Author Topic: Solar - 24vdc Panel with 12vdc Charge Controller  (Read 418 times)

veggie

  • Keep Calm and Start the Lister !
  • Sr. Member
  • ****
  • Posts: 454
    • View Profile
Re: Solar - 24vdc Panel with 12vdc Charge Controller
« Reply #15 on: August 28, 2019, 02:23:04 AM »
Glort, did you receive your eBay MPPT converters yet?
I'm curious to see how they work.
Mine are still 4 weeks away.
- 6/1 GM90 Listeroid - Delco 33si Alternator
- Changfa R175 - Lease/Neville Alternator
- Kubota Z482 - 4kw
- JiangDong R165 Air cooled - 2 kw

glort

  • Hero Member
  • *****
  • Posts: 2977
    • View Profile
Re: Solar - 24vdc Panel with 12vdc Charge Controller
« Reply #16 on: August 28, 2019, 04:19:15 AM »

Yes mate, I have got a whole bunch of the things. I forgot how many different ones I ordered!
The last lot arrived yesterday but I haven't tried any yet.
I might go try something this afternoon now I am finished Mining in the Kitchen floor.

I hooked up 4 175W panels directly to a 3600W element and put that in a 25L tank in the fridge I am using for raising seedlings.  I boiled the water! :embarassed: Certainly the day have been sunny but I didn't even calculate and grossly over guestimated the power required.

Pulled it back to 2 panels and seems plenty hot.  I read a guy on YT going on about his controllers and being able to make 6 gallons of hot water which is less than 25L .  I wonder why the hell you wouldn't just throw a couple more Panels at it and be done with it? With 4 panels maybe paralleled/ series connected and a Controller, I reckon 125L might be more feasable.  I have been playing with 100L + and sort of missed how relatively easy a small amount like 25L would be to (over) heat but I think it's pretty dam useless for domestic purposes.
There is a 30L heater at my holiday house and it's a one shower job at best. Being on mains it takes about 45 Min to heat back up so isn't unworkable for that use.  A warm wash here at home would probably kill it though.

First thing I want to do with the controllers is see how much better I can make the output of the panels by bringing them back to power point which I'll do manually. Then I'll add a cap bank and see how that goes. the last thing will be to make the automatic PWM switching. I have the boards I'm going to plat with that as well which also arrived yesterday.

I like getting this stuff in the mail.  It's like Christmas only better because you get stuff you actually want rather than having to smile, say " Oh wow" and at the same time be thinking " What the F.. am I going to do with this shit?"

Today was a GOOD present. I bought myself this head light thing after getting one at bunnings the other day and finding out how dam helpful they are.
It has 3 Lights which can be single, double or all 3 and came with 18650 Batteries, a charger, cable and a Mounting which I think is for bike handlebars.
I unpacked it, put the batteries in, put it on, turned it on through the various modes  and then sat back down and ordered 3 More of the things.
For $10, best buy I think I have made in a while. 

More presents to arrive next week Now!   :laugh:

glort

  • Hero Member
  • *****
  • Posts: 2977
    • View Profile
Re: Solar - 24vdc Panel with 12vdc Charge Controller
« Reply #17 on: August 29, 2019, 06:48:05 AM »

being a man of my word, ( on rare occasions) I went out and tested the PWM controller on the panels and heater element.

Unfortunately yesterday was bright and sunny and when I went out it just so happened that the voltage I was getting off the 3 panels I had hooked up matched the element impedance  within .9 of an Ohm.  As such the PWM could not make any improvement on a direct connection.
Today is the opposite and so cloudy that the panels aren't making enough to even get on their  Curve within anything I can adjust for or more over, accurately measure.

I haven't used the cap bank yet, no doubt today it would make a difference although probably a slight one due to the fact the PWM cycles would I think be firing way too fast. Something with a much slower pulse like an arduino driving the pulses would no doubt be much better for this low an output.

