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51

Users Projects / Re: y Philippines Retirement Solar Off Grid System

« Last post by solarnewbee on June 03, 2022, 01:28:52 am »

Found that a IRF640 fet was shorted. Removed it and the current went to zero. Have new ones on order. Extras in case something goes wrong again. The diode mur680g seemed ok. I have a feeling it will come to life when a fresh fet  is installed. Some people power up using an incandescent light bulb to charge the caps slowly. Hard to find in a country that outlawed incandescent bulb sales and now florescent bulbs too.

On another subject I am replacing 1 bank of lfp’s with 4. 200ah VRLA batteries. The lfp’s are running on 15 pieces and appear to be giving out about 2/3 ah they used to. I replaced a cell and the new cell immediately went bad and bloated. I bought 4 new and so 1 out of 4 was bad and I installed another. That one goes bad. I call the factory. They tell me that since my internal resistance of the old batteries is so far apart from the new battery that this is what happens. Stop and don’t put anymore. It’s like changing tires on a dual tire truck if you don’t change both tires the new one will fail early. Surprisingly the bank charges up to 57.8 volts then settles to 54.3 ish most days. Unknown to me the breaker to the good bank had tripped and wasn’t being charged. I was getting 9 hours out of the bad bank. These are 200ah batts. Just weird stuff.

Question, I am short on space, can I stack these VRLA batts 2 together?

52

Users Projects / Re: y Philippines Retirement Solar Off Grid System

« Last post by Pete on May 29, 2022, 03:55:09 am »

Hi Solar from memory, I started with a 20 watt 10 ohm resistor in series with the power supply to my board, then after I checked the current drain and gate drives of the mosfets I reduced it to 10 ohm then to 5 ohm.
When the board still ran with that I connected the supply directly to the board.
As I said the big capacitors need to be removed or they store enough power to blow mosfets if there is still a problem.
Usually when mosfets blow they take out their driver transistors and sometimes resistors too.
Make sure that they are all getting a clean gate drive when you fire it up.
If it all runs good then replace the caps
pete

53

Users Projects / Re: y Philippines Retirement Solar Off Grid System

« Last post by Pete on May 28, 2022, 05:48:04 pm »

HI Solar, I used Oz's ideas when repairing my inverter boards.
It requires that  you take out the big capacitors in the centre of the heatsinks. This reduces the inrush current and prevents the caps from supplying power to the mosfets and blowing more up
Then use a resistor in the supply line to limit the current (in case there is a shorted mosfet).
It will need a transformer connected as there is a feedback loop there that needs to see a return.
Good luck
Pete

54

Users Projects / Re: y Philippines Retirement Solar Off Grid System

« Last post by solarnewbee on May 28, 2022, 05:28:50 am »

Howdy Pete,

I finally got around to repairing my AliExpress special, inverter. Changed the egs board and all the resistors and diodes. Also replaced the small caps and tip41/42 transistors that blew. I tried powering up with a variable power supply but no joy. It goes into cc mode and pulls the voltage down to 2 volts from 48. There is a mosfet  on the end near the egs marked 12v on the board irf640n. Another maybe diode mur860g on the board u860g on the device.

Does the transformer have to be attached for it to fire up? I remember you saying there was a way to do it with a resistor or something but I can’t find it. Pics below. 4 views since none of these boards are ever completely the same.

Cheerio!

55

Users Projects / Re: Going off-grid in Idaho

« Last post by Pete on May 10, 2022, 05:01:24 pm »

Hi Doc, thanks for the reply. I am only adding the new panels because I got them really cheap. They are a backup for the times that we have heavy cloud cover.( which happen a bit here on the mountain). So far we have heaps of power but I just want to make sure that the batteries come up on cloudy days in winter too.
I read the article OZ put up about his GTI connection and also looked at his home made PWM controllers. Pity he is not around to quiz and get the rest of the story.
Take care
Pete

56

Users Projects / Re: Going off-grid in Idaho

« Last post by dochubert on May 10, 2022, 10:09:25 am »

Hi Pete,
I did try hooking a grid tie inverter to my powerjack, just to see how it would do.  Didn't go so far as building safety circuits to regulate it.  Just watched it closely.  Didn't have enough solar hooked to the grid tie to worry too much about.
Anyway, it worked ok, but seemed to me to make the system more complicated and possibly unstable than it needed to be.  I can power the house with the powerjack just fine, and it's (usually) trouble-free.
As for those safety cutouts, my understanding from those who tried it, was to not disconnect the gti from the powerjack, because when it re-connects you get the 5 minute startup delay of the gti.  Instead you interrupt the solar to the gti, which leaves it connected but not producing.  Same result but smoother operation with no 5 minute deadtime each time it throttles back.  Same as if clouds blocked your panels.
I think lighthunter did some work on those things, with good results.

