Wiring for Hyper VOC

[Kent0]

Thinking about a system design for an owner that wants the PV array located a 1000 feet away. We'd need to push the voltage to keep the wire cost down. Considering a Classic 250 with strings of 6 Sharp 240 modules. These will put a Classic 250 into hyper VOC mode when the temperature drops below 20°F. It'll happen several days every winter.

What happens if the owner opens the Classic's battery breaker while it is in hyper Voc mode? I know you should open the PV array first, but what happens if it is done backwards and the battery is opened first? Should the input and output breakers be ganged? A three-pole breaker?

[Westbranch]

Kent, can you design the wiring such that the system will not be greater than VOC, ie use V loss by using a smaller wire to stay < HypV?

[Kent0]

There is no current, and no wire loss, until after the Classic is awake and operating. Even at 16 amps, with the array 1000 feet away, 2 AWG gives 3.5% loss or about 6 volts. So even at full power there would be little relief from the high voltage.

With strings of six modules Voc = 272 at -35°C, that's a record low. Voc = 250 at -8°C, that'll probably happen a couple dozen times each winter and, except for a few days, it will warm above that by 10:00.

[Westbranch]

Hmmm, looks like with that panel you need to drop to 5 per string, to ~ 230v or ~223 v after losses. any other panels you can use with different specs?

[Halfcrazy]

Kent
In Hyper VOC the Classic's internal relay will be open so as soon as the battery breaker opens. A triple ganged breaker would be sweat and seems like it should work well but not necessary.

Ryan

[boB]

What happens if the owner opens the Classic's battery breaker while it is in hyper Voc mode?

Nothing should happen because the Classic is NOT pulling down the PV nor drawing PV current when in HyperVoc mode.
The Classic will just turn off and the lights on the Classic will go out.

Now, if the Classic is operating and bringing down the PV voltage and the battery breaker is flipped,
the PV voltage will go up as the Classic brings the battery voltage into Absorb, and the battery voltage
on the Classic battery terminals will rise above set points because of reaction time, (for a moment),
but it shouldn't get very far above battery set point as there is  very fast responding voltage reading
in software that will try to quickly turn it all off.   We went through that scenario quite a while ago
and nipped that one (hopefully plenty good enough !)

Regular solar mode opens the input from time to time (quickly) and so it isn't too likely that the Voc
would be allowed to rise very far into the HyperVoc region during those intervals for it to get very
high as the module temperature drops.

boB

[Kent0]

Ryan and boB,

Thanks for your replies. It's amazing how fast a transistor lets the smoke out. Since the hyperVoc mode is a new concept, I want to know it is going to be as bullet proof as the normal operating mode.

[niel]

one solution is to cheapen the wire to the point that the resulting voltage drop would cover the increase from the pv. kind of counterproductive though.

[mike90045]

use V loss by using a smaller wire

or

cheapen the wire

Will not work.   You need amps flowing, lots of them, to get the losses in the wire.  As the sun pops up, and the classic wakes up, there is no flow/amps, till it sweeps the array, and loads it down.  Till it sweeps and selects a MPPT point, there is no amps, and you have full array open circuit voltage on the classic.

[niel]

another option could be a diversion load triggered by either the temperature or the voltage that would be just enough to hold it below the hyper point.

[boB]

Ryan and boB,

Thanks for your replies. It's amazing how fast a transistor lets the smoke out. Since the hyperVoc mode is a new concept, I want to know it is going to be as bullet proof as the normal operating mode.

If  one follows  "The Rules of HyperVoc",  (I kinda like that one ! ),  it has not let us down yet.
For those who don't know what HyperVoc is, it means that you can add the "nominal" battery
voltage to the input of the Classic  model.   For Example, a Classic 200 and a 48V battery bank
can withstand 248 Volts on its input, although the Classic 200 will not turn on and operate
at 201 voltsand above.   Classic 250 and 24V battery, good to 150 + 24 = 174 Volts maximum.

48V is the max we'll spec for HyperVoc though.

Much above these values and we may see smoke. And we know that
smoking is bad for you and your Classic's health....   HyperVoc during
pregnancy has not been tested.

boB

[niel]

i certainly know what hypervoc is, but i thought he wanted to keep things going rather than shut down due to hvoc. i guess it won't be as big of a problem as he may think either because when it is the coldest it is usually at the break of dawn and there is little strength in the sun at that time. being it is hitting the pvs somewhat the sun will slowly start to warm them up too before the current really ramps up and hopefully that current will pass on to the batteries/loads and help keep the voltage down a tad. it may not warm up fast enough at times to stop the voltage from hitting its high point if batteries/loads can't bog it down enough, but i don't believe it would be too long in hvoc with possibly a rare occasion.

no need to worry boB as the rabbit didn't die.

[caldoverde]

If  one follows  "The Rules of HyperVoc",  (I kinda like that one ! ),  it has not let us down yet.
For those who don't know what HyperVoc is, it means that you can add the "nominal" battery
voltage to the input of the Classic  model.   For Example, a Classic 200 and a 48V battery bank
can withstand 248 Volts on its input, although the Classic 200 will not turn on and operate
at 201 voltsand above.   Classic 250 and 24V battery, good to 150 + 24 = 174 Volts maximum.