I'll try again tomorrow but the nut shell is having an array of panels and dividing the voltage between them to stay on the power point of the panels to give the most efficiency.


glort

  • Hero Member
  • *****
  • Posts: 2977
    • View Profile
Re: Solar - 24vdc Panel with 12vdc Charge Controller
« Reply #18 on: September 05, 2019, 01:43:13 AM »

I have Given the PWM controller a few more tests and not come up with anything real exciting.
It seems the benifit when direct connected even with matching the sweet spot of the panels is not very significant at this level. I have tried 2 and 3 panel setups with the 3600W element but it's a real fine line for the peak efficiency at  this low output. I doubt at the nd of the day there would be much difference in and reasonable amount of water with and without the controller.
If it was ramped up to a total of KW instead of hundreds of watts, then I expect the difference would be more but that's beyond the scope of the controllers available without modification.

I haven't tried using a cap bank and am hoping that makes the difference.  I'll try to get a DC watt meter because working out every equation with volts Vs amps is not practical. If I had a watt meter and can just see a higher number I'll know where I'm at. I thought... I'm sure I have a DC wattmeter somewhere on something but I can't think what it was. Might have been my solar battery inverter setup. I'll go dig it out and look.

One thing is pretty clear though, if you get lucky with the panels and element you are using you are going to be pretty close in the ball park to start with.

Seems I might have hit the magic numbers at the one time I prefer not to. Next I'll try the caps and then changing the panels for something else.
Can't be annoyingly lucky twice!

veggie

  • Keep Calm and Start the Lister !
  • Sr. Member
  • ****
  • Posts: 454
    • View Profile
Re: Solar - 24vdc Panel with 12vdc Charge Controller
« Reply #19 on: September 05, 2019, 02:46:26 PM »
Thanks Glort,
I assume you are talking about the module shown in the picture below...
From what you have seen, will it work as a crude charge controller with my 24-34vdc panels charging a small 12vdc battery?
I have a 50W (24vdc) panel and wish to solar charge a small gel-cell battery which powers a micro-controller at a remote site.

Mine have still not arrived  :-[
« Last Edit: September 05, 2019, 07:30:46 PM by veggie »
- 6/1 GM90 Listeroid - Delco 33si Alternator
- Changfa R175 - Lease/Neville Alternator
- Kubota Z482 - 4kw
- JiangDong R165 Air cooled - 2 kw

glort

  • Hero Member
  • *****
  • Posts: 2977
    • View Profile
Re: Solar - 24vdc Panel with 12vdc Charge Controller
« Reply #20 on: September 05, 2019, 11:39:13 PM »

Hi Veg,

The one you showed was the one I DIDN'T order!   :0)
For what I want to do it's not suitable as it's MPPT rather than PWM and I can't externally drive a Mosfet with it.

For what you are describing you want to do with it however, I'd say it's perfect.  It has an Inductor coil ( which was why it was no good for my purposes) so will allow the Voltage Mismatch of the panel and the Battery.  I might order a couple of them myself actually, I found a good small Panel I was given a while back and I  thought about putting it up the back in the machinery shed and putting it on the  tractor as the regulator is not working on that and I am just recharging the battery every so often which isn't great for it.
  In any case sometimes it's a couple of weeks before I use the thing so having a charger on it would be much better.

I have a STACK of different controllers sitting on my desk in front of me to try out, modify and build into circuits for this idea.
The controller I'm playing with atm is a 90V, 15A capacity unit which was the highest pre made board I could find.  I was thinking I could upset the impedance match I have with the panels and the element by adding another set of panels in parallel with the first ones.
This will halve the impedance of the panels and -may- give me more power as well depending on the setup.
Again I think to make that work I'm going to have to bring in the capacitor bank  to store the panel energy between pulses.

I'm also beginning to wonder if I have gone the wrong way all together and for real low outputs it would be better in the long run just to buy a low Voltage element and be done with it?  Being a tight arse and being able to get AC elements anywhere for Nix, that was the route I preferred to take.
One the 3rd or 5th hand, what ever I am up to, the low voltage elements I have seen are all pretty low output, 6 or 900W.
I was pulling1800W out of a bunch of panels on another array yesterday on a 3600W element hooked to 3.75 Kw of panels in series.
Might sound bit of an inefficiency but given the season here and the fact the array is way off ideal tilt, I thought it was pretty good being they are never going to produce perfect efficiency to start with. I might if I get a chance test what I get with the array direct coupled and what I get when Hooked to the GTI.  At some times it should be very similar, at others the GTI will be miles more efficient as that's what it's there for in the first place.

