[RE-wrenches] Using a Midnite Classic for Hydro

boB at midnitesolar.com boB at midnitesolar.com
Thu Mar 19 12:18:18 PDT 2015


I forgot to mention one basic thing in the last email...

I mentioned how the CC reduces the output current and output voltage
but what I didn't mention is that when the battery gets fully charged, 
and/or
the battery side can not use the power from the solar or hydro or wind 
source,
the controller opens up the input letting the turbine free-wheel.

It may either raise the input voltage as high as it can go to keep the 
battery voltage
and current in check, OR in your case it went above 250 volts and then
to Resting which is OFF.

The primary purpose of the CC is to keep the battery voltage from rising 
above
the charging set point and to give the battery maximum power/current when
it needs charging.

Most MPPT charge controllers operate this way.

boB


On 3/19/2015 11:57 AM, boB at midnitesolar.com wrote:
>
> 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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