New Solar Panels

[Luv2go]

Originally Posted by CJBROWN

...I guess they also series wire 12v panels for higher voltage when mppt is used.

Yes, this one's claim to fame is it works up to 150V plus the battery voltage. Useful for the 320W or new 345W SunPower panels which run at 55-57V and have VOC on the 70V range. Not many other controllers will do that high voltage.

The SunPower panels are very efficient and do produce their rated power, at least in the winter (I have 30 of the 320W E20's on the S&B, right now they're producing 315 to 327W on this nice, sunny 33 degree New England day).

It would be nice to stick one or two of these on the MH, they are only slightly larger than the 195W panels on it now, but at $295 per panel (not including delivery) plus $400 for the controller it's an expensive option.

[CJBROWN]

Originally Posted by Luv2go

Yes, this one's claim to fame is it works up to 150V plus the battery voltage. Useful for the 320W or new 345W SunPower panels which run at 55-57V and have VOC on the 70V range. Not many other controllers will do that high voltage.

The SunPower panels are very efficient and do produce their rated power, at least in the winter (I have 30 of the 320W E20's on the S&B, right now they're producing 315 to 327W on this nice, sunny 33 degree New England day).

It would be nice to stick one or two of these on the MH, they are only slightly larger than the 195W panels on it now, but at $295 per panel (not including delivery) plus $400 for the controller it's an expensive option.

It's a lot less than some of these so-called RV solar 'experts'. LOL

Wow, that's a lot of panels for the house. I've been looking at solar for the house too and the savings just really isn't there 'till about 10 years out when they're paid for. I don't want a 20 or 25 year PPA, hell I may move on or pass long before that. LOL.

The problem with our rate structure here in CA is that it's tiered and the lowest tier is regulated so it's cheap. But just about everybody goes over, we do by a long shot, so the idea of a solar installation is to knock you down to the lower tiers - they call them 'tier clippers'. The lowest tier is like 13 cents or something, but the top tier is like 27 per kwh, so if we run AC our bill can go to almost $400. We are like the top consumer in our area - pool, reef aquariums, computers, big-screens, LOL.

We were looking at a 16 panel array for about $13K installed. Would knock about $130 off our electric bill (about $250 average) but the payments on the installation would make up the difference. Based on the projected 6% percent rate increases we would start saving some money at about year 5-6, and of course once they are paid off then it's free power, would save us quite a bit. But I have to commit to a 10 or 15 year payment contract to get the savings. I finally decided to wait a bit and see what happens to the industry, electric rates, etc. For all I know I'll learn enough installing my own PV's on my RV to do a DIY install on the house. All of the stuff is pretty much just plug and play now, the installers are making an absolute killing - a rip off as far as I'm concerned. You just need a qualified electrician to connect to the house electrical panel and get the city permits for the installation. I think I could do that.

I thought Handy-Bob's comments on grid-tie solar were interesting. Probably kind of dated by now, but still, our money is probably better spent on conservation efforts - energy efficient appliances, insulation, windows, new furnace, pool pump, lighting, etc. Then see what our consumption is and go from there.

[unyalli]

Originally Posted by CJBROWN

Their least expensive controller is $400, plus $60 for the Wizbang unit, so $460 before you even buy panels.

$286 and $44 so $330

[CJBROWN]

Originally Posted by unyalli

$286 and $44 so $330

Them folks are great aren't they? I got my Iota converter from them and they had the best price I could find on the internet. Good links.


I read thru Vsheets install again and notice he was using pwm controller - I thought the morning star units were mppt.

It's a good write-up.

So I dunno, For $330 I could get a couple of 130-140 panels and spend $75 on a morningstar pwm controller. I'd be almost there. Would be curious to see which one put more amps into the batts, and whether it was worth the difference in cost.

[unyalli]

Originally Posted by CJBROWN

Yeah, I've read that thread. In fact most all of them on the forum and now researching solar forums and google searches.

That demo is still not totally clear for me. Yes, I understand he's getting a bump by switching to a different controller,

Then it is totally clear, this is the point. It's simple.