Certainly 1800W is going to heat a decent amount of water up a lot faster than 900.

I have another idea yesterday for matching the impedance of the panels. 
At different times of the day the panel output and impedance ( resistance ) will vary.  If multiple elements were used and switched in and out, the impedance could be varied higher or lower and a better match for the panels at that time would be created.
I'm thinking this would be best done by voltage monitoring and would give a similar effect to the PWM of the panel voltage to keep them in the sweet spot which is what we are trying to do. It would be far more staged but none the less give a decent efficency improvement.
I could possibly switch the panel arrays from Series to parallel and Daisy chain the elements also which could give 8 stages pretty easy I think.

Most water heaters will only take a max of 2 elements here but if a custom external element pack was built with say 2 more elements and a solar Circulation pump used, then this could be incorporated fairly easily. I do remember seeing something similar on the net some years back where a guy had something like 20  500W cartridge heaters in a pipe and was switching them with a load of SSR's .  Rather expensive setup but this was probably what he was doing. I do remember him being questioned as to why such a big heater setup and he had a massive amount of panels as well and the reply was he was running a guest house / small holiday resort and had a large hot water demand.
If I can work out how to stage the panels, then a twin water heater element should give a minimum of 4 stages and If I had 4 arrays, might be possible to again have 8 stages of resistance which would allow pretty tight matching.  I'll have to do the mental and practical arithmetic on this  but it should just be swtching.  The control part would be the trick as always.

I did get I think it was a thermostat board with staged outputs I was going to look at converting  to a voltage input signal which is what a thermo couple would work on anyway  but given the voltages used, It will take some real accurate setup to make it work.

All I need to test and work through all this is a completely parallel life with nothing else to do.   :embarassed:

veggie

  • Keep Calm and Start the Lister !
  • Sr. Member
  • ****
  • Posts: 454
    • View Profile
Re: Solar - 24vdc Panel with 12vdc Charge Controller
« Reply #21 on: September 05, 2019, 11:52:26 PM »

Thanks Glort,

I might order a couple of them myself actually, I found a good small Panel I was given a while back and I  thought about putting it up the back in the machinery shed and putting it on the  tractor as the regulator is not working on that and I am just recharging the battery every so often which isn't great for it.
  In any case sometimes it's a couple of weeks before I use the thing so having a charger on it would be much better.


That's the exact reason I bought two.
My tractor can sit for months before I use it. I want to use my second 50 watt panel to keep the battery charged.
However, I'm not sure that this little controller is smart enough to scale back when the battery is full.
Will have it investigate.
- 6/1 GM90 Listeroid - Delco 33si Alternator
- Changfa R175 - Lease/Neville Alternator
- Kubota Z482 - 4kw
- JiangDong R165 Air cooled - 2 kw

glort

  • Hero Member
  • *****
  • Posts: 2977
    • View Profile
Re: Solar - 24vdc Panel with 12vdc Charge Controller
« Reply #22 on: September 06, 2019, 02:04:31 AM »

Being MPPT and the tests I looked up on the net say it is a true MPPT  and a good one at that, I don't think you need to have any concerns at all. I'm sure it will do exactly what you want.

From what I can see, you may have to set the thing up initially.  The instructions say to charge the battery and keep an eye on the voltage and ajust the trimpots to give the cutoff voltage you want.  Seems to me nearly everyone has their preferred end/ cutoff voltage  so you can set the controller to give you what ever you want.

I'm thinking it's likley to be set up for 12V out the box but whether you want 14.5 or 14.8 or something else is up to you. I don't think there is any question it's smart enough to know the end voltage, from what I saw the thing does a very good job in all aspects.
The thing will be just to initially check it and ajust the settings to what you like.

