upgrading is a major redesign, not just a chiup swap. 
(I do not know why.) So I do not believe we will see a simple upgrade path, 
nor do I think we will every see an SW with these program features. I think 
these will be next generation.

Up in Vermont and NH Hampshire several people have been looking at this 
efficiency issue, and trying to get ways around it. About all we've been 
able to come up with is to have the inverter only selling back, no loads 
connected to it, and use the grid timer feature. Then also put a VERY short 
(10 minute) bulk charge time in. This will result in basically a pure 
sell-back system, but you will either lose a little solar output or use a 
little grid juice at the beginning and end of each day, depending upon how 
tight you set the grid timer.

This has been the biggest reason that I have not increased my own battery 
bank above 350 Ahrs and why I am trying to push customers into batteryless 
net-metering. Even with the new MPPT charge controllers, we still are 
estimating about a 15 - 20% gain in efficiency for a batteryless systems, 
even compared to a system with a small battery bank.

Jeff

Jeffery D. Wolfe, P.E.
Global Resource Options, LLP
A Woman-Owned Vermont Limited Liability Partnership
4 Kibling Hill Road
P.O. Box 51
Strafford, VT 05072
802/765-4632
802/765-9983 (Fax)
global at sover.net
www.globalresourceoptions.com

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