Newbie looking for advice for dual battery bank solar setup

[Logan005]

if you are paralleling battery strings, you are likely selecting the wrong battery for your application, consider 24 X 2 volt L-16 style batteries all in series = 48 volts nom and no paralleling.

[Tarlak333]

I have revised my power budget and it will be 2KWHr/day.

So at this point I only need about 18KWHr of battery bank, and am scaling down to a 24V system. Longevity of the battery bank is not a significant factor, looking for 1-3yrs optimal life span, max 5yrs. Up front cost is a major factor. I was looking at 6 of the J185P-AC (12V 250AHr each = 18KWHr total) I can get these for $1991 w/ shipping. Wiring would be simple 3 parallel sets of 2 batteries in series. (6 long wires up to disconnect switch and 3 short wires for battery to battery connections).

With 1300W of SolarWorld 325 panels (4 panels) (2 sets of 2 panels in series, each set connected in parallel to the charge controller)

Panel specs: http://www.directsolarsupply.com/sol...-xl-325w-mono/

I'm planning on running a 4.1cuft mini-fridge/freezer and a few led lights and a water tank pressure pump & small fan occasionally at night. During the day during peak sun times I might run a small window AC unit , and occasionally a few small kitchen appliances and a full size washing machine (1-2x week)…..I think this will be a good plan to conserve battery power for only the essentials, refrigeration, water pressure and light at night or during cloudy days. (And keep my DoD to a minimum)


Still looking for:

A small reliable (LP / Gasoline) generator under $1000.
Been eyeing this one but can't find a good deal on it: http://www.yamaha-propane-natural-ga...m/ef1000is.htm


Charge controller
Was looking at: http://www.renogy-store.com/20-Amp-M...trl-mppt20.htm (I just spoke with Renogy and they think this would be ideal for my solar setup....what are your thoughts?)

Good 110-120V 2500-3000W inverter (wired no AC outlets needed, low battery auto shut off a must, and generator auto start would be nice but not necesary)
Was looking at: http://www.amazon.com/Power-PICOGLF2...S+24V+inverter
I like the features but I don’t think I will need a pure sinewave inverter, since I don’t plan on running sensitive electronics. Wouldn't a modified sine wave inverter be cheaper and work for my appliance needs? The price about $200 more than I'd like to spend.

Good battery bank monitoring system.


Well that’s it so far, your help is greatly appreciated

[Mike90250]

1300 w of panels @ 26V charging voltage (24V battery bank) is 50A of charge coming out of the array. 48V would be a better choice if you want a small controller. Apparently the store you spoke to is not well informed about their 20A product.

Batteries - 3 parallel sets of AGM is a time bomb waiting to go. You are warned. Again, 48V reduces the temptation to use parallel banks, but it's your $$

Auto start capable generators, rare below 5Kw. Don't limit inverter choice if you have only a manual start genset.

2500 - 3000 w inverters, marginal @ 24V, better @ 48V.

[Tarlak333]

Mike90250,

Thank you for all the resource & technical links, I'm going to start reading up now. Please see my comments below.

1300 w of panels @ 26V charging voltage (24V battery bank) is 50A of charge coming out of the array. 48V would be a better choice if you want a small controller. My mistake I was thinking the input current to the charge controller would be under 20A @ 74V.....but didn't think about the current coming out at 24V to the battery bank....ooops duhhh.

Apparently the store you spoke to is not well informed about their 20A product. I spoke to a Renogy factory technician...however he seemed young and inexperienced & didn't really seem too know the product that well......I wasn't filled with confidence.

Batteries - 3 parallel sets of AGM is a time bomb waiting to go. You are warned. Again, 48V reduces the temptation to use parallel banks, but it's your $$ The batteries I was looking at are not AGM they are Flooded/wet lead-acid batteries. Also why does everyone keep pushing for series connections??? What's up with that? I I've read nothing at all anywhere that says to avoid parallel connections. Please let me know if there is a scientific reason why ppl a pushing series connections for battery banks. Thank you.

