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Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 09:42pm 16 Jan 2021
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For this particular panel VMP is 30v.
You can see that power falls off far more quickly on the high voltage side. If you kept within say 26v to 32v it would be crossing back and forth right through the sweet spot. For eight panels that would be 208v and 256v with VMP at 240v.
A 48v swing sounds like a lot but it really isn't, and that same voltage range would work very well right down to very poor solar conditions.Cheers, Tony.
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578
Posted: 12:28am 17 Jan 2021
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"For eight panels that would be 208v and 256v with VMP at 240v."
Excellent, seems I am getting this closer than I thought.
I erroneously presumed that the fall off would be worse with sag and the higher voltage would be better but something else learned. It seems the timing and the setup is more effective than I thought.
Thanks for the chart too. Very useful in understanding how this works.
I would like to increase the capacitance. I have another cap bank I made up out of what I got from another GTI I stripped. The are not the same value as the ones I'm using now. Is it possible to use mis matched size caps together or do they all have to be the same?
I'm thinking both groups should charge together until the smaller one is full then the larger one will continue from there but I also realise there is a lot of electronic complexity I don't understand that may make this assumption very wrong.
I have an idea the more caps applied, the slower the charge timing can be which will still take on all the energy in peak power and also allow the panels to stay in their happy place at the beginning and end of the day when the input is lower and the panels are more easily dragged down.
I have some other inverters up there I need to scrap and get out the way as well. Some have far more useful components in them than others. Even to a dead amateur, The build quality difference is also very obvious when you get into these things and not always what I at least would expect. I might use one of the cases for this setup. I have it on some board atm but it's getting quite Bulky very quick.
For me the layout and construction is at least, and in a lot of cases more difficult than the electronic side with the simple things I do.
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 02:39am 17 Jan 2021
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As long as they have sufficient voltage rating, any caps will do. The more the merrier.
Increasing the capacitance will have zero effect on anything except how fast it cycles.Cheers, Tony.
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578
Posted: 09:24pm 17 Jan 2021
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I'll add some caps and see is that improves the power on the tail ends. May not be doing much next couple of days, have to go to the doc today for an injection.
In my eye! :0)
Not as bad as it sounds but it is painful ( and teary) to go out in the sun afterwards .
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 11:03pm 17 Jan 2021
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It will not make any difference to power transmitted or efficiency.
I don't much like the sound of that Dave.Cheers, Tony.
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578
Posted: 12:32am 18 Jan 2021
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I was thinking that more caps would allow longer timing by not filling or over filling during the peak output times but allow slower timing to get more energy ( with lower impdence on the panels during the tailing times and in overcast weather.
The counter question would be if adding caps is of no benifit, how does one conclude when they have enough? By what I have done with the lamp and the load or with an Oscilloscope?
Well it won't be the first one I have had and won't be the last either. It sounds a LOT worse that what it is, walk in the park really. I was freaking more about my vision. I knew something was off initially when my sight in that eye was way out ( kept trying to recalibrate my camera's focus initially) and I then realised I had NO focus point at all. Not an optometrist but I know enough to realise that was not good.
Turned out I have like a Pimple right in the back of my eye where the optic nerve connects. Caused by my diabetes. Distorts the convergence point of the lens and nothing is right. The surgeon is a brilliant guy, first thing he commented to me on was my size and he's not smaller which was funny but reassured me that it could be fixed and it's got much better already.
Initial fear was how in the hell does a person stay still while someone jabs you in the eye and not flinch but the guy just pulls my head back Opens my eyelid and jams it in. Less pain that doing my blood sugars and a lot quicker than giving blood.
In any case, Physical pain isn't what scares me. Emotional pain is what I'm terrified of and struggle with!
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 01:30am 18 Jan 2021
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If the capacitor is made rather small, it may struggle handling the charging and discharging current. Capacitors have a max rated ripple current, which has to do with internal heating and temperature rise. If your capacitor runs rather hot, that is not good. Add more to solve that problem.
A very fast cycling rate would theoretically increase the switching losses, but mosfets are so fast, it would not be an issue.
Going the other way, super large capacitor bank could take several seconds to charge and discharge. No real problem with that, apart from the cost of the capacitors.
Your system with five amps and 1,000uF is probably cycling around 100 Hz as a guess. Your load indicating lamp would show constant brightness. If you go to 10,000uF it will probably be more like 10Hz and you might begin to see some lamp flicker even in full sun. In very poor solar conditions, or dawn/dusk you might see a very brief flash once per second.
I suppose one advantage of a very slow cycling rate mghht be that under poor solar conditions, charging will be extra slow, and you can watch the voltage slowly climb and dip on a multimeter. That would be very convenient for setting the system up initially.
On the other hand, if you have an oscilloscope, a much faster rate will be a lot easier to see on an analog oscilloscope. Anything slower than abut 10Hz becomes difficult to read, the screen just briefly flashes each sweep. A digital oscillosope would be much nicer at any speed, because the waveform is stored and appears continuously on the screen. Edited 2021-01-18 11:43 by WarpspeedCheers, Tony.
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578
Posted: 09:01am 18 Jan 2021
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Thanks again Tony. I have a mystery cap bank I put together that's smaller than the one I'm using so I'll put it on tomorrow and see if I can observe any Differences with the voltage readings and the lamp with the load. Next one I put together I'll be sure to mark the capacitance and voltage before I tape it all up like a bunch of powergell.
Had the Eye done today. Honestly, the waiting 1:45 for the specialist for a 10 min review and another Jab was 100X worse than the actual procedure which was nothing at all. My arse is still numb from the most uncomfortable chairs ever made.
I like the guy, nice fella but when he brought me in and commented on what a mad house it was today, I couldn't help but have a passive aggressive jab at him and say "Well you work by appointment, I'd be having a word to my secretary and telling her to allow more time per patient as you are always run off your feet and don't get any breaks. My secretary always knew what time to allow for my appointments so the clients weren't inconvenienced and I wasn't running round like a headless Chook."
He just said Normally not this bad. I said shouldn't be this rushed for you ever. WTF is it with doctors that they and people think it's acceptable to have an appointment that they can't even keep within an hour or more, EVER!
Anyway, seems my eye has made a recovery he sees only 1 of in about 300 he said which seems beyond belief for my usual luck. I was half expecting him to say there was some complication and they would have to remove a Toe or something. Perhaps this will be the last injection I have to have. he was in 2 minds about giving me this one at all. He said it was probably best to play on the safe side which I think was a very professional way of saying, "I want to hit you up for another $550." Doesn't want to see me for 3 months which is a good sign, especially for my bank balance.
I'll be happy to go back out tomorrow for some more playin..... serious research.... Maybe with 2 pairs of Sunnies or my welding helmet.... which would be quite viable actually being an auto darkening type which I can turn down pretty dark before it Fully activates.
Never thought, I could have worn that today instead of the stupid face nappies you have to put on like a compliant sheep here atm. Least I have no trouble breathing in the welding mask.
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 10:34am 18 Jan 2021
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I used to work in a large teaching hospital, and I have never cared too much for doctors or how they treat their patients. Fortunately my health has always been exceptionally good, so I have been spared from the medical profession.Cheers, Tony.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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