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<div class="moz-cite-prefix">I've never seen an inverter not
disconnect on low voltage. My understanding is that they just
can't operate below a certain threshold.<br>
However, I have seen behavior as described caused by DC loads that
did not have a LVD in place. Were there any other DC connections
to the battery bank besides the inverter?<br>
Once the whole bank gets low enough, even the charge controllers
will not reconnect, and the entire bank is quickly ruined.<br>
This is why I rarely use DC direct loads anymore, and If I do, I
always recommend a LVD.<br>
Any chance of a short circuit in the cabling before the inverter?<br>
The only other thing I could think of is a shorted cell in one of
the batteries, that then drained the rest of the batteries.<br>
<br>
<br>
<pre class="moz-signature" cols="72">R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760</pre>
On 12/17/2014 10:36 AM, Corey Shalanski wrote:<br>
</div>
<blockquote
cite="mid:CA+SmqZ1krVjUkkTTYhBh1zryGqwHzfJ+PSNMXoZ3ebQDHvtgpw@mail.gmail.com"
type="cite">
<div dir="ltr">Clarification and Update:
<div>- I believe I may have inadvertently thrown Magnum under
the bus in in my initial post. <br>
<div hspace="streak-pt-mark" style="max-height:1px"><img
moz-do-not-send="true" style="width:0px; max-height:0px;"
src="https://mailfoogae.appspot.com/t?sender=aY3NoYWxhbnNraUBqb3VsZS1lbmVyZ3kuY29t&type=zerocontent&guid=dab0a56b-2f33-4542-ab89-2eb7e81192f3"><font
color="#ffffff" size="1">ᐧ</font></div>
<div class="gmail_extra">While on site yesterday I did speak
with Magnum's customer support about my findings and they
advised to try to trickle charge the batteries up to the
minimum threshold at which the Magnum inverters would turn
back on. From there we will hopefully be able to run some
more determinate tests. My question about the
low-battery-cutout was more intended to explore whether
others have ever experienced any similar issues with this
protection feature. I am finding out that the feature is
only relevant during inverting (not charging) mode and so
would imply that the utility feed had been cut, which does
not appear to be the case.</div>
<div class="gmail_extra">- Our battery distributor has lent us
a 12-circuit trickle charger - one set of alligator clips
per battery. I am planning to re-visit the jobsite later
today to put each battery on a trickle charge, which I am
told will take 1-2 weeks for any lasting change to take
effect. The distributor advised to reverse the leads on the
batteries with negative voltage, hoping that they may be
recoverable as "reversed pole" batteries thenceforth.</div>
<div class="gmail_extra"><br>
</div>
<div class="gmail_extra">--</div>
<div class="gmail_extra">Corey<br>
<div class="gmail_quote"><br>
</div>
<div class="gmail_quote"><br>
</div>
<div class="gmail_quote">On Tue, Dec 16, 2014 at 8:27 PM, <span
dir="ltr"><<a moz-do-not-send="true"
href="mailto:cshalanski@joule-energy.com">cshalanski@joule-energy.com</a>></span>
wrote:
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><br>
Wrenches,<br>
<br>
I visited a customer today whose grid-tied battery
backup system suffered<br>
some sort of catastrophic failure, and now I'm trying to
play detective to<br>
figure out what happened and whose equipment/design is
to blame.<br>
<br>
Here is what I know so far:<br>
- System is ac-coupled with a Sunny Boy 7000 (7.85kW
array), Magnum<br>
MS4448PAE (x2), 3 strings of 4 12v batts (705Ah total)<br>
- Site visit was triggered by the Sunny Boy registering
zero output via<br>
online monitoring.<br>
- SPST Solid state relay installed on Sunny Boy output,
controlled via<br>
Magnum router, serves as secondary overcharge protection
to Magnum's<br>
frequency shift feature. Technician who initially
responded claims he<br>
measured 240v across the relay's terminals - relay
manufacturer claims this<br>
is "100% impossible". We removed the relay from the
circuit, and the Sunny<br>
Boy is again operational.<br>
- On arrival I found the Magnum display showing a "Low
Battery Charge"<br>
message with the bank measuring ~4Vdc. The individual
batteries were in<br>
various states of charge, ranging from high of 6.3v to
low of -2.6v. These<br>
measurements were taken at rest, all battery cables
disconnected, and yes<br>
three of the batts were registering a negative voltage.<br>
- Customer reports that he was not aware of any recent
prolonged power<br>
outages.<br>
<br>
The three potential suspects would seem to be:<br>
- SS relay: The customer is convinced that this is the
weak link in the<br>
system and somehow triggered this failure. I am not so
convinced but would<br>
be interested to hear recommendations for properly
testing its<br>
functionality.<br>
- Magnum equipment: Since there is low-battery-cutout
protection, why would<br>
this feature not have activated and prevented the
batteries from draining<br>
so low?<br>
- Batteries: I am not very familiar with modes of
failure, but our<br>
distributor suggested that an internal short could be a
possibility - what<br>
might have triggered this?<br>
<br>
Clearly I am fishing for potential leads here, so any
suggestions are<br>
welcome.<br>
<br>
Thanks!<br>
--<br>
Corey Shalanski<br>
Joule Energy<br>
New Orleans, LA<br>
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