House/solar battery opinions

[seraphim]

My current battery space is 20"L x 14"w x 10"H

Going solar, and want to packs as much AH in there as I can (reasonably). Currently looking at 250 - 300. Price is not THE deciding factor, unless all else is equal.

I don't have experience with a lot of different companies, so I don't know who may a poor reputation. Some I am looking at:


http://www.apexbattery.com/group-8d-gel-solar-battery-solar-batteries.html $609 + $109 shipping)

http://www.atbatt.com/product/23216/sla/power-sonic/12v-150ah/battery#tabs ($774 for 300ah no nipping)

http://www.batterygiant.com/Product/8D%2DGEL (allegedly $577 (maybe $669) for 225AH can pick up locally)

http://www.mastervolt.com/marine/products/agm-slimline-12v/agm-sl-12-150/#specifications (can fit 2 185AH units in my space - haven't found an online price yet, which tells me something lol)

Any thoughts on these, or others you are aware of?

[mena661]

smkettner wrote:

If it is just about saving money.... good luck. Better to just get the right equipment from the get go.

I have limited roof space. I want to be efficient in filling it, that's all. I would rather have one 300W panel and another 140-170W than three 140W panels or two 140's and one 170W. Both would take up the same amount of space (300W vs two 140W's) but the 300/140-170 combo puts out more watts overall. It would be a waste of money for me to buy a 30A Rogue for just the 300W for example because any subsequent panel couldn't be added to it unless the Vmp was really closely matched and most of the small panels are NOT 30+V. I might end up wasting watts potential because of controller expense. I thought I had a roof pic already but I'll take one tonight and post.

[pianotuna]

Isc = 6.29 amps @ short circuit


However they are $300 each.

full_mosey wrote:
PWM controllers use the Isc, not the Imp for charging current. Isc is 10-20% higher than Imp. Sometimes MPPT cannot even beat that!

What is the Isc of the 100W panels?

If we are going to eliminate PWM, let's do it right.

HTH;
John

[full_mosey]

smkettner wrote:
Morningstar MPPT will choose PWM if output is higher. Nothing to lose.

Sweet!

HTH;
John

[time2roll]

Morningstar MPPT will choose PWM if output is higher. Nothing to lose.

[full_mosey]

PWM controllers use the Isc, not the Imp for charging current. Isc is 10-20% higher than Imp. Sometimes MPPT cannot even beat that!

What is the Isc of the 100W panels?

If we are going to eliminate PWM, let's do it right.

HTH;
John

[MrWizard]

i think exspanion is dictated by sq ft of roof vs panels not number of watts
2*140 should take almost the same sq ft aka number of cells as one 300w

its easier to position multiple smaller panels that a few large panels

also from experince all this 'partial panel shading' comments don't mean much in real life use in the summer time

multiple 'parallel' panels suffer a small loss when one panel has a little shade from the A/C unit
no big deal.. its still more total power than you would get if that panel was not there.
NOTE I SAID PARALLEL

shading will mean more to snow birds in Az in the winter, but hey, thy can tilt them if they want

i would rather have a roof full of panels that ocassionasly get some reduced output than only a couple of perfectly mounted panels, my over all power gathered is greater

If i was designing a new system
it would be muliple 24v panels in parallel' with mppt contoller
and as many watts as i could get on the roof 'shading be danged'

mena661 wrote:

smkettner wrote:
Why would this be helpful? Not a best practice even if it works.

I was asking because I'm interested in that ETSolar 300W module which would be borderline with the 20A Eco-worthy MPPT controller. I figured maybe buying two of those and run them in parallel. It would be FAR cheaper than buying one 30A Rogue or the 45A Morningstar. I'd much rather have one 300W than two 140W units although the two 140's might be much cheaper. One 300W allows me to expand some in the future where two 140's might not allow that.

[pianotuna]

Hi seraphim,

The numbers are not going to work as you hoped.

It is a bit more complicated. On an 18.5 volt panel MPPT is not going to give you nearly the gain you calculated.