In my experience those little trimmers either take 5 turns to adjust something a volt or they adjust 10V if you breathe on them.  :0)
You should only have to do an initial setup and then they will be fine. This is the same as some better solar battery controllers I have with an LCD readout. They  all have settings for low voltage cutoff and end charge/ Float voltage.

From what I have seen, you have bought the best boards available for the job and should work very well for you.  :0)

veggie

  • Keep Calm and Start the Lister !
  • Sr. Member
  • ****
  • Posts: 454
    • View Profile
Re: Solar - 24vdc Panel with 12vdc Charge Controller
« Reply #23 on: September 06, 2019, 02:54:02 PM »
Well ... if that's the case then I would say that a price of $10 for these little units is the best bargain out there.
An adjustable MPPT charge controller for small batteries (or maintaining a vehicle battery) for this price is a great deal.
Having said that, I am mindful of where it is made. I will report back once my charging system is active.
- 6/1 GM90 Listeroid - Delco 33si Alternator
- Changfa R175 - Lease/Neville Alternator
- Kubota Z482 - 4kw
- JiangDong R165 Air cooled - 2 kw

glort

  • Hero Member
  • *****
  • Posts: 2977
    • View Profile
Re: Solar - 24vdc Panel with 12vdc Charge Controller
« Reply #24 on: September 06, 2019, 04:41:27 PM »

Like I said, everything I found on them, and I did do a reasonable amount of homework as usual, said they were really good.
I don't believe in writing everything Chinese off either. I think there is a lot of bias and out of date thinking there.
Certainly there is some real crap but then again, I can point to some real crap coming from anywhere in some product or another and much of it isn't too cheap either.

In my game, a LOT of Japanese and european gear has been almost completely given up on for Chinese stuff.  Initially they ripped off the OEM  products as they do and they did them very well and very cheap. Now they have just picked up the ball and run so far and so hard with it, people look at the OEM stuff as hoplessly under featured and severely over priced.

 I remember buying some of the Chinese gear when it first came out. I wanted it for what I thought was akin to a Suicide mission. I got lambasted on forums as being  a cheap arse, which I certainly am, but the stupid and other things turned out to be others not me when everyone soon woke up the stuff was in many ways better than the OEM and so cheap it was virtually disposable... except that no one ever seemed to break the things.
My Suicide gear came though without a proverbial scratch even though exactly what I thought would happen did.  Many others including the OEM flag wavers even admitted they would not expect the brand name gear to survive what I showed the Chinese gear had.  Still have the stuff today and use it occasional although it's way under featured compared to what is now available... for literally a 5th of the less featured OEM offerings.

My experience and that of other people I know with a considerable amount of Chinese machinery, easily over 60 different items, has been fantastic.
I only know of 3 failures and they were all operator error that has caused thousands of brand names to fail. Engines just don't like being run without oil  and chainsaws have this aversion to running again when you drop them 30Ft  out the basket of your boom lift. Apparently the Chinese gear is a bit weak when being run over by 26ton excavators as well.   :0)

I have several Chinese Solar battery charge controllers ( Only have Chinese controllers ) and can't fault them either.  Yeah, some are as simple, cheap and basic as they come but they do work as advertised.  My better ones are bloody brilliant. There are many MPPT controllers and some of the higher end Chinese controllers are now well preferred by the off gridders than anything else. Hundreds of YT vids on the different units.

The other thing of course is how many brand names people swear by are made in China now.
There isn't much made anywhere else.
A guy I am friendly with imports a LOT of stuff from China and goes there 4 times a year.  His opinion is you get what you pay for with them. If you are after lowest price, that's what you get with lowest quality as a bonus.  If you want quality and tell them that, that's exactly what you get for surprisingly little extra.  He laughs and tells me how people he sees there asking about making replica parts will give him a price to make the same thing, a lower price to make cheapest and then another price where they will point out design flaws and failure points and tell him they can give him a product that will eliminate all that for a buck or 2 more like it's 100 bux on a $50 part. He said the only problem with getting the good quality is you never sell them again because they outlast what they are put on.

I think you are going to be pleasantly Surprised with these things mate.