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oztules
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Posted: 13 May 2017 at 7:31am | IP Logged Quote oztules

Struggling to find time to scratch myself at the moment, so no have not done so yet.

New boards will be working tonight or tomorrow..... testing seems good thus far.

Very nice to see your unit is working without fuss.... well done.


..........oztules

Edited by oztules on 13 May 2017 at 7:32am


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Madness
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Posted: 14 May 2017 at 5:32am | IP Logged Quote Madness

Just been trawling the net for information about IGBTs and came across this information about how to connect an Aero-sharp to your computer.

Someone may find it useful you can see it here.

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Posted: 17 May 2017 at 10:46pm | IP Logged Quote Madness

I have now set up the 5KW of panels I recently bought, these have replaced a 2.8KW array that I had in the location.




I have 9.5KW of panels now, as yet I have not had a really sunny day since setting up the new 5KW array, most I have seen is 3.5KW on the GTI connected to the new panels with about 3 KW back feeding through the inverter.

Now I need to work on controlling the excess power I am getting on sunny days. I am very happy with how the inverter is just running without fuss both powering the house and back feeding charge into the batteries from the GTI.

Edited by Madness on 17 May 2017 at 10:49pm


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Posted: 18 May 2017 at 9:15am | IP Logged Quote oztules

That may lend itself nicely to fet driven string shut down... ie sequentially shut off one string at a time etc based on battery volts and current.

I am crying in my beer looking at what you mainlanders get for $700.... wow.



..........oztules

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Posted: 19 May 2017 at 2:43am | IP Logged Quote Mulver

Madness wrote:

Now I need to work on controlling the excess power I am getting on sunny days.


This has been my research topic for the last few weeks! I am only at the toroid winding stage but Im trying to plan ahead what ill do.

I remember oztules stating he can waste ~75kw on a good day, due to low loads and plenty of sun!GTI's turn off etc.

This started me thinking what can we use this power on! My thoughts ATM...

Sun comes up batteries charge back up and then you have excess to burn.

Turn on hot water, modulate a SSR to consume the excess until its not needed or there is too much excess.

Thats pretty straight forward nothing complicated.

Arduino Battery Voltage Controlled Relays

Next biggest consumer is Heating/Cooling! Im in SA so its AC in summer and wood fire in winter, problem is the wood fire is terrible for the environment, for my asthmatic wife, and cost me 2k a year in wood. As much as we love the wood fire long term i would like to only use it occasionally not as primary heating.

So in winter (we plan on renovating) Underfloor radiant heating in as many places as possible and wall mounted radiant heating elsewhere. ALL controlled via the excess power available. With intent to heat soak the house (while not in it) to hold the heat in the slab and walls etc. We have a mud brick house so it holds its temps for up to 3 days before outside extreme temps starts to be felt inside.This will hopefully be enough to have the house comfortable and not require heating overnight.

So far pretty straight forward I think

Next is Summer the dreaded AC, I plan on installing a ducted inverter AC and i would like to be able to control it in the same manner as heating! Vary the power is consumes to the excess thats available. Problem is AC's are way more complicated than an element.

But i stumbled on the below thread.

Daikin SKYFi Api


They gain control of the AC via sniffing out the IP traffic to an web based control.

This to me seems reasonable that we could monitor, the outside temp, the inside temp, and the excess power available. Then send commands to the AC to various set points dependent on these variables.


Taking it a step further if you logged the outside temperature, you could swap automatically between heating and cooling dependent on the average temperatures.

And if you had WAY to much excess power you could run the AC on heat mode and the floor heating at once!

Sauna anyone?

Edited by Mulver on 19 May 2017 at 2:51am
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Posted: 19 May 2017 at 4:36am | IP Logged Quote Madness

Whoops, I forgot about that Arduino thread, I need to complete it.

Here is my thoughts regarding the extra power and what to do with it.

At present, I have 2 Midnite charge controllers that have 2 auxiliary controls each, one is simple on off with set points and the other is PWM. Eventually, I will be replacing the Midnites with a DIY controller that is based on an Arduino, this would allow a lot of flexibility.

