[RE-wrenches] Using a Midnite Classic for Hydro

[boB at midnitesolar.com]

Jeff,  I am sorry you did not get a proper answer from tech support to a 
very basic question like this.
I don't know who you talked with so we will flog all of them equally.

I am glad that particular sentence was removed from the manual as it was 
not correct.  You can only
keep the charge controller ON if it is safe for the batteries to do so.

The reason that the Classic goes to resting is because raising the input 
voltage is (usually) the only way to
reduce battery voltage and current on its own.  Insomnia will not keep 
the Classic operating above 250 volts
input...  What "Insomnia" does is to keep the Classic from going to 
Resting due to low power output (< ~20 watts).
It won't help when the batteries are full or over full.

Since you are VERY slightly over 250 volts when free-wheeling, the first 
thing I would try is to turn OFF
the Classic mode and adjust the nozzles or flow to the turbine until it 
drops below 250 volts.  Then no
matter what, it will turn on...  That is, as long as the water flow does 
not increase too much to cause
the voltage to rise above 250 volts again when nobody is looking.

Another thing that can be done, or in addition to reducing the free 
running Voc is to lightly load the
turbine with a resistor.  Better yet, use  2 or 3 resistors to load the 
AC side a wee bit.  This works well
especially if the Max Power Point voltage is quite a ways below the Voc 
so these resistors don't have
to dissipate all that much power.  I would think that this method would 
not be necessary though.

NEXT thing to do is to adjust the Classic's battery charge set point 
voltage to somewhat higher
than that of the FM charge controllers so that the Classic is almost 
always charging (when not in Float).
OR, adjust the FM60/80 charge voltages slightly lower than the Classics' 
set point voltage.
Or, a compromise, one slightly higher than wanted and the other slightly 
lower charge voltage
to give both systems that "distance" between them.  This way, the FMs 
will always be helping out
in MPPT modes and Absorb/Float just won't matter much where that current 
comes from.
This method will mean that the Classic is always loaded some except for 
those times when the
charge current required from it is zero or very close to zero.

Roy Rakobitsch also has a good idea which is closer to being a Clipper 
by using a 3-phase AC SSR,
(3 Triacs), connecting all 3 phases of the turbine together. Doing this 
on the AC side is important.
You don't want to short out the rectified DC input to a charge 
controller for various reasons.
If you go this route, the best control is to use Aux 2.  Be sure to go 
to Clipper mode to make
sure it is set to AC mode.  You could then use Clipper mode or PV ON 
HIGH mode using
higher frequency PWM activation of the SSR.  I like the Teledyne 3-phase 
triac SSRs personally
if you decide to go this route.

First, just turn down the flow slightly to reduce that free running 
Voc.  That is probably the
quickest, simplest and cheapest method.

boB




On 3/19/2015 10:26 AM, Windsine Inc. wrote:
> You could use a triac to feed AC from turbine directly to the dump 
> load just before HyperVOC using the Aux relay in classic to fire the 
> Triac. Then program the Aux logic to revert to normal when turbine 
> voltage/RPM drops from dump load loading.
>
> Kinda like an Aux triggered bypass circuit
>
> Roy Rakobitsch
> NABCEP Certified Small Wind Installer®
> NABCEP Certified Solar PV Installer®
> NYSERDA eligible Small Wind installer
> Certified Advanced Tower Climbing, Safety & Rescue
> Wind/PV Design Engineer
> Windsine LLC
> 631-514-4166 <tel:631-514-4166>
> www.windsine.org <http://www.windsine.org/>
>
>
> On Thu, Mar 19, 2015 at 11:53 AM, Jeff Oldham <starpower4u at juno.com 
> <mailto:starpower4u at juno.com>> wrote:
>
>     Finding this application quite frustrating - Harris 120Vdc 1kW
>     turbine, Classic 250, 48V batt., 1200W load dump. The manual
>     downloaded just before purchase stated: "This mode will NOT go to
>     resting even when the input has been disconnected and will always
>     stay awake so the turbine has the least chance of over-spinning."
>     It now seems that this is not the case and this sentence is no
>     longer in the manual. My installer cannot get Midnite to confirm
>     one way or the other and they have been guessing for over a month
>     on how to keep the CC from going into RESTING that open circuits
>     the hydro and puts the CC into hyperVOC at 253V and will never
>     reconnect. To complicate things there is also ~4kW of PV on
>     FM60's, when they drive up batt V. to above what the Classic wants
>     it drops into RESTING and back into HyperVoc. Midnite has been
>     very responsive and have suggested every possible setting and
>     combination and my installer has made the 3 hour RT drive far too
>     many times to only find the most recent "suggestion to try"
>     another approach not working. INSOMNIA does not do as the name
>     implies and still allows the CC to step out if external charging
>     elevates the V above what the Classic wants. i.e. FM60 in Bulk,
>     Absorb or EQ. when the Classic wants to Float.
>     I fully realize that the Clipper will deal with this for a
>     considerable amount of money, but I've heard of several folks
>     using a Classic or Outback w/o a Clipper to deal with turbines w/o
>     allowing freewheeling and runaway VOC. If the turbine is not
>     dropped by the Classic the VOC will never exceed 120Vdc. Is there
>     anyone of you out there that knows:
>     1) Is there a way to keep a Classic from ever moving into RESTING,
>     a true INSOMNIA? If it will not do as originally stated in the
>     manual I need someone to step up and say so, so we can stop
>     guessing and wasting time.
>     2) If so what is the secret, please?
>     I really like all of Midnite's products and they are better than
>     most with reasonable prices, support has always been 1st rate.
>     This application oddly seems to have all of us at a loss pulling
>     our hair out and losing money.
>     With much appreciation for all input.
>
>
>     From the Solar, Wind and Hydro powered office of Jeff
>     Oldham/Regenerative SOLutions
>
>
>     ____________
>

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