Sun 90 solar panels

BB. · February 2009

Re: Sun 90 solar panels

What is the Vmp of the other panels?

You can print out the Sunpower Report and relabel with the 90 watt panel voltage/current (the curve itself will probably not change profile between the 200 watt panel and the 90 watt panel).

If the "red" curve is a "standard" panel (same Vmp as the rest of your parallel string), you can plot the Vmp and I at Vmp of the higher voltage panel and see what the current is... Looks like a 20-30% reduction in available current.

That probably accounts for the demonstrated 41% reduction in power in the tested 200 watt panels (IV transition is quite degraded wrt the "good" panel).

Since you are using a MPPT controller on this string (?), the reduction in power (watts) is probably the governing equation.

If you were doing it in PWM, as long as Vmp (impaired) is still above the Vbatt+Vcontroller+Vwiredrop voltage--then only the reduction in current would be the governing process.

Does this make any sense?

-Bill

icarus · February 2009

Re: Sun 90 solar panels

If memory serves, (I'm still away for a couple more weeks,,, enjoying spring before returning to winter!) my current string has a Vmp of ~17.4

I suppose in pinch I could wire the one panel through a separate PWM controller, but somehow that seems to be a bit much.

I'll have to see what happens,,, Some times the devil is in the details aint it!

Tony

Horsefly76 · February 2009

Re: Sun 90 solar panels

Setting the panels/system up 12 volt parallel is not a problem for me.

I just may give the sun 90's a run. The positive ground is not an issue, I can work with that. My current inverter and 160amp alternator do not use case for ground but a separate post.

I was told that if I parallel more than 3 batteries in a 12V system and push more than 100 amps, that I "Didn't know what I was doing and needed to pay some one for schooling before I kill myself"

As a bit of background I spent 12 years as an aircraft mechanic working on everything from 2 seat Cessna's to 747-400's before I was forced in to the rental industry by layoff's

Funny that the systems I deal with on a daily basis consist of between 4 to 8 100 to 315 amp hr deep cycle batteries in series or parallel circuits. Most with "no load" operating current flows of 80 to 200 amps.

My seven 12 volt 100 amp hr AGM'S have all been tied together working as one 700 amp hr battery for (knock on wood:roll:) a year and a half with no problem's.

What you guys think? Am I off my rocker yet:p

Thanks! for all the reply's, thoughts, information and ideas.

This forum looks like it has a good foundation of knowledgeable helpful people!

Aaron.

BB. · February 2009

Re: Sun 90 solar panels

Aaron,

We are all pretty practical people here... The 100 amp maximum recommendation is just that... If you have the larger battery(ies) and heavy cable, and proper wiring / fusing / breaker practices--you will do just fine.

And we don't expect people to toss all of their 12 volt equipment just satisfy a "rule of thumb".

But, if you are staring with a new system with fairly large loads (4 kW or so)--going to a 48 volt battery bank makes sense. There is less copper, the fuses/breakers are cheaper (in smaller sizes), the 48 volt inverters don't cost any more, and if you are using solar charge controllers on PV Panels--they are rated by maximum current--so a 48 volt configured battery bank + 80amp controller will handle near (60v*80a=) 4,800 watts of solar panels--whereas an identical 12 volt setup will handle (15v*80a=) 1,200 watts of PV Panels maximum (would require 4x as many charge controllers to manage a 4,800 watt PV array).

(boy, that was an ugly paragraph

).

-Bill

Horsefly76 · February 2009

Re: Sun 90 solar panels

Hi Bill

The most I am planing on for now is about 1200 watts DC or 100 amps draw at the very most.

During the day (leaving the grid for heavy stuff like heat / A/C, fridge, water heater) my wife and kids use between 200-450 watts ac running lights tv's computers and a portable evap cooler (200 watt draw on high) that we use in the living room during the peak electric rates from noon to six pm.

The cooler helps a lot on a hot dry 100+ deg day to take some load off the central a/c, and put some humidity in the air.

As time/money allows I will build the system to do more.

Aaron.

mike95490 · February 2009

Re: Sun 90 solar panels

icarus wrote: »

Mike,

I'm not sure what you are saying.