Auto start capable generators, rare below 5Kw. Don't limit inverter choice if you have only a manual start genset. Good to know just thought it would be convenient, I'm trying to keep the propane generator purchase to under $1K. Thank you.

2500 - 3000 w inverters, marginal @ 24V, better @ 48V. That's what I thought....that's why I was originally planning on going with a 48V system. But thought I could scale down cost a bit with a 24V system.

[sensij]

Mike90250,

Thank you for all the resource & technical links, I'm going to start reading up now. Please see my comments below.

For more info on series vs parallel batteries, read this.

And also this, here is blunder #4:

BLUNDER #4 Many Small Batteries in Parallel Strings

The ideal battery bank also is the simplest, consisting of a single series string of cells that are sized for the job. This design minimizes maintenance and the possibility of random manufacturing defects. Suppose you require a 700‑amp-hour (AH) bank. You can approximate that with a single string of 700 AH industrial-size batteries, or two parallel strings of 350 AH (L-16 style) batteries, or three strings of 220 AH (golf cart) batteries. The diagram below shows these three variations.
A common blunder is to buy the smaller batteries because that approach is less expensive up front. The problem is that when current splits between parallel strings, it’s never exactly equal. Often, a slightly weak cell or terminal corrosion will cause a whole battery string to receive less charge. It will degrade and fail long before other parallel strings. And because partial replacement aggravates inequalities, the only practical solution is to replace the entire battery bank. One way to reduce or avoid parallel battery strings is to use the highest DC voltage standard that is practical. The same batteries that would form two strings at 24 V can be wired all in one string for a 48 V system (now a common standard). The quantity of energy storage is the same, but the layout is simpler and the current at critical junctures is cut in half.
If you must have multiple battery strings, avoid stacking cable lugs at the battery terminals to make parallel connections. Instead, bring wires separately from each string to two bus bars outside the battery box. This reduces corrosion potential and helps create electrical symmetry.

Also, from here:

Why series?

Series arrangements may mean fewer cells which may allow for more stuff for greater capacity or they can be built more rugged in a given amount of space. A series arrangement also means that a weak cell does not sap the energy of the others as any current going through the battery will just pass through a weak cell. This fact, that any load or charge current goes through all cells equally, tends to keep all of the cells at an equal state. It also means that a failed cell does not cause internal circulating currents. The failed cell may add some resistance (which does sap energy, but only when a load is applied) and, since it does not contribute any voltage, it will show as a reduced battery bank voltage.
Why parallel?

A parallel arrangement means that current is shared between batteries and this means that each battery is exercised less vigorously which may increase usable capacity. Since removing any single battery will not change the voltage, there is a redundancy in batteries that can be useful in the event of failure (if that failure is detected early enough). Parallel is also useful in low voltage systems because it may be easier to find batteries at needed supply voltages. A failed cell in a parallel bank will sap energy as the other cells try to charge it (all the time, which adds up in sapping energy). This can cause heat and loss of water in the failed cell that run a battery down by itself.

[Tarlak333]

PERFECT!!! I am now wiser in the ways of series vs. parallel battery banks.

A series arrangement also means that a weak cell does not sap the energy of the others as any current going through the battery will just pass through a weak cell. This fact, that any load or charge current goes through all cells equally, tends to keep all of the cells at an equal state.

This was the part I didn't understand, great info, Thank you.

