Remote Powered Location

Valus · June 2011

So awhile back I setup a Remote Location with some wireless monitoring equipment with a Panel and related equipment.

However my needs have changed as far as power consumption. i'm now pulling more power then the panels are producing and i'm losing power at this location at times.

At 1st i bought 1 40watt panel with 2x 79amp batteries and a morning star pro 30, which i then upgrade to a 80watt panel with 2x Deka 200amp batteries(all 12volt bateries).

(However the 80watt panel had some issues just in the last few weeks which i ha dto pull and temporarly put the 4owatt bakc on it.)

I'm now realizing again roughly 2 years later i'm running into the same issue not enough power(due to equipment upgrades). SO i went ahead an purchased a 135watt panel.

Now i had a custom box made to put all the batteries/invertor and the morning star unit.

However i need to prepare for winter time and roughly up to a month to 3 months of fog where i live.

i'm currently pulling almost 20watts load(1.9amps accoring to the morning star and currently only producing 1.7amps with current 40watt panel).

now my question is since i'm not good with the math and i sum how fudged it up twice. Exactly how many batteries would i need to be able to sustain say 1-3months of fog(still light out just no direct sunlight). I can currently put 4x Deka 200amp 12v batterie sin this box stacked. but i'm guessing that wouldn't be enough.

I'm thinking about buying another box to be able to place more batteries in.

I also have acable run from the solar unit to the morning star at roughly 75ft in cable length.

What woudl be an idle setup or something i can slowly upgrade to???

some suggestions would be helpfull.

I've currently purchased everything from your site so far and I wa slooking to buy some more of the Deka 200's but now being face dwith the concord equiv.

bmet · June 2011

Re: Remote Powered Location

I am not good with the math either, but it is clear to this novice that you have not enough panel and too much battery, might even be chronically undercharging them to failure. A charge rate of 5 - 13% is usually recommended, altho you should check any documentation that may have come with your Deka's to be certain.

Are you running your two Deka 12V, 200AH batteries together, or is one a backup? IF you connected them in parallel, that's 400AH of battery that can't be properly maintained by your 40W panel. Unless you suspect battery failure, I wouldn't be buying any more. You need more panel, but I'm fuzzy on the math so will defer to smarter folks.

Valus wrote: »

So awhile back I setup a Remote Location with some wireless monitoring equipment with a Panel and related equipment.

However my needs have changed as far as power consumption. i'm now pulling more power then the panels are producing and i'm losing power at this location at times.

At 1st i bought 1 40watt panel with 2x 79amp batteries and a morning star pro 30, which i then upgrade to a 80watt panel with 2x Deka 200amp batteries(all 12volt bateries).

(However the 80watt panel had some issues just in the last few weeks which i ha dto pull and temporarly put the 4owatt bakc on it.)

I'm now realizing again roughly 2 years later i'm running into the same issue not enough power(due to equipment upgrades). SO i went ahead an purchased a 135watt panel.

Now i had a custom box made to put all the batteries/invertor and the morning star unit.

However i need to prepare for winter time and roughly up to a month to 3 months of fog where i live.

i'm currently pulling almost 20watts load(1.9amps accoring to the morning star and currently only producing 1.7amps with current 40watt panel).

now my question is since i'm not good with the math and i sum how fudged it up twice. Exactly how many batteries would i need to be able to sustain say 1-3months of fog(still light out just no direct sunlight). I can currently put 4x Deka 200amp 12v batterie sin this box stacked. but i'm guessing that wouldn't be enough.

I'm thinking about buying another box to be able to place more batteries in.

I also have acable run from the solar unit to the morning star at roughly 75ft in cable length.

What woudl be an idle setup or something i can slowly upgrade to???

some suggestions would be helpfull.

I've currently purchased everything from your site so far and I wa slooking to buy some more of the Deka 200's but now being face dwith the concord equiv.

Cariboocoot · June 2011

Re: Remote Powered Location

bmet is spot-on; this system is way out of balance.