Originally Posted by CJBROWN

but that doesn't take into account using different wattage panels and differing brands of controllers.

It's not supposed to the video shows the difference in PWM vs MPPT in an apples to apples situation. Not the benefit of one complete system design vs another.

Originally Posted by CJBROWN

He has a side by side with VERY low wattage and amperage.

Exatcly, he is showing even in a low power situation MPPT is better.

Originally Posted by CJBROWN

I understand how mppt works - taking excess voltage from a panel and converting it into extra amperage to feed the charge. That doesn't take into consideration what the bank is able to absorb though.

I'm missing something here. If the load is not pulling the power then none will be produced PWM or MPPT makes no difference.

Originally Posted by CJBROWN

From what I gather you have to use mppt if your panel voltage is over the rated max for the controller, and that the most improvement in performance is when the panel volts are double the charge volts - that way it has something to use to boost more power.

I believe we are at the crux of the problem. Why are you understanding this? Where did you get this from? All you need to charge a battery is a voltage higher than the batteries. With a panel wanting to produce 17.1 volts you have this higher voltage but cripple it with PWM by dragging the panel down to battery voltage. MPPT says go ahead and fly buddy I'll handle the details.

[CJBROWN]

So which controller do you recommend for 300 to 400 watts of panels?

Why are pwm controllers still made/sold if they don't work right?

What I meant was it seems mppt is more efficient when the panel voltage is substantially more than the battery charge voltage. That headroom is fed back through as charge amperage. Or am I just not understanding how this works?

[unyalli]

Originally Posted by CJBROWN

So which controller do you recommend for 300 to 400 watts of panels?

Sir, that's coming at it from the wrong direction. With your current rig you have been doing fine with around 220 amp hours of true deep cycle flooded lead acid battery. In general you want to charge your bank at 10% of its capacity or 22 amps. If your battery bank is all the way down at 50% you want to provide 22 amps of current and let the battery have control of the voltage. As you already know this is bulk charging. You can go over this a bit for a short time so a 30 amp controller would be perfect taking into account your rig using some of it. You want a controller that will provide this and enough panel to feed it. With MPPT you can do this with less panel. Both Morningstar's Tristar MPPT 30 and Midnite's Kid 30 amp units would be great but figure into the cost of the Morningstar the remote meter. Also figure mounting. At 30 amps max you don't have to be right at the battery bank but the morningstar with remote meter would allow this. Back and forth.

I like Morningstar and started this road with a Sunsaver MPPT 15L and two 90 watt panels wired in series. I still have this portable system, it's a great little controller but does not produce enough amps to kick a 220 amp hour bank correctly.

Originally Posted by CJBROWN

Why are pwm controllers still made/sold if they don't work right?

They do work, there just old school and in this case progress is actually a good thing. I'm old school for the most part but also a techie so burning massive amounts of fuel to get into space is asinine. We need anti-gravity.

Originally Posted by CJBROWN

What I meant was it seems mppt is more efficient when the panel voltage is substantially more than the battery charge voltage. That headroom is fed back through as charge amperage. Or am I just not understanding how this works?

For some reason you believe for MPPT to work the difference in voltage from the battery bank to the Solar array has to be huge. Not so sir it takes very little difference in voltage. Further with your batteries down at 50% a PWM controller will drawn down a 17 volt panel into the 12 volt range where it will produce no where near what it's capable of. MPPT will let it run where it likes to and produce maximum power.

We should be sitting on the patio with a beer discussing this.

-Jeff

[CJBROWN]

Excellent Jeff.

So the extra power from a 22v panel vs a 18v is really being wasted with a pwm controller.

What do you think about a Trina or Canadian PV in the 250-300watt range with either of those controllers? Would I see the 20amps I'm looking for?

I was figuring as you describe - using 80-100 amps of battery through the night with a solar array producing about the same amount for an average 5-hour solar day. Does that make sense?

The other thing that's confusing is the amp hour rating of high-voltage panels - seems I can't use those figures anymore for estimating 12v input with a mppt controller.

