Solar Panel Q&A's

[Guest]

No A but have a Q.

 

If you get a Amorphous panel they output at 60W's odd where Mono or Multi-Crystalline output at 22W's odd.

 

So am I right in thinking a Amorphous panel could be used to trickle up a 24V battery bank?

 

No, knot the eco dwelling, a big ketch this time.

[wheels 543]

Were you supposed to say 60W and 22W as in Watts KM? or was that supposed to be V as in Volts?

Watts is the sum of Voltage x Current.

The problem with a solar cell is that there is no actual Voltage limit to what it can produce. The more Solar Energy falling on the Panel, the higher the voltage becomes. It just happens that they tend to top out at a certain Volatage area. The Power rating is determioned by what the combination of the Volatge and the Current the panel can supply equates to.

In an easy answer to your question, the more the output rises above 24V, the more the battery will charge. However, the charge may be insignifant and of no help to maintaning the battery. Not untill the Voltage rises to about 27.6 Volts will the battery be actually charging to some helpful point. Even then, it will never reach full charge. And the Current has to also be of an amount that causes the battery to charge. Just as it would be usless having a Volatge of 1V and 1000A of current available, it would be equaly usless to have a Voltage of 28V and only 0.001A or 1 mA. Nothing would actually happen apart from cooking the power supply. In fact the resting Voltage of the flat battery would not change, so the power supply would be pulled doen to its voltage. So what you actually need, is a combination of Voltage and Current, which once again is Power or Watts.

OK hopefully you haven't glazed over and got lost.

The other extreme is that you can not supply a voltage of 28V and 1000A of current safely either. The power would be so high it would heat up the battery to boiling point, warp the internal plates and damage it. In a more realistic case, depending on battery capacity, you could have 28V and say 2A of current and still boil the battery. Called over charging. There is a point where the current is ruffly matched to Battery capacity and the Solar panel can be left connceted all the time because it will never over charge the battery. But it is determined by battery capacity. Oh and partly by what kind of battery technology the battery is as well. Like Lead Acid, or AGM, or NiCad, and so on.

Does that make sense and help?

[wheels 543]

And to add further, depending on Sun energy, a Panel can put out a high voltage, but in the shade or as the Sun sets, the Volatge can drop dramatically fast. The flash solar regulators are called MMP chargers. There are other flash designs to. What they do is to take the current and do some trickery and increase the voltage with it, so as even though the Voltage drops away, the charging power int he bank can be maintained for much longer. Not all regulators are equal. It pays to spend a bit on a decent charge controller, or all that money you spent of panels is completely wasted dues to most of it never getting to the battery.

[Absolution 7]

What Wheels said.... here's what you need:

 

http://www.trademe.co.nz/Trade-Me-Motor ... 846169.htm

[wheels 543]

Except MMP. I was just about off to sleep last night when I suddenly thought, shoot, I wrote the wrong thing. Too lazy to get up and change it and half expected someone to have done so.

PWM is one of the technical terms used, although you may see it called other things. Pulse Width Modulation. So they have a charge "power" available to the battery that is derived from the Curent and Voltage, and the width or Time that that charge period is supplied is altered and not the amplitude. There are more complex methods of that same thing and can be called something different to make the charger look more "important", but in a nutshell, they are all similar. Solar panel charge controllers are probably one of the most complex of charge controllers because they have to cope with a dramatic and comlex variation of input Voltage and Current.

[Guest]

Here's another question. Is it feasible to hook up the solar panel to the ciggy lighter in the cockpit, leave the batteries on and leave the switch on the panel on? Will that charge?

[Guest]

Damn, Yes meant Volts knot watts. Been tinkering again and got all twisted up by the looks.

 

Found some nice 40W Amorphous panels so was going to drop one on the ketch to keep her alive rather than burning diesel now and again. Got so tangled up with my 12V's I wanted to check my 24V thinking was on track. She's all 24V which then gets fiddled to 12 and 240.

 

Those controllers are great, got one on the Reptile and I'm sure it lets more juice in than the old full her up and shut off one.

 

I'd always use a controller partially as all panels and gear are rated at the world standard of 1000 sunbugs per square metre hitting panels where NZ actually runs an average closer to 1250 sunbugs, or something a bit more techo than that but with those numbers. So gear in NZ is working with 25% more Who-Ha hence I reckon it needs controlling better. Didn't get too techo there for you did I?

 

Building a sun tracker for the eco dwelling panel/s at the moment. V1 was good but gliched then reset itself East at around light speed twisting the head just about clean off V2 has bigger metal and smaller motor I reckon if I get that working well it'll give 30-40% more input a day, a huge gain. I want to try and run off a 85W but have left room to go up to 225W's even if I reckon a sun tracking 140 would be overkill. Just being a tad careful in case the council turn up, they have lots of, predictably stupid, rules on panels including special fees if you want to install one.... surprise knot, the counter productive dickheads.

 

Thanks Gents.