You might well get more by going series/parallel on the panels so that input voltage to the mppt is 37 volts.

The PWM calculation is also too high.

seraphim wrote:
Let's do a comparison with the the Helios 300 watt 8.2 amps at 36.55 volts and the AM 100 watt 5.42 a,ps at 18.5 volts lets use 12v as the charging voltage for ease of calculations (there, PT, I said it lol).

Helios though an mppt 36.55/12*8.2 = 24.9758 amps

AM through mppt (18.5/12*5.42)*4 = 33.42 amps

AM through PMW 5.42*4= 21.68 amps

Ok. I'm man enough to admit I'm wrong. The AMs will put out more amps through the mppt. I didn't 'calculate' their higher voltage through an mppt - just the PMW.

Theoretically, with the 4 panels in a three hour period, I could generate enough amps to recharge a day's usage of 100 amps. It's going to cost me an additional $500, but...

I concede defeat

[seraphim]

Thanks to everyone for putting up with me lol. I can be a PIA at times.

[seraphim]

SteveAE

Went out this morning and the numbers hadn't changer (apologies it was .1 amp). Changed P1 to 13.5, and the green light began flashing indicating a full charge, amps remained unchanged and battery showed 100%. Unplugged from 110, turned on a light, and amps changed to 2.7. Everything appears fine. Guess the battery was as fully charged as it was going to get, so it really wasn't drawing any amps.

Thanks for the suggestion.

Battery may have lost some capacity, but it should still tell me what I want to know.

[seraphim]

"If it is just about saving money.... good luck. Better to just get the right equipment from the get go."

Yes.

Also, just caught your answer to my earlier question - thanks.

[time2roll]

mena661 wrote:

smkettner wrote:
Why would this be helpful? Not a best practice even if it works.

I was asking because I'm interested in that ETSolar 300W module which would be borderline with the 20A Eco-worthy MPPT controller. I figured maybe buying two of those and run them in parallel. It would be FAR cheaper than buying one 30A Rogue or the 45A Morningstar. I'd much rather have one 300W than two 140W units although the two 140's might be much cheaper. One 300W allows me to expand some in the future where two 140's might not allow that.

If it is just about saving money.... good luck. Better to just get the right equipment from the get go.

[seraphim]

Thanks for the explanation, Don

[seraphim]

Let's do a comparison with the the Helios 300 watt 8.2 amps at 36.55 volts and the AM 100 watt 5.42 a,ps at 18.5 volts lets use 12v as the charging voltage for ease of calculations (there, PT, I said it lol).

Helios though an mppt 36.55/12*8.2 = 24.9758 amps

AM through mppt (18.5/12*5.42)*4 = 33.42 amps

AM through PMW 5.42*4= 21.68 amps

Ok. I'm man enough to admit I'm wrong. The AMs will put out more amps through the mppt. I didn't 'calculate' their higher voltage through an mppt - just the PMW.

Theoretically, with the 4 panels in a three hour period, I could generate enough amps to recharge a day's usage of 100 amps. It's going to cost me an additional $500, but...

I concede defeat

[pianotuna]

Hi seraphim,

It takes 60 watts per 100 amp-hours of panels to be able to equalize a battery using solar. In my opinion, that is the bare minimum number for wattage in a well designed system. So 480 amp-hours X .6 = 288 watts.

seraphim wrote:
I'm confused here. How'd you jump from amps (480) to watts? Is .06 a magic number of which I don't know the significance lol?

[mena661]

smkettner wrote:
Why would this be helpful? Not a best practice even if it works.

I was asking because I'm interested in that ETSolar 300W module which would be borderline with the 20A Eco-worthy MPPT controller. I figured maybe buying two of those and run them in parallel. It would be FAR cheaper than buying one 30A Rogue or the 45A Morningstar. I'd much rather have one 300W than two 140W units although the two 140's might be much cheaper. One 300W allows me to expand some in the future where two 140's might not allow that.