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?

[pianotuna]

Hi seraphim,

36 volts has the advantage of thinner wire and lower line losses. With thick enough wire losses could be under 1%.

24 volts has the advantage of slightly more efficient mppt operation (1% maybe?).

If I had to choose between them I'd go 36 volts myself.

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. Sounds like I'm getting different feedback from different people; sometimes from the same person lol.

[seraphim]

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.

[MrWizard]

Are you looking for 100% replacement of your average daily draws? IOW, perpetual solar autonomy?

nope, my 505w is nice but with a residential fridge and heavy PC use, and 4 fans running
i still run the generator some

a 1000w would do it as long as the weather good

[full_mosey]

seraphim wrote:

Mixing panels can bring problems. Let's strive to keep a single 24V panel type.

Same manufacture, same voltage - what type of problems?

Same Voltage, different Imp, can be put in parallel.

Different Voltage, same Imp, can be put in series.

With 4 x 100W and 2 x 150W, your only choice is all in parallel at 24V.

Some like to use series which could use 2 for 48V, 3 for 72V, etc. The MPPT 45 and 60 can take up to 4 24V in series. While you can place all 6 in parallel, you need to be sure you want 24V wiring.

The main reason for higher Volts/series, is that it allows for smaller wire to the controller. Smaller wire is cheaper, plus easier to route because it is more flexible. Is it possible that 6 x 100 would be workable. This could be wired at 36V by placing 3 in series for two arrays of 36V, then these two could be wired in parallel to double tha Amps. You would get the same total Watts.

Another advantage is that you could also decide on 8 x 100W in a 48V setup and the MPPT 60 controller.

I just wanted you to know the options.

HTH;
John

[BFL13]

"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. As soon as solar wake up an hour later batt voltage is in the low 13s and from breakfast to supper time (when usage knocks voltage back down but sun is sinking in the west) high voltage is in the mid 14s (with PWM, my set-up)

So there would never be a time for MPPT to shine as it would in theory with batts in the low 12s.

Some other scenario, much contrived wrt real life, could indeed show why you should $pend on MPPT. Not me! (Except for the fake MPPT I ordered thanks to RJ, for $13----which I will test out of course, completely unbiased as I am, and report on here. BTW, thanks a heck of a lot RJ !!! 🙂 🙂

[seraphim]

Mixing panels can bring problems. Let's strive to keep a single 24V panel type.

Same manufacture, same voltage - what type of problems?

[full_mosey]

BFL13 wrote:
Yes Isc of a 100w panel should be about 6.3a and you will get that with PWM when panels pointed and sun high enough in blue sky.

Tee hee, snicker, snicker, Full Mosey is starting to sound like me wrt MPPT! 🙂

Hey man, I always thought I was the one that helped you understand MPPT! 🙂

Salvo is the one that eventually got through my thick skull on how to properly compare MPPT to PWM.

In short, MPPT excels in low temp, low battery SOC% situations.

Thanks to smk, I now know that the MS MPPT can switch to PWM when it is better. I am taking another look at the MS MPPT 15 for my 170W array. The entry fee for that controller is ~$200.

MPPT could be an advantage this winter in Quartzite.

HTH;
John

[seraphim]

John

Only if it's possible lol

[BFL13]

Yes Isc of a 100w panel should be about 6.3a and you will get that with PWM when panels pointed and sun high enough in blue sky.

Tee hee, snicker, snicker, Full Mosey is starting to sound like me wrt MPPT! 🙂

[full_mosey]

seraphim wrote:
Mr Wizard

I was wondering about that as well - filling up the roof. Trying to decide if it was worth it.

Agin, The AM panels are expensive but I could fit the four 100 watt panels, plus 2 150 watt panels alongside the AC (possibly-have to do a closer roof inspection.). It's nice those AM panels are narrower.

Mixing panels can bring problems. Let's strive to keep a single 24V panel type.

How about extra panels as awnings? 🙂

Are you looking for 100% replacement of your average daily draws? IOW, perpetual solar autonomy?

HTH;
John

[full_mosey]

pianotuna wrote:
Isc = 6.29 amps @ short circuit


However they are $300 each.

Ouch, no go!

Anyway, at full tilt, 4 x 6.29 = 25.16 even when hot. That doesn't leave much room for MPPT to improve upon.

Thanks;
John

[pianotuna]

Hi seraphim,

700 watts would not be wasted--if you follow the siren song of an inverter *grin*.

[seraphim]

Mr Wizard

I was wondering about that as well - filling up the roof. Trying to decide if it was worth it.

Agin, The AM panels are expensive but I could fit the four 100 watt panels, plus 2 150 watt panels alongside the AC (possibly-have to do a closer roof inspection.). It's nice those AM panels are narrower.

[pianotuna]

Hi seraphim,

I'd probably use the "string" calculator at the morningstar site. I'd probably buy the Rogue controller, and I'd probably max it out wattage wise.

[seraphim]

Pianotuna

I figured the numbers wouldn't be completelty accurate, but just ran them for comparison. Which configuration would you use, given the choices?