OFF GRID POWER; various thoughts on...

[alex trent]

Any straight forward reason not to use one PV panel.

I have to bring in country...so one high capacity panel sized and weight to meet baggage is the best bet.

I am thinking about something in the 200 watt range.  With some luck that can get me by day be day without a generator.  I need about 500 watt hours a day....and at 70% this needs 4 hours a day which I can get 4 months of the year.  This lets me cut the number of batteries I need with just a generator....I figure i can get by on one  120 AH..mostly just to store for some low wattage lights 3 hours at night.

If i get a reefer...that will all change but even at that one other panel can make it work with one more panel.

[MountainDon]

Any straight forward reason not to use one PV panel.

If one covers the requirements, why not. It's not like something that has a high failure rate and because of that you would want redundancy.  IMO

[alex trent]

So after all the whining about not being able to get stuff here, I walk into a "solar" store here ( the one and only) and see two 225 AH Trojan 105 batteries among all the other no name stuff.  $105 per battery and before i can say, I will take them I get a 15% discount (no tax). A bargain at the original price.. I bought them to pick up tomorrow.

They look real...maroon..and all the labels.  What is the downside...cannot ascertain date of mfg. How much can that mean?  I will it have the option of bringing them back.  But at this price, i guess risk is low.

I get my IOTA charger and all the cables from the States next week so i am in business for real and the marine battery and the 10 amp car charger are retired.

[MountainDon]

from Trojan...

How do you read the date codes on the batteries?
Positive Terminal- Manufacturing Date. This code indicates the actual date when mechanical assembly of the battery was completed. At this point, electrolyte has not been added to the battery and formation charging has not taken place. LETTER stands for the month and could be anything from A to L (A=January, B=February, C=March, and so on),; NUMBER stands for the date.
Negative Terminal- Shipping Date. This code indicates the month and year when the battery was shipped out of our factory. LETTER stands for the month (see below); NUMBER is the last digit of the year.

Example: A battery with "I26" stamped on the positive terminal and "J2" on the negative. "I26" means that the battery was assembled, without electrolyte, on September 26th. "J2" means that it was shipped from our factory around October of 2002.

Trojan Link, scroll to bottom

[alex trent]

Thanks..

So, the missing link is how long can a battery sit on the shelf and be acceptable?  Info is owhere to be found.

[alex trent]

Trojan techies say one year from MFG date unless you know the dealer and he has charged regularly.

[MountainDon]

Good to know. Thanks

In some ways it is too bad that batteries are not shipped dry like they all were decades ago. I filled a lot of batteries working in a garage as a kid.

[glenn kangiser]

After they lose their charge sulfation starts setting in on the plates making it hard if not nearly impossible to get full capacity back.  A PWM solar charger/regulator or desulfator unit added can help break up sulfation.  Also EDTA can help to chemically desulfate them.

[AdironDoc]

Considering a situation such as mine where I will be running a 50W 12V panel and hope to power an intermittent use 7.5A 12V pump at the springbox, what is the optimal site for the battery? The springbox is near the bottom of a ravine and cannot be moved. The only consistently sunny area, on the other hand is atop the hill in a clearing some 120ft away. In consideration of inevitable voltage drop, should the charge controller/battery be closer to the PV panel, closer to the pump, or in the middle? It would seem to me that a higher voltage would be better used to charge the battery, as it would require in excess of 12V to fully charge. The Shurflo motor on the other hand, may allow for a bit of drop. Is this so?

[MountainDon]

What is the rated max power amps of the PV module (Imp)?

I'm going to guess; module Vmp approx 17 VDC and Imp approx. 3 amps.

The pump is 7.5 amps at 12 VDC.

If the CC was by the batteries which were located by the pump (120 feet from the module)...
(17 VDC at 3 amps)
...for a 3% voltage drop #6 AWG wire is needed; Cu, Al would be #4
...for a 2% voltage drop #4 AWG wire is needed; Cu, Al would be #3

If the CC and batteries were by the PV module (120 feet from the pump)...
(12 VDC line voltage at 7.5 amps)
...for a 3% voltage drop #2 AWG wire is needed; Cu, Al would be 2/0
...for a 2% voltage drop 1/0 AWG wire is needed; Cu, Al would be 3/0

[MountainDon]

Depending on the CC you have you might be better off with another panel in series. Raising the volts will drop the wire size. But that's not going to work with a lot of charge controllers.



Such is the fun of long wire runs. Try my 325 foot run. That's why I run three in series for 70 to 90 volts from the modules to the distant CC.

[AdironDoc]

Thanks, Don, I hadn't thought about the fact that the panel's voltage is a bit higher. The specs are:
HQRP® Solar Panel Rated Power: 50W; Maximum Power Voltage: 17.2V; Open Circuit Voltage: 21.6V; Maximum Power Current: 2.91A

I had the panel already for another project and wanted to get away with not having to buy much else. Seems your answer is clear. Park the batteries/CC near the pump. The shurflo I have is the 12 VDC, 3.0 GPM, 55 PSI, and 7.5 Amps, 4008-101-E65 3.0 Revolution. It's supposed to dry prime up to 6 feet vertically. If a proper check valve could be fool-proof and keep the pump primed, I suppose in theory I could move the pump at least 20 feet (6 feet vertical) up from the springbox without issue. I'd hate to resort to that as I planned on keeping the pump, valves, etc. tucked in under the roof of the spring-box cover.

Thanks for the breakdown.

Doc

[Dave Sparks]

Don,

I emailed you! Are you going to visit camp oso?

