Battery Fuel Gauge [RE-wrenches]

Joel Davidson joeldavidson at earthlink.net
Tue Nov 7 18:37:34 PST 2006


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Hello Art,

Low grid voltage is not just a rural problem. There are "long skinny" 4kVA 
utility feeders in Los Angeles and other urban areas that occasionally drop 
to 95 VAC.

What is your SW5548 menu setting for #11 AC Inputs > Set input low limit 
VAC?

I don't think that the SW5548's limited surge capability is an issue because 
your system is grid-tied in the sell mode, but it's good to keep in mind 
that when SW5548s are off-grid or during a grid outage, they have almost no 
surge capability. They will shut down when an otherwise properly sized well 
pump or other motor load surges on. This SW5548 design characteristic was 
discussed a few years ago.

Joel Davidson

----- Original Message ----- 
From: "Art Weaver" <art at renovusenergy.com>
To: <RE-wrenches at topica.com>
Sent: Tuesday, November 07, 2006 12:26 PM
Subject: Re: Battery Fuel Gauge [RE-wrenches]


>
> Indeed, we may be seeing a similar (same?) problem with a grid-tied, 
> series-stacked SW5548 system installed in a rural area with a weak utility 
> grid.  Our working hypothesis is that low grid voltage (<215VAC) triggers 
> inverter shutdowns with *NO* error reported in the Errors menu. 
> Typically, one or the other of the pair of inverters shuts down, not both. 
> We've *never* seen an error code on either inverter.  Batteries are in 
> good shape - only a year old, showing good (dis)charging characteristics.
>
> In an attempt at diagnosis, we're now datalogging AC+DC voltage and AC+DC 
> current in and out of the inverters.  Any insights among those more 
> experienced with grid-tied Xantrex equipment would be much appreciated.
>
> ~art weaver
> Renovus Energy Inc.
> Ithaca NY
>
> Joel Davidson wrote:
>>
>> Wrenches,
>>
>> I had another SW4048 inverter shutdown last night and had to switch the 
>> inverter bypass breakers. Grid power was 108 VAC. I think (in addition to 
>> worn out batteries) the inverter menu 11 AC Inputs > Set input low limit 
>> VAC 108 default may be too low. Has anyone else with grid-tie systems 
>> experienced regular "light brown-outs"? What corrective action did you 
>> take?
>>
>> Joel Davidson
>>
>> ----- Original Message ----- From: "Joel Davidson" 
>> <joeldavidson at earthlink.net>
>> To: <RE-wrenches at topica.com>
>> Sent: Wednesday, November 01, 2006 5:00 PM
>> Subject: Battery Fuel Gauge
>>
>>
>>> Wrenches,
>>>
>>> So where's this going? Last Sunday afternoon, I experienced a Southern 
>>> California Edison (SCE) power outage followed by 3 evenings and counting 
>>> of grid power brownouts (101 VAC). My SW4048 line-tie inverter saw the 
>>> low grid voltage and went to stand-alone mode, but my four old Johnson 
>>> Controls GC12V100B batteries did not last long and the inverter did its 
>>> low-voltage shutdown. So I flipped the inverter bypass switch and put up 
>>> with low grid voltage (thank you SCE for shortening the life of my home 
>>> equipment). Trouble-shooting and flipping switches by flashlight and 
>>> re-programming the inverter the day may be interesting for techno-guys, 
>>> but the average on- or off-grid PV system owner (our customers) would be 
>>> frustrated and angry if their battery bank ran out of juice leaving them 
>>> in the dark.
>>>
>>> Finally, the question: What "battery fuel gauge" do you think is the 
>>> most non-technical customer-friendly (easy to use, intuitive, reliable, 
>>> etc.)?
>>>
>>> Joel Davidson
>
>
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