Let's start with the loads. If you're using 20 Watts continuous for 24 hours, that's 480 Watt hours. If this is a 12 Volt system, that's 40 Amp hours of power which needs at least 80 Amp hours of battery. 160 would be better. So why isn't 200 handling it? Because the panel is far too small.

Let's look at the charging. With the minimal 80 Amp hour battery you want to try for a 10% charge rate: 8 Amps. 8 Amps @ 14.4 Volts charge is 115.2 Watts. Since panels don't put out their rating but rather a lower average power, that 80 Amp hour battery would require 150 Watts of panel (based on typical 77% efficiency).

Then there's the harvest: if you get 4 hours of "equivalent good sun" per day that panel would yield 460 Watt hours daily - short of the expected consumption. Add in foggy weather and you may be very, very short on panel.

In other words you've been chronically undercharging batteries, resulting in their early demise.

For one of those Deka 200 Amp hour batteries you should have:

20 Amps @ 14.4 Volts = 288 Watts, less derating = 374 Watts of panel. At least. The 75' of cable could be significant on Voltage drop, and the foggy weather could be murder.

Here's some of the standard references to help you get a handle on it all:
Battery FAQ's http://www.windsun.com/Batteries/Battery_FAQ.htm (The basis of any off-grid system.)
Voltage drop calculator: www.solar-guppy.com/forum/download/voltage_drop_calculator.zip (Check the loss on that 75' run.)
PV Watts: http://www.nrel.gov/rredc/pvwatts/ (See what sort of power you can expect to get in your area.)

Valus · June 2011

Re: Remote Powered Location

Thank you for the replies.

I completly agree with you on the 40watt panel however that is just temporary, since the 80watt panel had some issues and i'm waiting for the 135watt panel to come in today to install it. So lets completly ignore that for now.

Both the 200amp batteries are setup to create a total of 400amp.

When i get this 135watt panel, how many more batteries would i need to be able to sustain a possible 1-3month situation with no sun(light outside just no direct sunlight). would 4x 200amp do it with the 135wat panel or would i posisble need more batteries or would it be possible to buy a higher wattage panel that can make up for the non direct sunlight situation???

the cable run from what i've tested i'm losing almost nothing, i've tested each panel on a 3ft cable for power 1st and then tested on the 75ft cable run and theres like no loss. accoridng to the morning star.

I was just giving a basic layout of my setup thats why i included that.

Cariboocoot · June 2011

Re: Remote Powered Location

Adding more batteries will only exacerbate the problem.

400 Amp hours of battery is going to require about 800 Watts of array. A single 135 Watts panel will do practically nothing towards recharging these batteries.

135 Watts @ 77% efficiency (typical) = 104 Watts / 14.4 Volts charging = 7 Amps of peak charge current. That's 1.75% of the battery capacity. About enough to stay ahead of the self-discharge rate, not enough to make up for any loads. In terms of "harvest" the panel might make 416 Watt hours - well below your expected usage.

Setting up a battery bank for months of use without recharging isn't practical. The self-discharge of standard batteries is too high; they'd go dead on their own without any use. Switching to AGM's would give you a break there, but certainly not months worth with draw. And the size array you'd need to recharge once the sun did come out would be tremendous.

It would be best to try and get some figure for the limited light you will get. One good thing about cloudy/foggy days is that you tend to get consistent light for longer time with less peak output. In other words the panels may produce only 50% of their maximum, but they will do it for six hours instead of just a couple hours in the middle of the day. (The diffused light gives a more even power output over a longer time.)

I'd suggest you set the battery bank at 160 - 200 Amp hours. If your usage needs are as I estimated in the previous post (480 Watt hours per day, requiring an 80 Amp hour battery at least) and size the array larger than necessary (perhaps even double) that is probably your best bet. Panels can be had anywhere up to 250 Watts these days, although they can be unwieldy, odd Voltage, and expensive. Some panel choices: http://www.solar-electric.com/hiposopa.html

You can put multiple panels on a system. Considering you're looking at over 400 Watts you should think about switching to an MPPT type charge controller too, as it will offer some power advantage and allow you to run more panel options such as higher Voltage strings which will reduce V-drop over that 75'.