? Don't you mean Classic 250 + 24V battery = good to 250 + 24 = 274V max? This is why I bought the 250, so I'm hoping that was just a couple of typos?!

I'm here on the computer now going through the manual again trying to figure this thing out but struggling a bit because although I understand the basics of renewable power generation, it's ... well, it's just the basics.

We got our replacement 250 just over a month ago for our hydro but with the severe drought here, we've been down to a trickle of water and no opportunity for testing. We installed it and set it up with the system parameters, but then left it turned off. We just had a thunderstorm so as soon as the surge came down the stream I was up in the battery house to switch on and see what was what.

The initial input from the high voltage alternator (Hugh Piggott 1kW axial flux design) was ±260V and the Classic 250 was flashing up Hyper VOC, so I waited it out until the initial surge was through and the voltage was down below 250. Once it was, I was no longer seeing Hyper VOC flashing, but in hydro mode, with the default settings, the controller was just switching itself continually on and off again and not taking the load, just as it had at the other end of the scale when we had barely enough water to make cut-in voltage. I tried the wind mode, which at least put the alternator under load but pulled the input down to ±90V giving me just 15-16W (24V x 0.6A) which seems like a pretty hefty loss to take, especially considering our Outback Flexmax 80 managed to make 21W when it only had 140V to play with instead of 250V. But I'm guessing this is all down to what parameters are set for each mode?

I haven't got the latest firmware upgrade because a) I don't have a PC, and b) I'm wary of taking a beta release when I don't know my way round this machine yet. I'd really like to get the controller set up properly since we've a few more thunderstorms forecast for this month and it would be good to see what it can do, but after looking through the manual my mind is now thoroughly boggled by stuff I don't really understand the implications of and I don't want to break anything.

Would you nice people be able to talk me through this?

[boB]

If  one follows  "The Rules of HyperVoc",  (I kinda like that one ! ),  it has not let us down yet.
For those who don't know what HyperVoc is, it means that you can add the "nominal" battery
voltage to the input of the Classic  model.   For Example, a Classic 200 and a 48V battery bank
can withstand 248 Volts on its input, although the Classic 200 will not turn on and operate
at 201 voltsand above.   Classic 250 and 24V battery, good to 150 + 24 = 174 Volts maximum.

? Don't you mean Classic 250 + 24V battery = good to 250 + 24 = 274V max? This is why I bought the 250, so I'm hoping that was just a couple of typos?!

OOOOopppps !!!!   YES, you are absolutely correct !   I did make a typo.

250V + 24V = 174V max

Sorry about that !

I'm here on the computer now going through the manual again trying to figure this thing out but struggling a bit because although I understand the basics of renewable power generation, it's ... well, it's just the basics.

We got our replacement 250 just over a month ago for our hydro but with the severe drought here, we've been down to a trickle of water and no opportunity for testing. We installed it and set it up with the system parameters, but then left it turned off. We just had a thunderstorm so as soon as the surge came down the stream I was up in the battery house to switch on and see what was what.

The initial input from the high voltage alternator (Hugh Piggott 1kW axial flux design) was ±260V and the Classic 250 was flashing up Hyper VOC, so I waited it out until the initial surge was through and the voltage was down below 250. Once it was, I was no longer seeing Hyper VOC flashing, but in hydro mode, with the default settings, the controller was just switching itself continually on and off again and not taking the load, just as it had at the other end of the scale when we had barely enough water to make cut-in voltage. I tried the wind mode, which at least put the alternator under load but pulled the input down to ±90V giving me just 15-16W (24V x 0.6A) which seems like a pretty hefty loss to take, especially considering our Outback Flexmax 80 managed to make 21W when it only had 140V to play with instead of 250V. But I'm guessing this is all down to what parameters are set for each mode?

I haven't got the latest firmware upgrade because a) I don't have a PC, and b) I'm wary of taking a beta release when I don't know my way round this machine yet. I'd really like to get the controller set up properly since we've a few more thunderstorms forecast for this month and it would be good to see what it can do, but after looking through the manual my mind is now thoroughly boggled by stuff I don't really understand the implications of and I don't want to break anything.

Would you nice people be able to talk me through this?

OK, 260 V is a piece of cake for the 250 so you're good there.

As for dragging the hydro down to 90V, I'm not sure why that is but lets find out what version of software is in your classic
so we can tell what peculiarities it may have in hydro mode.  The very first hydro mode was kind of buggy in a way or two
but we might be able to make it work.

To find the version, go to main STATUS and press the STATUS button a few times until the date of software
comes up for the Classic and MNGP (remote) and note this.

Which hydro mode is it in ?  Manual ?  Sweeping every 3 or 4 or 5 minutes ? Twiddle-Dither mode ?

BTW, the latest Twiddle-Dither mode in hydro has been slowed down some but not released yet so you may eventually
want that update if that mode will work good for you.

I would try Manual MPP V  mode first so you can set the operating voltage yourself.  When in Manual MPP V mode,
the Sweep Depth adjustment should go away.  When in other modes, the MPP V  adjustment will still be on
the display, but will not actually mean anything except in Manual MPP mode.

boB

[caldoverde]

Thanks boB! Unfortunately the storm knocked out the internet for a while and it's 11pm here now. Will find out the version tomorrow and report back. Will probably have to wait for more rain before going further as the stream is back down to a trickle again.