 

Yes it should BM but unless it's 5W or under the wisdom I've tapped suggests it should have a controller. I had a 5W un-controlled trickling mine boat up and it worked sweet. It put a little back but if the batteries had been hammered and you wanted to do it again the next weekend a 5W panel didn't cut the mustard, it needed a pump up by more horsepower.

 

One thing to think about with that though BM is that it means your boat is powered up full time. Many don't like that idea, me being one. We've run into more than a few occasions fully powered boats leaking the odd volts or 2 causing grief to them and neighbours. Also a lot of times we've been on playing with anchoring gear only to bump the windlass switches and the bastards are live. I know one dude who lost a finger to that, come close myself once or twice.

 

I put a dedicated plug in for my panels and thru a controller. Plug in cockpit and wire, knot large, direct to controller next to the battery so I can totally kill the boats power yet get nice battery input. Easy peasy and the bonus is these MMP controllers, I only have a small 5 amp one cheap as chips, do get more juice into the battery even with a tiny 5W panel. At best I'd expect 0.4amps on a full on summers day. Anything over 5W uncontrolled in Summer could easily start to cause damage I would expect.

 

I have a 40W I use when cruising which just plugs in as you describe as well. The 40Wer on a average day supplies our entire needs unless daddy goes hard out with the stereo. But that's changing to a MP3 drive rather than CD version so a huge power saving, spinning that CD sucks all the juice. My masthead Tri-colour light consumes more power than all the other lights combined.

 

I must say I am enjoying the playing with this stuff. Learning too much and now verging on being one of the most dangerous creatures known to man, The Enthusiastic Amateur

[wheels 543]

The size of panel connected is related to how big the battery bank is. In some cases 5W maybe too much, in others, no where near enough. But if the panel is not big enough, you could run into a problem of the battery actually giving a voltage reading that suggests it is OK and have absolutley nothing in it. Or the battery could be drained and then the panel does not have enough grunt to get it back up out of dead flat again.

Very simple regulation is not expensive and will stop the accidental over charge of a battery. Which can save you from two things. The battery being boiled and an electronics that maybe switched on, from being supplied too much voltage. Especially when the battery boils dry and goes OC, then a 12V panel on a Sunny day could go well into the 20's with voltage and fry some instruments. So any controller is better than nothing, but those tricky controllers just make things so much more safer and extract more juice from those little light bugs than you normally could get.

Here is a thought. Assuming you are on a swing moring, If you have a bilge pump on board, a decent panel may just keep the battery charged enough to keep up through the night and replenished enough during the day to keep up the next night. It just may stop keep your pride and joy from sinking.

[grant 40]

the rough calculation i was told for 'self regulating' i.e panel direct to the battery, was battery capacity in amphr needs to be 2 & 1/2 times the solar panel size in watts.

although that was in a use where there was regular draw off from the battery, and generally flooded batteries.

 

also..the latest greatest regulators that wheels was referring to are Multi Power Point Tracking (MPPT), these are the ones that play with volts and amps to keep charging at the most efficient point as long as possible. They also allow you to do weird things like have you solar panels at a high er voltage than the batteries, eg if you had three 12 volt panels but a 24 volt battery bank you tie the panels together to get 36 volts and the regulator will adjust that to charge the 24 volt battery. Why? you might ask? higher voltage means less losses over distance (panels to regulator) and lower current, meaning the cables don't need to be as large.

 

PMW (pulse width modulation) are the previous 'latest best thing' and among the good regulators, probably the most common ones available the moment.

[Guest]

MPPT knot MMP is what I meant. Bloody hell, rampant dyslexia lately.

 

Didn't know that panel size V's battery size thing, that's interesting. I've just been running a simple 'over 5 go controller' programme.

 

With my 5W panel I've seen 26-27Volts peak on a hell sun day. After I fitted to MPPT controller, to take the 40w but now does both, I saw around 13 coming out of the panel one late arvo but 14.4 out of the controller. Some flash smoke and mirrors going on in there for sure. I did check to see if it was a fault but apparently that's what they do, it's all about even power into the batteries.

 

I'm sure I get more out of the 5 with the controller than without it and I don't have to worry about killing batteries. We have 1 x 120ahr deep cycle aboard, the claytons Deep C knot a true Deep C I suspect.

[wheels 543]

MPPT, yeah that's the one. We're all getting confused.

 

The fact that the 27V is seen, is because there is no load KM. Think of it like this.

You are driving down the road in a 100Hp car in top gear. Foot is hard down on the pedal. Now you do a Dukes of hazard and leap over a missing bridge clean across a river. You keep your foot down on the accelerator pedal. As the tyres come clear of the road, your engine will rev like crazy. Suddenly no load. The potential of power has not changed. The engine is still 100Hp. You hit the road on the other side and the engine imediately drops back to the same RPM again. The load has returned and the tyres are now doing their job at propelling you down the road.

The 27V you see is with no load. And thus no load, no current is being drawn. Back to the power or Watts thing, the 60W panel is a function of Voltage AND Current. So our 60W would, @ 12V produce 5A.

