SW Absorption Timers Awry [RE-wrenches]

[Robert Nuese]

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Hi Travis

I think you may be confusing our problem with the issue described on
page 97 of the Xantrex manual (first paragraph of the "Automatic
Generator Control With Multiple Inverters" section).
That issue is that if both inverters have the same absorption time
setting, then it is possible that the "non-generator controlling"  
inverter
will go into float a bit early (because of minor variations in  
calibration),
and leave the other one to finish the cycle alone.
Usually it's just a  matter of 10 minutes or less. The solution is to  
set
the "non-controlling" inverter to run 10 minutes more. I've dealt with
this issue on half a dozen different installations, and as you say, it
is well known, and routinely dealt with.

Our problem is a bit different. On the system in question, sometimes
one inverter will go to float first, sometimes the other. It can be far
more than 10 minutes early, sometimes it's less than 10 minutes
after we've gone into bulk, even though the absorption time is set to
2 hours. Sometimes BOTH inverters go into float after less than 10
minutes in bulk. Then it doesn't matter if one inverter alone can hold
the batteries at bulk voltage level.

The current Xantrex technical folks say they were not familiar with this
problem before I reported it. Now they confirm that it does exist,  
and in
fact they've been able to reproduce it on all the SW inverters they've
tried.

Is this the same problem you are discussing, or something different?
Thanks for pitching in,
Robert Nuese




On Sep 26, 2006, at 6:53 PM, Travis Creswell wrote:

> Hello Robert,
>
> I must have missed your post from May 3rd.  Your problem is a well  
> known
> "factory feature" of the SW series when doing dual inverter set  
> ups.  I've
> got a bunch of them out there and they all do that.
>
> But I'm not seeing why you are concerned with a work around?   
> Sorry, I don't
> have time to look at all the old post right now.  To me this is only a
> problem if the inverter that remains in bulk can't hold the  
> batteries at
> bulk by itself.
>
> With industrial flooded batteries it's very important to regularly  
> use a
> hrydometer.  The Tri-Metric is a great meter and we use them in  
> every system
> but they really need to be programmed correctly.  There are some  
> fine tuning
> points that are carefully detailed in the comprehensive documentation
> included with the Tri-metric.
>
> And get rid of the C-40's if at all possible and switch to MX-60's.  
> You'll
> gain much better control of the charging with the array of "various
> modules".
>
> If these are flooded industrial batteries you need to take them 60+  
> volts
> every time the generator runs. Personally, I'd have no problem  
> taking them
> to almost 62 volts regularly.  As long as the cell temps stay under  
> 115f you
> should hit them with everything you can.  IMHO, proper charging of  
> off grid
> battery banks has much more to do with lots of amps (c/5 or better)  
> at high
> enough volts then amp hours.
>
> Best,
> Travis Creswell
> Ozark Energy Services


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