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?

[seraphim]

Whew. Thank you for the explanations. Give me time to process them lol.

[2oldman]

seraphim wrote:
Is 36v 300 watts better than 24v 300 watts? I originally thought so, now I don't know.

No, not in power anway.

[full_mosey]

seraphim;

Hang in there. Understanding daily battery draws is trivial compared to understanding solar recharging.

This concept of how to connect panels/modules takes a while to grasp.

Here are two runs of the MS string calculator.

1. 102W 24V modules

2. 102W 12V modules


The modules I found are 102W, but one is 12V and the other is 24V. That is close enough for discussion.

Note the min Vmps for the 816W squares. I set the min temp to 15C to allow the extra 2W to work here.

With the 24V modules there is only one choice, 4 strings of 2 series modules each giving a 48V nominal system. Mouse over the 816 cell. The actual min Vmp is 53V+. If you size wire for 48V, you will always have adequate wiring for best Watts to arrive at the controller. There will always be losses no matter what size wire due to resistance. There are wire sizing websites to help choose wire size.

For the 12V modules there are two choices. You want the 2 strings of 4 series modules = 48V because you will always have 55V+ and 48V sized wiring will always be adequate. The other 4 x 2 array needs 24V wiring which will be larger and not necessary.

The final answer is that either 12V or 24V panels, or any Voltage, can be configured to achieve useful arrays. They do have to fit the roof real estate, though.

HTH;
John

[mena661]

smkettner wrote:
I would take 600w over 300w.

X2

[Almot]

seraphim wrote:
Is 36v 300 watts better than 24v 300 watts? I originally thought so, now I don't know.

I thought I understood the possibilities of higher voltage panels, now I feel confused again.

Seraphim, guys here are very technical. There are benefits to 36V panels over 24V panels of the same wattage. And there are benefits of 24V panels over 12V panels, but in your case they don't outweigh the benefits of 33% more wattage of 4*100W compared to one 300W.

For 400W you will need 35A-45A controller. 60A controller would work too, but this would be waste of money, IMO.

[full_mosey]

pianotuna wrote:
Hi BFL13,

Magic blue smoke anyone?

MPPT on a 17 volt panel will get you 8%, on higher voltage it will do better than that.

Yes, I believe I can get better than 8% in Quartzite, AZ during Jan-Feb and with low SOC% batteries at morning. That is how MPPT works best.

There is nothing to lo$e if the MS MPPT can choose PWM on the fly if it determines Isc will be more Amps. I do expect more total daily harvest.

I will rewire the 2 x 85W panels into series so that more solar Volts will get to the controller at 24V as opposed to the current 12V parallel configuration.

HTH;
John

[pianotuna]

Hi seraphim,

You asked what I would do. If I take you at your word that no large inverter use is in your future, and that you have led lighting, I'd go with about 300 watts of solar with the 480 amp-hour bank. I'd do a flat fixed install.

I'd look at my budget and if there was enough funds I'd buy a Rogue controller. If there was not then I'd get the Morningstar NON mppt controller with a temperature probe.

But, I am not you. I'm considering adding "wings" so I can double or perhaps triple the solar I do have. I have enough for my original "tasking", but I'm very nearly full time now and it was 34C (94 F) on Monday. That means running a generator or finding some shore power.

If I add the wings I may be able to run the air conditioner from the panels.

[pianotuna]

Hi BFL13,

Magic blue smoke anyone? I believe the Blue Sky manual suggests 125% of panel capacity.

MPPT on a 17 volt panel will get you 8%, on higher voltage it will do better than that.

BFL13 wrote:
OTOH, it seems that MPPT controllers clip their amps at max rating so you can ignore that 20% margin.

It seems that within the usual operating range of 13-14.4 batt voltages, MPPT might maybe get you 8% more than PWM maybe.

[pianotuna]

no, but I'd go for 2 300 watt 36 volt panels instead of 6 100 watt ones.

seraphim wrote:
So can I also assume you'd prefer the 300 wat 36v over 6x100 watts at 12 volts?

[BFL13]

Here is how I calculate max amps per watt of panel for deciding how much amps the controller and its fuse needs.

with PWM you get Isc of the panel and you are supposed to allow for 20% more. 130w panel gets 8.2 isc. it is proportional.

this means your 20a PWM controller can handle about 250w of array and be within the 20% margin.

OTOH, it seems that MPPT controllers clip their amps at max rating so you can ignore that 20% margin.

It seems that within the usual operating range of 13-14.4 batt voltages, MPPT might maybe get you 8% more than PWM maybe.

Here, you can get 12v panels for 1.08/w. they are a bit more in the States due to the tariff on Chinese stuff. Somebody on here in the States said they paid 160 for a 100 (wow!)

[full_mosey]

seraphim wrote:
To run 24 volt panels on my available space limits me to one panel about 300 watts (that I've found so far. The 100 AM solar panels (12v) are the only ones narrow enough to fit multiple panels. Supposing I could run two series of three I'd get 300 watts at 24 volts. I could find a 36 v panel at 300 watts which also fit the area. These are my options. Can't do four 24v 100watt panels - that I've found. Or am I misunderstanding you?

Is 36v 300 watts better than 24v 300 watts? I originally thought so, now I don't know.

I thought I understood the possibilities of higher voltage panels, now I feel confused again. Sounds like I'm getting different feedback from different people; sometimes from the same person lol.

I thought the 100W panels were 12V nominal. If so, then:

12 + 12 + 12 in series = a 36V panel at 300Watts. Two of those in parallel is 36V and 600 Watts and a perfect match for the MPPT 45.

4 x 12 in series = 48V and 400W. Two of these in parallel is 48V and 800W and a perfect match for the MPPT 60. Plus even thinner wiring!

HTH;
John

[time2roll]

seraphim wrote:
So can I also assume you'd prefer the 300 wat 36v over 6x100 watts at 12 volts?

I would take 600w over 300w.

[full_mosey]

BFL13 wrote:
"In short, MPPT excels in low temp, low battery SOC% situations"

I find that with usual usage and battery bank etc, etc, morning voltage before solar wake up is in the high 12s. ...

Some other scenario, much contrived wrt real life, could indeed show why you should $pend on MPPT.

You have a 458AH bank, that is why your morning Volts and SOC% are so high and that MPPT has little to add. No real value for you.

I have two banks. 79AH with a 130W panel and 110AH with a 170W array. It is common for me to wake up to 50% SOC where extra current can be harvested. Granted, they will be expen$ive Amps. That is not contrived.

HTH;
John

[seraphim]

So can I also assume you'd prefer the 300 wat 36v over 6x100 watts at 12 volts?

[seraphim]

Pianotuna

Thank you. The string calculator - to date - is not telling me anything I understand, which is why I asked you which of the options you'd choose earlier. Lol