12.5V = 4.8

13.8V = 4.35

So as you see that Voltage and Amperage is a constantly moving target and they change in respect of one another and in respect with the load.

Slightly aside, but maybe someone is interested, the Load which in this case is measured in Ohms, also changes as the battery charge changes. As the charge rises on the battery, the resistance decreases or....the load is decreasing.

[Guest]

Yeah, the 27V was straight off the end of the panel wires and it was a serious sunny day. 21-22V was more the common number seen.

 

I was thinking about using a couple of the 40W Amorphous panels for the Eco dwelling but a good monocrystalline panel is far more efficient or so they say. 8% verses 15% sort of thing. And a good 85W mono costs less then 2 x 40W Amorphous.

[wheels 543]

You know how they say that every so many years (can't remember the exact number) MicroP's double in speed. Well the same can be said for Solar panels. Panels are increasing in power and decreasing in price rapidly. We can measure the change in months, as in there is a marked improvement annually.

There are about 4 different base technologies of semiconductor materials in use today and about 3 to 4 variations in each, making a good dozen or more types of panels. And as of 2010, the most efficient are now in the range of + 40% efficient. Panels down in the 5 to 12% are old old old technology. Both Amorphous and Crystaline are around 20% efficient as of this year. The biggy is trying to find someone selling them.

As everything, there are good an bad panels. But age tends to be the big divider, where as price and power don't tend to be, like in most other things on the market. The reason for this is that power and price is the driving force behind the development. Everyone is trying to and of course therefore the selling point is, more power from less space and thus cheaper. Surprisingly, the Chinese Gvt are putting huge amounts of money into panel development because they need to find ways to generate power for a very fast growing nation. So Chinese panels may not neccesarily be nasty to go with the cheap.

Now also, like all things, different technologies work differently. So one panel type does not mena it is best over a complete range of use. Some panels can not handle a very small shadow. A shadow from just a line can drop the panel output to nothing on some. Others are not good with heat. The efficiency drops dramaticaly as the temp rises. Some have to be directly facing the Sun. There is a new generation panel called 3D that does not have to track the sun. The Cells are bult like little towers and all stand like a small broad city and so the Sun falls directly on a cell surface at any angle.

Of course there are now the panels that work in a wider spectrum than just visible light. UV and IR is now being used and the cool thing about UV is that it can be more powerful on a cloudy day than bright sun. So it will generate power all Day now matter what the cloud cover.

[Guest]

I found some in Germany that are basically printed onto cloth. Very high efficiency but roughly 27 gazillion dollars a Watt. Very new technology and something to do with that solar aircraft that's been playing around lately.

 

From my sussing and for the average dude, most of the Chinese made are pretty good. Maybe knot quite up there with BP and those dudes but bloody close. Generally the Chinese are better Watts for the buck but you have to watch out for the usual Chinese short cuts. The 2 biggies being the lamination and black box as in is are they water proof?, most are but some aren't. The other is the frame and/or mountings, again some are flimsy and won't last that long especially if subject to harsh winds.

 

I like Suntech myself. Chinese made but top end chinese. Hunt around and you can pick up a 85W for 400 notes, 2 years ago that would have been 800. One of those Sceta controllers Fineline mentions above above and you're all go. That is what is powering the Eco dwelling or will be when I sort the tracker out. That should give D1 more than enough juice even after a few days of crap mid winter. In summer it'll be OVERKILL so I might divert some for cruise lighting in the man cave, even though that has a mains connected power cable the size of a sewer pipe. A be nice the the environment in one hand and hammer that crap out of it with the other programme

 

I reckon I could solar/wind combo power the main house for around 10K, say 12 after some tweaking to fittings. With a average power bill of $200 it'll pay for itself in 5 years, probably a lot less with power going up at what seems like 5% a month, and then should still have another 10-15 years of economic life left. Oh, I wonder if I'd get carbon credits if I did?

 

In the US if I did solar the main house the Govt would pay 1/2 at the moment. They should do that here and take the load of what seems to be a very pushed grid.

 

I'm gearing up for the next construction using Nano Dots now. Solar is sooooo old school

[wheels 543]

Suntech is good stuff. They are one of or are the most efficient in that tyope at the mo. 22% as of this year. Interestingly the US has just imposed huge Tarrifs on Chinese panels. Suntech have done some major installs in the US and one was a large Military install. Obviously some yank with some political clout didn;t liek the fact he missed out on the Tender process.

[Guest]

I have a 10 watt flexible panel. Do I need to run it through a regulator?

[wheels 543]

What size is the battery??

[Guest]

Not sure, there are 3 batteries, 2 house, 1 starter. Normal size I guess, nothing huge.

[wheels 543]

Yeah the 10W should be fine.

It is the bank capacity that determins what the panel size you can get away with is. If you had one little batery, it is possible it could get overcharged.

[Guest]

I use of of those number plate sized units from Repco, sitting on a bunk where the afternoon sun hits it to keep my start battery up.

It is just enough and the battery is still good after 5 years of abuse.