The Classic is pretty good at catching spikes but it's a compromise in
design as to how high above the present
battery voltage a controller can quickly respond to a real rising
battery voltage and how often it will catch an
extremely fast noise spike and become a nuisance.
Another good test is, while a charge controller is running hard, turn
off the battery breaker to the charge
controller itself and watch the CC terminal voltage to see how high it
rises during that instance. Before the
CC turns itself off that is... That would be a worse case scenario
because the battery will not be holding the
voltage down at all. This method was used in the design of the Classic
but I haven't tried that in a while
but should be pretty good.
Regarding the "whip" effect (or the French version of the word), the
battery impedance should help
to slow down the battery voltage rise time after the grid or inverter
goes away but that time will vary.
The Classic won't log a high voltage unless it stays for more than like,
2 seconds or so but should catch
a high voltage within a second. Even if it does well, a battery that
rises fast to an overvoltage will
probably stay high because of the whip effect. Capacitors do this very
will too of course.
You could, I suppose, excess battery charge voltage back into the PV
array but we try NOT to do
this for various reasons. Either way, a short but not too high of
voltage spike (even 65V for 48V system)
should not hurt anything.
boB
On 7/21/2017 6:48 AM, Drake wrote:
Hello boB and Steve,
I haven't been able to make it to the site yet, but so far, no more
reports of spikes. I plan to try boB's suggestion of shutting off the
grid input while it is selling, to see what happens.
The spike did only last one second, so I don't think it is a chemical
whip effect. If the spike only lasted a fraction of a second, wouldn't
the Mate 3 still show the event lasting a second, since that is its
lowest level of granularity?
The array size is 2240 W and the Concorde battery bank is 305 AH at 48
V for a C/6.5 charge rate. The battery bank should have been fully
charged. If the grid went down and the Radian quit selling during a
heavy selling period, could that not cause a 1 second voltage spike,
or should the Classic catch it instantaneously?
Thanks,
Drake
At 11:49 PM 7/18/2017, [email protected] wrote:
The Classic can overshoot but not very much, normally.
I would try this...
Sell to grid while watching the battery voltage and then turn the
inverter breaker off
and see what the battery voltage does. If the battery voltage rises
to the mid 60V range
from a low sell voltage of around 52 or 53V, then something is really
amiss.
If the system has been in service for some time, you might also check
the capacity of
the batteries. They should not easily allow 65-ish volts. I don't
think that the
FM's communication can respond to keep spikes from happening any better
than it could without communications. Data packets just don't come
all that
often.
boB
On 7/18/2017 5:25 PM, Jerry Shafer wrote:
Wrenches
The Outback system with grid connection would be programmed for grid
connection all the way from the inverter to the Outback FM CC, using
a midnite CC this option may not be possible resulting to a CC push
if the grid disconnects resulting in a spike. the disconnect might
be from settings to tight or as it was said utility spikes. You
might thing that the battery bank should take it up but internal
resistance in the battery or to it may prevent it. The other thing I
would look at is connections, if there is any resistance in a
connection this could happen.
On Mon, Jul 17, 2017 at 2:36 AM, Drake
<[email protected]
<mailto:[email protected]>> wrote:
Hello Wrenches,
My client reported seeing an overvoltage error message on her
Mate 3 on a Radian system. The Radian is selling to the grid and
is being fed by a Midnite Classic 200. It has shown two spikes
so far, the last one going to 67 volts and lasting 1 second. The
batteries are Concorde AGM, 305 AH.
Does this momentary spike seem like a problem or a warning of
problems to come?
Thanks,
Drake
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