Valus · June 2011

Re: Remote Powered Location

I'm abit confused. BEcaus ei'm currently only drawing 1.9 and if this system creates 7.0 thats providing enough for the equipment and the rest for the batteries to be recharged over time.

At that point once the batteries get charged it just a matter of sustaining the batteries when not bieng charged from the loss they will incur at night.

the point of having more batteries is to nomalize the loss of amp per battery while not being charged. i'm not relying on them soley to try and survive 1-3 months of not being charged. i'm trying to minimize the amount of contstant gain loss gain loss with the batteries.

However thats why i keep saying no direct sunlight but still light out. caus ethe panels will still draw power just probbaly half or up to 25%. this is why i need the info to create a system that can function.

ggunn · June 2011

Re: Remote Powered Location

Valus wrote: »

So awhile back I setup a Remote Location with some wireless monitoring equipment with a Panel and related equipment.

However my needs have changed as far as power consumption. i'm now pulling more power then the panels are producing and i'm losing power at this location at times.

At 1st i bought 1 40watt panel with 2x 79amp batteries and a morning star pro 30, which i then upgrade to a 80watt panel with 2x Deka 200amp batteries(all 12volt bateries).

(However the 80watt panel had some issues just in the last few weeks which i ha dto pull and temporarly put the 4owatt bakc on it.)

I'm now realizing again roughly 2 years later i'm running into the same issue not enough power(due to equipment upgrades). SO i went ahead an purchased a 135watt panel.

Now i had a custom box made to put all the batteries/invertor and the morning star unit.

However i need to prepare for winter time and roughly up to a month to 3 months of fog where i live.

i'm currently pulling almost 20watts load(1.9amps accoring to the morning star and currently only producing 1.7amps with current 40watt panel).

now my question is since i'm not good with the math and i sum how fudged it up twice. Exactly how many batteries would i need to be able to sustain say 1-3months of fog(still light out just no direct sunlight). I can currently put 4x Deka 200amp 12v batterie sin this box stacked. but i'm guessing that wouldn't be enough.

Look at it this way: Every bit of energy you use comes from the solar array; the batteries just store it until you need it. If you are falling behind your usage with your production and you can't cut your usage, then you have to boost your production, i.e., add more solar modules. More batteries won't help you. More batteries may hurt you, as a matter of fact, if your array is undersized to charge what you have now. At some point your array won't even be able to keep up with the batteries' self discharge, let alone power any loads.

Cariboocoot · June 2011

Re: Remote Powered Location

Attempting to "recharged over time" is what kills batteries prematurely. They like to be recharged today, right now, as quickly as possible. Not over the course of the week for use next weekend. 7 Amps of current is so far off the needs of a 400 Amp hour battery bank to get the electrolyte remixed and prevent sulphation that it is almost no charge at all.

Solar panels put out their maximum power in strong, direct sunlight. They will put out their Voc under almost any light. Put a load on and suddenly that drops. This is why we talk about hours of "equivalent good sun". Usually you can count on 4 per day, in most places. It varies greatly depending on location.

If you do not have an alternate charge source such as a generator for use when the sun hides behind the weather, you have to have a lot of panel to charge the batteries. Your loads may be only drawing 1.9 Amps, but if that is over 24 hours that's 45.6 Amp hours. Meanwhile you have 7 Amps for 4 hours, a total of 28 Amp hours, trying to "replace" the used capacity. This adds up to: "doesn't get fully recharged, ever". And batteries are not that efficient; they require more power to recharge than you can get back out of them afterward.

So you end up being at the mercy of the unpredictable weather; trying to second-guess how long you'll have to go before that direct sunlight returns.

Valus · June 2011

Re: Remote Powered Location

Okay this is what make sthings more confusing, and I think your all missing the point.

And whats worse is what yoru telling me is inaccurate to what i've been experincing okay. let me clear some things up.

i'll start from the beging since i think people are confuse dand missing my point.

Setup:
I originaly bought 1x morning star pro 30, 2x Deka 79amp batteries and 1x 40watt solar panel. This system workd fine until I increased the load.

I figured worng for the load increase so i needed to upgrade solar equipment.
i did this twice, thats why i had to upgrade twise as far as solar panels and batteries.