Are you suggesting the only time it would matter to me is on a hot day, when my batteries are nearly full?

Tony

You will have to check the specs for a hot day, add 30F for the deep blue panel roasting in the sun, and see what you calculated Max Voltage is. Subtract 2V for controller losses, and see if you have enough voltage to charge with.

System2 · February 2009

Re: Sun 90 solar panels

Horsefly76 wrote: »

Hi Bill

The most I am planing on for now is about 1200 watts DC or 100 amps draw at the very most.

During the day (leaving the grid for heavy stuff like heat / A/C, fridge, water heater) my wife and kids use between 200-450 watts ac running lights tv's computers and a portable evap cooler (200 watt draw on high) that we use in the living room during the peak electric rates from noon to six pm.

The cooler helps a lot on a hot dry 100+ deg day to take some load off the central a/c, and put some humidity in the air.

As time/money allows I will build the system to do more.

Aaron.

Aren't you putting a lot of extra work on that a/c compressor running a evap at the same time?

Horsefly76 · March 2009

Re: Sun 90 solar panels

A/C is shut off when the Evap is running. Evap runs off sign wave inverter/ battery bank.

We run the evap in the afternoon when we are charged the most for electricity.

On average we get a 20 deg temp drop from inlet to outlet and it adds some much needed humidity to the air.

System2 · March 2009

Re: Sun 90 solar panels

Horsefly76 wrote: »

A/C is shut off when the Evap is running. Evap runs off sign wave inverter/ battery bank.

We run the evap in the afternoon when we are charged the most for electricity.

On average we get a 20 deg temp drop from inlet to outlet and it adds some much needed humidity to the air.

I do understand that you were not running them at the same time. But I would think you are loosing any energy and cost savings with the extra time the A/C has to run each day to remove all that humidity from the air. A lot of extra work on that compressor, no???

I live in AZ and use the evap as deep into the summer as possible. When the dew point hits 50%, forget about it. So I do know about extremely dry air.

My point is maybe you would be using less energy and spending less if you were to set the A/C at 80 degrees with fans than running the evap during the day and then forcing your A/C to remove all that moisture from the air each and everyday. This makes your compressor run longer, work harder thus running hotter, thereby using a lot more juice. Just something to think about,

System2 · April 2009

Re: Sun 90 solar panels

So much great info, I hope you don't mind me asking something real simple. A single SUN-90 panel is a great size for me, keeing a 1 or 2 250AH marine batteries topped up for photography and laptop use in the wilderness. Not knowing much about electricity, i'm confused about the positive ground on the SUN-90 panel. All I do is drop a battery or two in the van, and run a small inexpensive 400 watt 12/110 inverter from it. Occasionally I fire up the van and tie the battery in for emergencies, or believe it or not, run a small generator with a battery charger hooked to it. (no 12 volt on the gen).

Would the positive ground requirement of the SUN90 matter if simply used to charge a marine battery (or bank of two). Or would it even work? And if anyone knows a canadian vendor that would be great. thanks in advance. regards, bloort.

icarus · April 2009

Re: Sun 90 solar panels

Bloort,

Welcome.

I will comment on what I know. First,,, I think that the Sun Panels are only available from Sun Electronics in Florida. They are a private label panel.

As far as the positive ground issue. The reality is IMHO it really isn't going to make enough of a difference to you to warrant worrying about. If you are charging a stand along battery that is itself not grounded (either negative or positive) you MAY see a slight decrease in output,,, as much as 10% according to some opinions. Having said that,, I think it is possible that the issue has been resolved and therefore is a non-issue. So even if you do see a reduction, my question to you is,, is the inexpensive price of the panel outweighed by a potential reduction in output by as much as 10%. There is no danger of damaging the panel or the battery,, as it has been explained to me, the panel itself builds up a static charge,, reducing it's output until that static charge is dissipated by grounding.

I think the same basic information holds true if you are going use the panel to charge the negatively grounded battery in the van.

Does this make this clear as mud?

Tony

Sun 90 solar panels

Comments

Categories