I use the on off AUX of the Midnite CC to switch on my HWS element when absorb or float voltage is reached for 30 seconds and will stay on until 10 minutes after the the voltage falls below the set point. I was running this previously off PWM which does not work so well with the GTI connected to my DIY inverter.

What I have considered is to also run the AC with the on off state and a time delay. I think most AC's will come back on to the last state is was in if the power is disconnected. If you leave the AC set to auto and an appropriate temperature it could come on and run, if there is plenty of power it will stay on, if not it will turn off again after the delay time has elapsed.

This is all okay but eventually you will find yourself in a situation where you still have too much power and need to throttle back the panels. If my solar HWS temp is down after a day or 2 of cloudy weather it soaks up the extra power for a day or so but the thermostat clicks off and the battery volts climb too high with the 5KW GTI.

What I am working on is using one or 2 of the IGBT's and the board that attaches to them from the Aero-Sharp Inverters to control the connection from the solar panels to the GTI. By using PWM to control this it could supply the right amount of power required and no more. I would still try to utilise as much power as practical and still divert power to the HWS and AC.

I may be completely wrong here (I am no electronics guru, just feeling my way around in the dark) but if I connect the panels to the IGBT as per this diagram I can control both PV array's to the GTI with a bank of capacitors across each output to smooth out the DC.


This is the opto isolator board that comes with the IGBT


The isolator chips are 2017-05-19_042919_AV02-0867EN_DS_HCPL-4504_2014-01-070.pdf 4504


I think all need to do is supply the correct voltages to the PCB and 5V across pins 2 and 3 to turn it on the IGBT. As yet I have not worked out the supply voltages but I see pin 8 of the isolator require 30V.

The Arduino circuit from the thread mentioned in the previous post could be used to control it and it will be very easy to program charging times and voltages for absorb and float with the Arduino microcontroller.






Edited by Madness on 19 May 2017 at 4:44am


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Posted: 22 May 2017 at 11:21am | IP Logged Quote Mulver

Very interested in how you go with that Madness!
I was playing with my growatt 4200 gti and an inverter generator. Testing for the next blackout!

Anyway, what I noticed was even though the sun was shining well on the 1.5kw of panels when the gti connected to the genny. It slowly ramped up the power.... not a sudden shove of power I was expecting. The genny just slowly backed off as the gti ramped up.

I'm assuming it's doing its mppt thing up to the best it can find.

Surely someone (much smarter than me) would be able to trick the gti to control the power.

I assume it uses reference voltage to do calculations could we maybe intersept and modify.

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Posted: 22 May 2017 at 12:38pm | IP Logged Quote Madness

I have Wednesday to myself so will work more on it then, been catching up a little on other things that were forgotten about with the inverter build.

I did see somewhere a SMA (could be wrong) AC coupled system that stopped the GTI by varying the frequency of the OGI to cause the GTI to shut down due to the frequency being out of range. Seems a bit of a clumsy way to do it especially for a manufacturer.

One possible way to fool the GTI is to play with the current\voltage sensing on the output, that may cause it to throttle back a bit but it may not get the point of shutting it down. The MPPT itself would be would be all software and hard to figure out even if you could get into it, possibly playing around with it's sensing of PV voltage could be a possibility too,

Today was mostly sunny and once again I was making more power than needed even with the hot water element on, tomorrow the HW will probably shut down due to being quite hot already.

I have a spare inverter generator with a blown inverter, I have thought about just using its generator with a rectifier and capacitors to feed DC into a GTI.

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Posted: 22 May 2017 at 12:44pm | IP Logged Quote Madness

oztules wrote:
That may lend itself nicely to fet driven string shut down... ie sequentially shut off one string at a time etc based on battery volts and current.

I am crying in my beer looking at what you mainlanders get for $700.... wow.



..........oztules


I have seen a few sets of 5KW for $1,000 but that is the first time I have seen them that cheap. Just sheer luck, I had even deleted the email from Gumtree for them before reading properly. Something said hang on I need to look at that email.

That combined with the $5 5KW GTI from the tip that is running perfectly is just a fluke that I will probably never repeat.

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