--Dave

[MountainDon]

emailed back just now.

[AdironDoc]

Did anyone catch the news the week before last, about a domestic solar startup company that came up with a innovative design in panels? Don't remember the channel, but I was hoping to get the company name if any of you remember. The anchor was allowed to see basics of the design but the details were said to hush hush until August, when the patented design actually goes into production. Of note, they are using inexpensive single modules arranged in rows. Nothing fancy. Over them, what appeared to be a panel of plastic that their optical production facility originally specialized in manufacturing. They were apparently in the lens/composite industry prior to this foray.  With the plastic panels deeply furrowed with what looked like embedded Fresnel ripples, sunlight in the demonstration struck the modules from almost any angle with high intensity pushing the module to produce multiples of what comparing units would be expected to turn out. The conventional panel alongside it was used to demonstrate the um..glaring difference 

Upshot of it was that the panels cost far less than conventional to produce, take up less than half the space, and turn out 2-3x the output for a given area/footprint. Developer noted it's far less costly to push the output of existing modules using optics than to use more modules. The industry experts interviewed noted this may be the way solar panels all look down the road as a roof's worth of panels could be fit into a much smaller space without as much concern about orientation.

Any development in cost/performance is good news I suppose. Especially good to see its a domestic company. Now if only the prices on good batteries were to fall as well... 

[Dave Sparks]

I have been hearing about "that" company since solar panels went to space. They have become priced reasonable but efficient in differing amounts of radiance is still for space budgets.

I think what you heard was that these panels were extremely black and worked really well in cloud light levels.

[AdironDoc]

Could be. I don't remember the full story about them. I do remember the gist of the piece. As a plastics/lens manufacturer, they took cheap module strips and used a propriatary lens system produced at low cost to ramp up the power while dropping the footprint. They were confident they could beat the $/watt prices of the current Chinese manufacturers. I suppose if it's a winner we'll soon hear of it again. My main concern would be that the way the plastic lenses had troughs, they'd catch any debris landing on them and also how well plastic would hold up over the years.

[MountainDon]

I'd not heard of the report.   I was going to say that I'll believe it in August when I see them.  But then decided to leave it alone.  Then Dave chimes in and more or less affirms my feelings... so there ya' are.... I'll wait till August. This August, let's hope.   

[Dave Sparks]

Yes! Definately August!  The holy grail will be when a panel can gather energy over a day, off axis as well as tracked.

[AdironDoc]

I think that my panels have been slightly exceeding the maximum amperage rating of my Chinese mppt controller but without any issues yet. It's listed at 15 max with recommendations at keeping it safely under 12. My panels should put out 200w at 27.6v but have exceeded that. I figure I've hit at least 16amps between the two of them. So here's my question. If the batteries were completely empty, I can imagine it would pull the full 16 amps. But do the batteries, which are never more than 30% discharged, really allow the panels to push the controller to anywhere near its limit?

[Dave Sparks]

There are two things to consider. The batteries can be full and if your loads are large, the controller will output power until it internally current limits, the panels are maxed, or the circuit breaker trips.

The second is if you have a controller of dubious design, you should conservatively current limit the beast for safety sake. You probably do not want to start a fire.

[AdironDoc]

There are two things to consider. The batteries can be full and if your loads are large, the controller will output power until it internally current limits, the panels are maxed, or the circuit breaker trips.

The second is if you have a controller of dubious design, you should conservatively current limit the beast for safety sake. You probably do not want to start a fire.

Noted, Dave. I just swapped it out with a Chinese 30A 1.2kw MPPT controller. Now I can add my third panel. 200W/27.6V = 7.25A. Three panels will still be well under the threshold even allowing for 20% over output. The only fires I want to start are campfires!

Doc

[OlJarhead]

Best price on quality solar battery?

I'm looking for something to build a 12vdc bank in the 1200 AH range that will last a lot longer then GCB's.

Thoughts?

I'm currently looking at the Surrette S530 400ah batteries to do the job (400ah@20hrs).

Not looking to buy immediately but looking to replace the GCB's in the future and want to plan for it now (budgeting and all that).

Thanks!

[MountainDon]

..... last a lot longer then GCB's.
Thoughts?

That statement makes it sound like the present batteries are not performing well, maybe failing. Or is it simply that they do not have have sufficient rated capacity to do the tasks being asked of them?

[OlJarhead]

That statement makes it sound like the present batteries are not performing well, maybe failing. Or is it simply that they do not have have sufficient rated capacity to do the tasks being asked of them?

They definitely have insufficient capacity I'd say but I need to do more testing.

Life has likely been reduced (I've got to get a hydrometer this week!) due to twice draining them below 80% (actually 100% according to the meters).

I'd like a battery that should last a decade or more if possible and a capacity to run for 4 days without sun while using CFL's, the fridge etc....current usage can be 1700-1900 watt hours per day according to my charge controller and the calculator is telling me that I need up to 16 GCB's or 10 L16's (@370AH - default on spreadsheet).

I was looking at some Surrettes at 400AH (20hour rating) and I would need max 8 of them according to my load -- 1600AH -- and one more panel to keep them charged up.....I think I priced them at $2800 for 8 and they have a 7 year warranty on them.

My thought is that I need more battery bank power, can't add more batteries now since the bank is two years old (just) and the GCB's while 'ok' for me so far will eventually need to be replaced anyway.  So I figure if I plan to get the bank now I can get it in the budget and acquire the batteries in less of a hurry then I might need to do in a year or two