I then upgraded to a 80watt panel and to 2x Deka 200amp batteries for the extra load, this system also worked fine until the 80watt had an issue.

I then replaced the 80watt with the 40watt for less then a week. when i was again upgrading the load, i wan't aware of the panel having an issue until i wnet to do the upgrade so this is why i bought the new one.

I bought a new 135watt to replace the bad 80watt unit where as i had to use them temp 40 in the mean time.

Future
Now for future proofing. I need to make sure When fog season come sthis new steup will work.

so currently with a 1.9amp load i figured the 7amp solar would work plus having 2 more additional batteries will help make it so the batterie swill drain less because they are splitting the load.

What your saying:
however what i'm gathering from you is that adding 2 more batteries will take longer to charge and not actually do anything but hurt the situation which seems ass backwards to me, if you have 4 fully charged batteries vs 2 when night/fog comes you have more head room but your saying it's better to have less headroom/batteries.

On top of that your saying i'm not producing enough energy and that i need a higher rated panel. one to produce at least probably 50+amps. thats kool then if your saying i need to get a bigger panel or more somehwat of a problme though is i am limted to space.(but this is helpfull)

So what i'm also gathering is don't use more and higher rated bateries but get higher rated panel to keep battery full but when night/fog come they batterie swill die out due to not having enough total overal amps and not getting enough charge????

your contradicting yourselves.

now back on to the main point, WHAT CAN I DO TO GET THIS TO WHERE I CAN LAST UP TO 1-3MONTHS WITHOUT THE SYSTEM FAILING?????

I am limited by space, and i'm tgrying to not spend a fortune.

what would you do or buy to build a system that could last between 1-3 months of fog, limited by space and no option for an external power suplly without buying a $30,000+ generator.

i'm a nub remember thats why i'm here trying to get insight.

i'm asking because i need your opinions on what you would do what i could do not whats completly wrong with the current setup i know things are not gonna work. i just can';t do the math to figure out what i will need.

Cariboocoot · June 2011

Re: Remote Powered Location

Let's nail this down.

This load of 1.9 Amps @ 12 Volts: that goes on for 24 hours a day? If it does, the situation is just as I described: you have 24 hours of load @ 1.9 Amps = 45.6 Amp hours per day. You do not have 24 hours of charging with any solar panel; they only produce when the sun shines.

Take one 200 Amp hour battery. Run the load on it. Without any recharging the battery is dead in three days tops. Put 7 Amps back in to it for 4 hours per day and you're replacing about 60% of the power used. Battery doesn't go dead in three days, but will go dead nonetheless. If it lasts longer than 6 days I'd suspect the load is not what it appears or you're getting more sun than average.

You can not offset chronic undercharging by simply adding more battery capacity; you just delay the point of inevitable battery death. You must have sufficient panel to provide the whole day's worth of power usage in the short window of opportunity that the sun shines. There's no way around that.

Even "replacing the Amp hours over time" doesn't work, because if the batteries do not get sufficient charge current they will sulphate and die prematurely. This is a process where the plates become coated with the sulphor from the electrolyte - it acts as insulation on the plates and effectively reduces the real capacity of the battery. It will appear to recharge, but its true capacity is diminished.

Like I said before: get the battery capacity where it meets the daily power consumption (you have to include the time factor in the loads) and increase the panel capacity to the point where that battery can be recharged daily. If fog is going to be a problem then the array needs to be increased even more so the battery will properly recharge with whatever power is available.

There's no way around it. Bigger battery banks require more panel, and the minimum charge rate with no loads is 5% of the total Amp hour capacity if you want the batteries to last. Proper charging can keep those batteries going for ten years; how long did your previous ones last?

mike95490 · June 2011

Re: Remote Powered Location

Gasp - 3 months of Fog ?

This may be a rare case, where amorphous/thin film panels may work better in the diffuse light. They won't last 20 years, but in 10 years, there may be a better product.

Without direct sunlight, PV panels do not put out much power. On a moderate cloudy day, I get about 10% of my PV output. If it's raining, I get nothing.