57

Users Projects / Re: Going off-grid in Idaho

« Last post by Pete on May 10, 2022, 02:39:28 am »

Good to hear you are still about Doc. Seems the site is very quiet these days.
I am guessing that some of the old timers are no longer with us on this planet.
Just wondering whether you use Grid tie inverters as a mini grid.
I am thinking of using one I have in the shed ( we have no grid power) but just wanted to hear how others have got theirs to work and how they regulate the output into the batteries.
I am thinking of using a small charge regulator to measure the battery volts and to open a relay to disconnect the GTI from the main inverter output when the batteries are charged.
I did see some stuff that OZ was working on when he was about but never saw the end result. It is hard to get through all the iterations of the boards and circuits to see which one actually worked.
Anyway hope all goes well with snow shovelling, it is coming into winter here so we will have a bit of snow, we dont' get much though
Cheers
Pete

58

Users Projects / Re: Going off-grid in Idaho

« Last post by dochubert on May 09, 2022, 09:00:46 pm »

Today, the 9th of May, we had heavy snowfall that lasted hours.  I found myself at just past noon shoveling snow off of my solar panels. IN MAY!  I needed them today too, as grid power went down around 8am and didn't come back until sometime around 1pm.  We were already on battery/solar and have been since late March so I didn't realize the grid was down until my wife came home from her volunteer work at the library and told me.
Sometimes it's nice to be prepared for the worst.

59

Renewable Energy Q&A / Re: Max winding temp

« Last post by Pete on May 07, 2022, 09:53:06 pm »

Hi LH, one other thing to check if the motor is ever apart again is the Rotor.
Squirrel cage rotors do fail.
The bars in the slots usually break at the rings that connect them together at the ends.
This causes the motor to hunt and make strange noises, they sound like they are trying to get up to speed but can't quite make it so they emit a strange humming noise as they run.
I once walked into an autoelectric shop I worked at a few years earlier. They had a 100hp motor that they could not find anything wrong with, They were just about to start chopping the stator windings out when I looked at the rotor.
The rotor had copper bars that were silver soldered to a brass ring. Sure enough some of the bars were broken.
I managed to stop the fellow with the air chisel just in time. He was just about to start chopping the stator winding up.
You could always slip some thermistors into the windings if you wanted.
Unfortunately as the controller is setup, the motor will probably just keep tripping the thermistor relays anyway.
Good luck
Pete

60

Renewable Energy Q&A / Re: Max winding temp

« Last post by lighthunter on May 07, 2022, 07:09:03 am »

Hey Pete,  yes this inverter is programmed to ramp voltage with freq/rpm. From memory, ive seen it down to 120v/phase at the minimum freq. around 700rpm.

We had chaos on thurs and no work on friday due to a computer network outage.  I will get the voltage reading at 45.75hz on monday.

 Since the slippage is (normal) and current is high, This much points to volts being too high at that particular frequency? Am I understanding right here?  Assuming all other aspects of the motor and load are correct of course.

My reasoning for doing the rpm/slippage test was to determine if for some unknown reason the shaft was loaded too much or volts were too low, i thought there would be more slippage. Maybe my equipment was not accurate enough to draw that conclusion.

I cant thank you enough for your input on this. Ive just never really had to mess with induction motor behavior before. The only other time it got close to this was a new  fan/filter unit kept tripping 20A 480v breaker like once a week. (I dont install this stuff, just try to fix it) so this went on, company was crap to zero support
from italy i believe. Then burned up disconnect switch and breaker. I got those replaced under warranty. Motor then burned weeks later. I had it rewound because they couldnt supply new one quick enough. I called. the motor rewind guy and gave him measurements and he said its gonna fail again if you leave it that way, so i ordered a new motor next size up thinking this would cure problem now the electrical supply was too small to handle it so put a vfd on it and dialed it to 50 hz and its been about 8 years since weve had trouble with it. Im pretty sure the company fitted the wrong centrifugal fan blade in it causing the grief.

You dont usually question the design of this stuff but this was a clear example where they got it wrong. Because the motor on this compressor failed under warranty and twice since leaving all things OEM i think that proves thats the case here as well. They never bothered to put a temp sensor on motor. I could just remove it and push the button and walk away, let it cook. Who knows it might last another two years. Ha!