So with my new knowledge in hand what do you guys think of this: Eight (Surrete Rolls S-480 6V 375AH in SERIES (YAY) to give me my 18KWh target battery bank size. (and ~3.5days of autonomy)

(Surrete Rolls S-480 6V, 486AHr @ 100Hr rate, WOW) = 23,328WHr = ~5 days of autonomy @ 2KWHr/day

[Amy@altE]

I would be careful about the SW320, being 24V (72 cell) panels in the hot NM sun. With most charge controllers,you'd only be able to do strings of 2, and when it is blazing hot out, you may have trouble getting a high enough voltage for a really good charge. With a Vmp of 36.7 x 2 = 73.4Vmp. You may be better off with strings of 3 of their 280W 20V (60 cell) panels, Vmp 31.2 x 3 =93.9Vmp. You'd never have to worry about not getting a high enough voltage. Most locations would be fine with two 24V panels in series, but I get concerned in the extreme heat of NM.

[Tarlak333]

Current backup power system specs:

Generator Yamaha EF2000iS Tri-Fuel 2000W (1600W continuous) (~$1,000)
6 SolarWorld Sunmodule Pro XL 325W Panels (2 strings of 3) (~$2000 w/ shipping)
8 Crown CR-430 Wet Cell Deep Cycle (25200WHr) ($233/ea w/ shipping straight from factory, WOW)
AIMS 48V 2000W inverter/charger (1600W continuous, 6000W surge) ($628 Amazon w/ shipping)
Midnite Solar Classic 150-SL MPPT Charge Controller ($595 AltEStore w/ shipping)
Misc cables, panel mounting hardware, breakers, etc... ~$600

This puts me at right about $6,500

What do you all think of this setup?

Thanks

[sensij]

Batteries... 430 Ah * 6 V * qty 8 = 20640 kWh.

Inverter.. for me, no UL or equivalent listing would disqualify it from consideration.

[Tarlak333]

Did you even look at the battery link? (100 hr rate is 525AH)

Can you suggest a comparable 2-3kW inverter charger? That's not over $1000

[sensij]

Did you even look at the battery link? (100 hr rate is 525AH)

You are right, I missed in the thread where you said your discharge rate would never exceed 5.2 A, so the 100 hr capacity would apply. 5.2 A * 48 V = 250 W max when you are running at night or in poor sunlight.

[sensij]

Also, from the same site you linked the 325 W panels above (assuming they have good shipping, or something), you could go with the 260 W Hyundai panels and get more power for less money.

[wqp1107]

I am a supplier for solar system, if you have any demand on solar panel,solar mounting, solar battery, solar cables,solar inverters, please feel free to contact me, I will quote and give suggestions while in installations from 1KW to 1MW, off-grid and on-grid.
Alex

Mod note. If you wish to advertise here, contact user JASON for ad rates.

[Mike90250]

> Misc cables, panel mounting hardware, breakers, etc... ~$600

Does that include the PV racking ? Seems low.

[Tarlak333]

Thanks wqp1107, will do.

Sensij,

Looking at the Hyundai 260 vs. the SolarWorld 325 panels the SolarWorld appears to be the better build panel, SolarWorld appears to have about the same or better specs except for the TCVoc which the Hyundai is much better.

Crunching the numbers this is what I get:

	TCV	TCP	NOCT deg C	Vmp	Imp	Imp total	Vmp total	P (Wtotal)
(6) SW325	N/A	N/A	46	37.00	8.84	17.68	111.00	1962
(8) H260	N/A	N/A	46	31.10	8.40	16.80	124.40	2090
	TCV	TCP	Hot OT deg C	Vmp	Imp	Imp total	Vmp total	P (Wtotal)
(6) SW325	-0.00304	-0.0043	76	36.91	8.71	17.42	110.73	1929
(8) H260	-0.00121	-0.0045	76	31.06	8.27	16.53	124.25	2054

The 8 H260s would cost me ~$300 more w/ shipping and would require 2 more mounts and wiring (more $$), but would give me about 15V more per string and about 130W more power total.

I don't know if that would be worth it for a slightly inferior panel and more work & $$ to setup. I do see the benefit of having the 4 panel series strings producing the higher Voltage, this gives me another data point to investigate....I'll keep shopping around and see what I can find.

Thanks