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Author Topic: single wire low RPM cut in. Suggestions...  (Read 668 times)
mike90045
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« Reply #30 on: November 08, 2017, 07:55:54 PM »

The problem without having solar you have to run the internal combustion engine a long long time for the final 20% of charging of the batteries. If the batteries don't reach 100% full charge several times a week they start to sulfate and then you lose capacity and the batteries can be ruined within a couple of months.
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glort
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« Reply #31 on: November 10, 2017, 06:58:01 AM »

Or perhaps pull the regulator out of the alternator and feed it into a solar MPPT charger such as this?

https://www.invertersupply.com/index.php?main_page=product_info&cPath=1304_258_260&products_id=1030

That way when I go solar I can dual purpose it, when the sun isn't shining I can disconnect the solar and hook up the car alternator to charge the bank.


Right now the site is down so I can't see what you are talking about.  As far as taking the reg out of the alternator, I'm guessing that you may be trying to couple it to a grid tie, High volt input  inverter which kicks in at 90-120V? If not and it's 24V inverter, much the same thing.

I have tried MPPT inverters with alts and it was not successful for me and I doubt it would be without some sort of electronic regulation additionally.
What happens is an MPPT tries to find the sweet spot of the alt just like it does with panels.  It will up and down the amps to try and find where the most watts are. That's what they are designed to do, keep testing the water as it were.
 What happens on an engine driven alt is the inverter will pull to it's max capacity which pulls the engine down. I was using a capeable engine for the alt which would turn it at full output constantly with a reasonable margin. IE, it wasn't flat out, maybe 75-80%, but the MPPT's seem pretty sensitive and as soon as the watts drop which will happen with a mechanical  governor, the Mppt lightens up and the revs and volts pick up. Seeing there is now more apparent power, The mppt will increase the load again trying to pull the Volts back to it's nominal sweet spot, power drops, inverter backs off and you go into this endless seesaw effect.
I tried caps and base loads and all sorts of things and I could not get it to change  which is the logical outcome given the way teh MPPT is designed to work.

I tried the same thing with a petrol generator with AVR and a rectified output, same thing. MPPT inverter had it hunting all over the place and the inverter would drop out in a few seconds due to the variation which it sensed as a fualt condition.

The only ( simple ) way I could see it working would be to have an alt capeable of say 2000W and the inverter only rated to 1500 say.  The engine would be the bigger the better with heavy flywheels for better reactive power. ( Less slowing when a heavy load hits)  The alt I had was over the Mppt's capability by  safe margin and even though the engine could carry full load of the alt, it doesn't take much to get SOME variation and the mppt seemed sensitive to this. Even with solar panels in clear midday sun, I can still see endless variation of  at least a 50V range all the time. Usualy not as much as 50V but will certainly move that much regularly but NEVER constant on an output of around 2KW and well over driven on the panel side as well.

If you are talking about a 24V alt and a suitable MPPT inverter going to the batteries, can't see it being any different. MPPT is always going to be ramping up and down increasing the load and backing off and being electronic will be faster than an engine can respond be it mechanically or electronically governed. You'd want a 3208 Cat or a 6V53 jimmy driving a 5Kw alt to be stable enough I reckon, something 100X overkill.

MPPT is a waste for this setup.  If you are going for a grid connected unit you probably don't have a choice as all solar inverters I have heard of are MPPT.  What you really want in this setup is actually a PWM type controller . One that you can dial up the output and if the  input is constant, so will the output without hunting around.  MPPT is only really needed for solar panels that may get shaded or clouds etc. where the PWM reduction would be unlikely to be the most efficient. When you have something that going to produce the same power at the same speed for the same load, PWM is every bit as efficient and in this case, most likely the difference between workable and not.
I would expect if you took the reg out of an alt with a Mppt controller attached, it would be even more unworkable. The power curve would be even more all over the shop and the Mppt would go nuts as would the engine govenor trying to keep up with the load that was all over the place. The Govenors simply aren't designed for that and if you were using a small, lightweight petrol  engine...... Pffft! Forget it!
I tried that ( at length) with a big electric motor converted to a generator. Set up a C2C conversion with capacitors and 3 phase 100a rectifier to turn the 3 phase supply to single phase and ran that into the grid tie solar inverter.
With a 6HP diesel, even with the 5.5Kw engine that weighed 50Kg, the variation was too much and the inverter would trip out on low input as it dragged the diesel right down.

Next bright idea was to use a bigger diesel, a substantial 12HP that has a lot of grunt and about 3 times oversized for the job.  First I set up to get a stable voltage with a mid range load.  Revs vary output on this sort of setup.  That done, I put on the inverter. It kicked in, fairly gently at first then sensing volts were still in range it ramped up. pretty fast.  Even teh big engine with teh big IMAG couldn't keep up, I watched the volts fall on the multimeter  then the inverter let go and the volts shot up..... way over the inverters rating ( Way over!) and must have defeated its protection and cooked it.  Also lucky it didn't blow the shit out of the 400V rated caps in my face and arc out when my multi-meter literally blew itself off the floor as I saw the last read out at 1280V.