I would rather wait if I have to spend more to get better equipment than go out and buy stuff that only works marginally. That's just a total waste of $$.

What about grid-tie type panels verses 12 volt's for strength and durability on a RV roof? Any pros and cons? I know I have room for at least one 40x60 panel, not sure I could fit another. But I could put two 100 to 130 watts in series to augment later, right? Connect to the same controller? Or should I keep all the panels the same? Like two banks of 100's in series?

[MRUSA14]

Originally Posted by CJBROWN

Excellent Jeff.

So the extra power from a 22v panel vs a 18v is really being wasted with a pwm controller.

That is exactly what the advantage is of MPPT. MPPT converts the voltage down to wahhat the battary wants, increasing amperage in the process. A PWM controller just throws the excess voltage away.

Why do they still sell PWM? It's much cheaper to produce. They sell for 1/3 to 1/2 the price of an MPPT controller.

[unyalli]

Originally Posted by CJBROWN

What do you think about a Trina or Canadian PV in the 250-300watt range with either of those controllers? Would I see the 20amps I'm looking for?

This is another beauty of MPPT. You can pretty much expect a 1 to 1 ratio of watts in = watts out. I have verified this on my Sunsaver with doc wattson meters. So if we want to hit a 220 AH bank with 22 amps we need around 300 watts at 13.8 volts. With MPPT the math is pretty simple. You can throw this all off with incorrect wire sizing. 300 theoretical watts of panels never produces 300 watts of out put though. A flat panel in winter will be way low on production and tilting it will improve it quite a bit but you still won't see 300 watts out of a 300 watt panel. The only way would be below freezing temperatures and exact tilting which shoots the voltage way up. I played with this in my lab. (My back yard). This is where you would want to be very careful using Bluesky controllers. They don't like high voltage.

Check out this chart. A guy named westyd wrote a program that will poll the sunsaver for all available data. I wrote a little thing that ran his program every two minutes on my Raspberry PI and then sorted it all out and built a spread sheet. It also updated a web page I was running on the PI that I watched realtime. Check out the array voltage (Varray) vs battery voltage (Vbatt) when the MPPT controller starts producing. (T_rts is the temperature at the remote temp sensor on the battery in Fahrenheit.)



Now check out this chart. My two panels in series are supposed to produce 34 volts at max power. Look what happens when you go below the test condition 77 degrees F. You can also see battery temperature compensation at work.

Originally Posted by CJBROWN

I was figuring as you describe - using 80-100 amps of battery through the night with a solar array producing about the same amount for an average 5-hour solar day. Does that make sense?

You have a major part of the battle won. You have a handle on your power usage. This is the hardest thing to get someone to do. I don't remember do you have a Trimetric? Is that how you know your using 80-100 AH a day? If you don't want to run the gen at all you have to put this back plus 3% via solar. If you use 100AH you need to put back 103 AH. 103 divided by 5 hours is 20.6 amps an hour for 5 hours. 20.6 amps at absorb voltage of 13.8 is 284 watts. I believe I have that right. vsheets or one of the others can correct the math if need be. Those guys look to know this stuff pretty darn good I've learned a lot from them.

Originally Posted by CJBROWN

What about grid-tie type panels verses 12 volt's for strength and durability on a RV roof?

Most everyone I've read about is using normal house type panels. I am.

-Jeff

[CJBROWN]

Originally Posted by unyalli

>snip

You have a major part of the battle won. You have a handle on your power usage. This is the hardest thing to get someone to do. I don't remember do you have a Trimetric? Is that how you know your using 80-100 AH a day? If you don't want to run the gen at all you have to put this back plus 3% via solar. If you use 100AH you need to put back 103 AH. 103 divided by 5 hours is 20.6 amps an hour for 5 hours. 20.6 amps at absorb voltage of 13.8 is 284 watts. I believe I have that right. vsheets or one of the others can correct the math if need be. Those guys look to know this stuff pretty darn good I've learned a lot from them.

-Jeff

Good stuff.

