Recent Posts

51

Renewable Energy Q&A / Re: Max winding temp

« Last post by lighthunter on June 14, 2022, 06:26:59 pm »

Update:

Thanks again Pete for all the ideas and thoughts on this one. All attempts to adjust the volt/amp curve via vfd programming failed as the OEM disallows it. Weve yet to get any real support from those people.

 The compressor has been running fine for a while now. I drilled a hole near the bottom of the end frame and put compressed air to it so it blows cool air through the cage out the cover of electrical box. A co-worker drilled the fitting a bit larger as the cooling requirement was higher than i had anticipated. It takes around a 6hp efficiency hit just to cool it but it works. Runs about 175F now. Whats difficult for me is knowing exactly whats ok? A different unit had oiltemp that reached 221F today. Pressure washed cotton fuzz from radiator and now at 196 where thermostat regulates it. Maybe its fine for winding temp to be 250F no one i know will go there and articles written about it tiptoe around the subject. Oddly most manufacturers do not put temp sensors in windings yet a common house fan includes this as a safety device. A thermal cutoff or tco. As i write this im reminded of an event years ago... 1998... how time has gone... when a laser roots blower also siemens motor, failed due to a temp sensor in winding. I jumpered and machine ran, i ordered a temp switch in a T0220 package and inserted/epoxyed into winding at end of motor seems like i started at 110C and kept having to order higher ones till i got one that didnt trip under normal circumstances. Seems like the number was 115 or 120C when i finished and that one ran for years that way. So by that info i can set this at 250F and reduce the orfice size to maybe 4HP of cooling. Of course an air booster in reverse trading pressure to volume would reduce the flow requirement again.  Anyone else agree i can increase thermal trip point to 250F or 120C?

I kinda feel stupid i forgot the eqperience i learned back then about winding temp.

Perhaps i better ask the elder gentleman what class wind wire he used for this one.

Its not an ideal solution but it is a solution and it does run welll now. Anyone have an idea on a moisture sensor for air line. I will need it to fault on humidity as moisture will kill windings too. So far our dryer is flawless but theres no feedback to stop anything if it doesnt remove all moisture.

Hope everyone is doing well, i havent had much time to post as garden, work and other odd jobs have been over the top lately.

52

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

« Last post by solarnewbee on June 04, 2022, 02:28:40 am »

I meant to say put one battery on top of the other. They are sealed so no checking levels.

On the other subject, I have a short across the battery connections on this inverter board. Thought it might be the caps or the mosfet over by the egs board but not so. I reckon I was sold at least 1 bad hy4008. Jumped the gun and didn’t get out the tester before putting them in. I am officially trashing this board because I would have to desolder every single fet. No thanks.

Thanks for your help tho. Adios!

53

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

« Last post by Pete on June 03, 2022, 03:12:21 am »

Hi Solar not sure what you mean by " can I stack the VRLA batteries  2 together, if you mean parallel two banks then sure.
It is not the greatest practice but from what I read up to 4 banks is not too bad to parallel.
I have had heaps of parallel banks of Flooded batteries in the past, no real problems.
As long as a cell doesn't short out then all is good. And as long as the battery banks are similar age and capacity.
Hope it all goes good with the repairs when the parts turn up.
Pete

54

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?

55

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

56

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

57

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!

58

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

59

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.

60

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