I'm not sure the way around this for you.  If you can find a PWM inverter, which I doubt, you may be OK. Other than that, I think you are going to have to go for a setup for the engine generator and another for solar.

Don't mean to sound a killjoy or a bitch but to me this is getting way over the top. Sounds like you have a lot more money and earn a load better than I do but I can't see the economics of it.
You want backup power, fine, go get a Genny and a transfer switch and you are good.
You want to shave that $12 Kw fee every month, I get it. I would too.

Thing is what I'm seeing here is you are going to spend FAR more than you could ever recoup on that. If your high is $60, how many month is your investment and everything else going to take to pay off?
The answer is more than the life of the batteries and most likley everything else as well. And don't forget, those batteries are going to be good for about 500W for 4 hours.  If your peak is 4 hours which I'm guessing is a minimum, you are going to save yourself $6 a month.  If it's 2 hours and you are backfeeding, every night/ day mind you cause they get you on the highest one...... you will save $12.... a month.

No one likes to fart about with money saving schemes more that I do. Been running veg oil in my vehicle 15 years, back lawn is half covered with solar panels I have been testing and getting ready to put up, have heated the house with veg oil burners and so it goes BUT...... They do save me money. real money.  This is a cost.  A big one.
If you are happy with that for the price of entertainment/ hobby, that's more than fine but if you are under any illusion it's going to save you money...... it's not. Especially at 4.7 c kwh regardless of the $12 Charge.
If I paid that instead of 30C kwh flat, I woudn't need to screw around with panels.

If you are doing it for blackout protection, as I said, generator and transfer switch and spoil the boy with something nice with the left over money or take the family on a holiday or even a nice weekend away.
If you have more money than you need, then enjoy it because you have well earned it!  :0)

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RJ
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« Reply #32 on: November 10, 2017, 09:09:47 AM »

Thanks for the input Glort, very much appreciated. It sounds like you have certainly gone though it and then some.

Good info on the alternator trial and errors.

I found a good deal on a Cotek SK2500-124 for $600 new.

These are discontinued and the outfit I contacted was looking to be rid of their last one.

Here is the info from inverter supply:

https://www.invertersupply.com/media/data/ST2500.pdf

The unit has a 30a built in xfer switch and is designed to be hard wired in.

It's a well built unit coming in at 26lbs made in Taiwan.

the batteries will cost me ~$400 bucks.

I figure misc battery hardware, cable fuses, etc $200

So for the basic UPS setup $1200 bucks.

Do you have an experience feeding a solar MPPT charger with a power supply, say a 1000w 48v unit which I happen to have handy.

I will keep my eyes open for a few 250 panels to put in the back yard.

As of now I'm looking at this as a simple emergency backup that will run the basics in the house at night (alarm system, fridge, etc) while the generator is off.





« Last Edit: November 10, 2017, 11:58:14 AM by RJ » Logged
RJ
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« Reply #33 on: November 10, 2017, 09:36:51 AM »



Do you have an experience feeding a solar MPPT charger with a power supply, say a 1000w 48v unit which I happen to have handy.



For those wondering it looks like it can at least be done with a morningstar MPPT controller:

http://support.morningstarcorp.com/faq/
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glort
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« Reply #34 on: November 11, 2017, 12:46:01 AM »

Do you have an experience feeding a solar MPPT charger with a power supply, say a 1000w 48v unit which I happen to have handy.


No, never had thought or occasion to do that although I can't see why it would not work as long as the output from the power supply was well rectified.
Output is not going to bounce around and the inverter should be able to find it's sweetspot and settle. If you have something like a forklift battery charger will be fine.

How you thinking of setting it up? Letting it run off AC at night and then the panels supply the power  during the day so the inverter always has an input?
Doing that with an LED light bar ATM for raising seedlings.  Fed by a battery charger and a Solar panel.  At night the charger supplys current. During the day the output from the panel surpasses the chargers output and the current from the charger drops to zero. Morning and afternoon the panel makes part of the current and the charger the other.
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mike90045
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« Reply #35 on: November 11, 2017, 03:43:41 PM »

Do you have an experience feeding a solar MPPT charger with a power supply, say a 1000w 48v unit which I happen to have handy.

Morningstar MPPT works to downconvert a battery.  Other brands are unknown, and I would be cautious, you may need a ballast resistor to make it work.  They generally work because they think they are dealing with a current limited PV panel and rely on raising or lowering the MPPT input voltage to regulate the input power. That may not work with a battery or power supply as a substitute for PV panel
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RJ
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« Reply #36 on: November 12, 2017, 07:09:44 AM »

Thank you Mike. So far morning star is the only one that I have found that will confirm this will work.

I have several JFS1000-48 power supplies.

http://us.tdk-lambda.com/ftp/manuals/jfs1000_man.pdf

Adjustable from 36-56v

Coupled with a Tri-Starr MPPT-60 controller it would work well as a battery charger/PV charge controller.