I don't have a meter, just been calculating what gets used and what their consumption is. I probably really should think about installing one even before designing a solar array. I know my entertainment system is on a 300w inverter, so if I install a LED TV I figure I'll use about 200w of that or about 16-20 amps per hour of use, the furnace blower is 8a per hour, lighting probably 1 or 2, then to run fridge water-heater and sniffer boards, plus a 150w inverter for an hour or two for a laptop or about 8a per hour. So depending on how cold it is and how much the furnace runs, and how long we would watch TV, consumption is going to be in the 30-100 amps overnight.

Our other consideration that I may have mentioned is that here in southern CA if it's warm at all then the genny runs for AC. I've gone ahead and upgraded the converter to an Iota so any gen run time will charge the batteries pretty quickly.

So I'm guessing that 300 watts of panels or so would be a good place to start. If I find I need more I should build with that in mind. I may also find my 5-year old GC batts are due to be replaced, and I may find I really need to have 4 of them, in which case I'd probly want 400-600 watts of panels. I would also like to do this in stages, upgrading as needed.

Do I understand correctly that mixing panel voltages doesn't work? In other words, if I put a 250-300w grid-tie PV up there and needed more, could I add a couple of 100-130w panels in series? I would think they would be fairly close in panel output voltage. I don't want to get a system in place that I'm stuck with no options to upgrade. I don't think I could fit more than one commercial panel unless I removed my dish receiver (which I've never used. LOL)

You've cleared up a lot of questions I had - thanks!

[unyalli]

Originally Posted by CJBROWN

So I'm guessing that 300 watts of panels or so would be a good place to start. If I find I need more I should build with that in mind. I may also find my 5-year old GC batts are due to be replaced, and I may find I really need to have 4 of them, in which case I'd probly want 400-600 watts of panels.

And 44 amps charge.

Originally Posted by CJBROWN

Do I understand correctly that mixing panel voltages doesn't work? In other words, if I put a 250-300w grid-tie PV up there and needed more, could I add a couple of 100-130w panels in series? I would think they would be fairly close in panel output voltage. I don't want to get a system in place that I'm stuck with no options to upgrade. I don't think I could fit more than one commercial panel unless I removed my dish receiver (which I've never used. LOL)

You've cleared up a lot of questions I had - thanks!

You want to keep the array voltages very close per paralleled array. If you have one array of two 100 watt panels in series that produce a combined Vmp of 34.0 volts and want to parallel in another array it's combined Vmp should be close to this regardless of watts. You could add a set of 140's with a combined 34.5 and when paralleled with the other set it would not run at 34.5 but at 34.0 so you would loose a bit of their power. The lower voltage panels would pull down the higher voltage ones.

[unyalli]

There is another way of determining 24 hour power usage if you can keep your total at once draw below 15 amps.


Kill A Watt P4400 from amazon.

Power your entire RV via this little guy through your shore power cord for 24 hours and get a total accumulated kwh reading. Divide by voltage for amp hours. Your not going to run the air conditioner and should not run the fridge or hot water heater on ac. This would be normal if your going solar.

[CJBROWN]

Originally Posted by unyalli

There is another way of determining 24 hour power usage if you can keep your total at once draw below 15 amps.


Kill A Watt P4400 from amazon.

Power your entire RV via this little guy through your shore power cord for 24 hours and get a total accumulated kwh reading. Divide by voltage for amp hours. Your not going to run the air conditioner and should not run the fridge or hot water heater on ac. This would be normal if your going solar.

Wow, for $20 you could at least get a good estimate of consumption of various appliances and devices. I've heard the published ratings of things are not very accurate. Like furnace rated at 8a but really only draws 6, or even large power inverters that drain a lot on standby.

I would like to replace both TV's with LED flatscreens. I'm pretty sure the front 26 tube going to a 32led is about half the consumption. The bed tv go to a 12v 22-24. I'm not sure what those draw but I don't think it's much, maybe 5a. And replace all the regularly used interior lights with leds. Less consumption = less solar wattage, right?

I just got one of these. Neat little unit, powers the laptop, no fan so it's quiet, $35 shipped. I see this was on VSheet's list as well.