41 amps at 24v is a little high for a 225ah bank. I can also use this to charge off my inverter generator in a pinch.

C/8 charge rate ~ 30 amps

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mobile_bob
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« Reply #37 on: November 13, 2017, 08:17:07 PM »

fwiw

battery sulfation is a natural process that happens any time a battery is discharged, sulfate will form on the plates

this sulfation will be reversed during the next charging cycle,

the problem for batteries is this, the allowance of the normal soft sulfate to harden.

generally speaking charging to 100% once every week or 10 days, will revert the sulfate before is starts to crystallize and harden. there is much written on this over the last decade or so, in various forums and on various battery manufactures websites.  this is where the "50-80" regime comes from.

charging a battery from 50-80% state of charge allows for a relatively highly effiicient charge, because you can dump a lot of amps into a battery within this window, without excess heating or loss of water.... once you hit 80% and charge up from there you must lower the charge rate and monitor things, to keep temperatures in check, and reduce water usage/loss... the efficiency drops precipitously over 80% the closer you get to full charge.

many systems have successfully used the 50-80 regime, topping off to 100% once every week to 10 days, and then equalized once a month or even longer in some cases.

unless one has a rather large installed capacity of solar/pv panels, or is willing to run long hours with a genset, trying to charge to 100% several times a week over time will be much more costly over the long haul... and it is likely the batteries will not live as long either.

around here, even if i had massive amounts of panels, i can't figure how i could recharge to 100% several times per week, not unless i planned on long generator hours at very low loading?

then again, it has been a very long time since i was part of this debate.

having been in politics for 2.5 years now, i can tell you this...
it has done nothing for my mental capacity!  which makes me wonder why there
are so many idiots in DC!

but i digress

hey i still know how to do that!  Smiley

bob g
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BruceM
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« Reply #38 on: November 15, 2017, 10:44:19 AM »

Bobg's statement of the characteristic inefficiency of lead acid batteries for the last 20% of charge is right on the mark and very well documented by Sandia labs, among others.  (AGM batteries are significantly better efficiency but still less so the last 20% of charge.) By the last 5% of charge you are typically at 45-50% efficiency. This is very important to be aware of if running a generator to charge with.

But it is not an issue for PV charging since this is at a much reduced current.

I would argue that the general statement about the need for an excessive size PV array to accommodate full charging is out of date and may confuse newbies. With PV costs now around $0.33 per watt,  excess capacity for completing bulk charging earlier in the day should be the rule, not the exception.  Check out prices at sunelect.com. Secondly, in most climates, if you have even barely adequate PV to meet typical winter charging needs, and seasonal tilt capability, you already have grossly excessive capacity for the rest of the year.   

Topping off the batteries with a good 3 stage controller takes little PV power away from daytime loads and does not increase water use. Most days, your batteries should be in float by noon.  I am only adding a bit over 1 gallon of water every 2 years and my batteries are fully charged about 360 days a year. 

But you must be smart about your particular batteries and what it takes to extend their service life.  If your bulk charge rate is too high for the battery size and type, you will see excessive water use and plate erosion.  Where a higher charge rate is necessary,  larger capacity batteries at lower DOD or AGMs might serve better.
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RJ
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« Reply #39 on: November 15, 2017, 11:55:21 AM »

Thank you Bob and Bruce.

Bruce is this the site you are referring to?

http://sunelec.com/home/

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BruceM
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« Reply #40 on: November 15, 2017, 03:16:34 PM »

Yes.  I used to shop at Solarblvd.com but they seem to be in a slump for name brand panels, and I don't trust their various store brands having had  problems with them not meeting even 60% of spec.

BobG had a much more detailed explaination on the 50/80 charge scheme on the Lister forum and there he cleared up the issue of using PV. 

For racks,  I like ground mounted, seasonal tilt capable panels unless risk of theft or space forces roof mounting.

A scale drawing of my latest (5) 250/300W panel rack design is attached.  You could cut back on steel sizes if not in a high wind areas like I am.  One man could handle the seasonal change.  1" EMT with smashed flat ends are the braces.
The rest is welded up on site.  This should be roughly $300 in steel.




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RJ
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« Reply #41 on: November 16, 2017, 10:24:15 AM »

Yes.  I used to shop at Solarblvd.com but they seem to be in a slump for name brand panels, and I don't trust their various store brands having had  problems with them not meeting even 60% of spec.

BobG had a much more detailed explaination on the 50/80 charge scheme on the Lister forum and there he cleared up the issue of using PV. 

For racks,  I like ground mounted, seasonal tilt capable panels unless risk of theft or space forces roof mounting.

A scale drawing of my latest (5) 250/300W panel rack design is attached.  You could cut back on steel sizes if not in a high wind areas like I am.  One man could handle the seasonal change.  1" EMT with smashed flat ends are the braces.
The rest is welded up on site.  This should be roughly $300 in steel.



OKay just waned to make sure I had the correct site. I don't see any mono panels listed, but gosh some of those prices are fantastic. He also a great price on the schneider SW4048 at $1400
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