So, you will need to go way oversize on your panels to keep your batteries alive.
Is there any way to conserve power, put your load on a timer, is it used 2am - 6am ??

BB. · June 2011

Re: Remote Powered Location

I think there is a bit of confusion about what each person is talking about...

First, the batteries. Typical Lead Acid batteries tend to sulfate (lead sulfate crystals grow) when a battery is below ~75% state of charge (25% of charge used). The longer the battery sits, and the lower the state of charge, the more sulfates crystallize. Once crystallized, that form of lead sulfate is an insulator and never "participates" in the battery charging/discharging cycles again... Effectively reducing the storage capacity of the battery.

So--what people are trying to say is that even if you had enough battery capacity for several months of no-sun operation, the batteries will be depleted (capacity wise) and even when you recharge them back to 100% State of Charge (SOC), the battery bank will never be the same.

Which is one reason why people here tend to recommend against adding more and more batteries to a system--because of sulfation issues.

Another issue, with standard flooded cell batteries, is (especially for "Tall" batteries) they "like" a minimum amount of current for mixing the electrolyte. That typically ranges from 5% to 10%+ rate of charge (i.e., 200 AH battery bank * 5% = 10 amps minimum rate of charge). For very large industrial cells (such as forklift/traction cells), 10% is probably the minimum rate of charge.

Another reason for the 5% minimum rate of charge is self discharge... For AGM batteries, as they age, you may get down to 1-2% self discharge per week... Not a large number.

For a large industrial flooded cell, you may get down to ~1-2% rate of self discharge in a day--a 5% rate of charge (~6 hours a day worth of sun light) vs 1-2% over 24 hours of self discharge--And your panels are struggling to just keep up with the loads.

Which gets back to your needs. It is probably financially and physically impossible for you to install enough AGM batteries to support your loads and not drop below 75% state of charge during that time period:

2 amps * 12 volts (I think) * 24 hours per day * 30 days per month * 2 months = 34,520 AH

Without knowing where the location is and how much "sun" you get during bad weather--it is guessing... But, if you assume a 1 hour of sun per day (0.62 derating based on 0.77 panel+charger derating * 0.80 battery efficiency):

2 amps * 24 hours * 14.5 volts charging * 1/1 hour of sun * 1/0.62 system derating = 1,122 watts of solar panel

Or about 1/2 that if you assume 2 hours of sun per day.

A "large" battery bank for normal off grid would be 3 days of "no-sun" and 50% maximum discharge for long life:

2 amps * 24 hours * 3 days * 1/0.50 max discharge * 1/14.5 volts = 288 AH battery bank

If you can use a backup genset, one option may be to find a propane powered generator from an RV wreckers (with electric start). That might be a good way to last through extended periods of fog/bad weather.

A lot of the previous discussion was centered around how to preserve your battery bank (i.e., have it last 5-10+ years, and not sulfate in two or less).

Depending on your needs--perhaps you can justify recycling the batteries early.

I guess it depends on how critical it is to have uninterrupted power 1-3 months at a time and if you can go there to manual recharge with a genset during bad weather...

The problem with solar arrays is they only work well in direct/full sun... If you have periods of poor weather--you can loose quite a bit of output. In my case, with a 3,500 watt GT system that can collect >20,000 WH on a nice day, I can collect <1,000 WH during stormy weather (5% of sunny capability). With light cloud cover--I probably get 30-50% of rated power in a day.

-Bill

rgk1 · June 2011

Re: Remote Powered Location

I am very new to solar also, but this is what I see as the direct answer to your question. Unfortunatly is all in the math

1.9 amps x 24 hrs = 45.6 amp hours required per day.
45.6 amp hours x 90 days no sun = 4,104 amp hours of battery
4104/200 amp hour Deka battery = 21 batteries (rounded up)
At that point they will be completely dead and most likely only partially recover when charging begins.

Now, what everone is telling you is:

4104 amp hour/7amps from a panel = 586.29 Hours of FULL sun to recharge the batteries.

586.29/4 FULL hours of sun per day = 146.58 days with NO OTHER power being used from the batteries during that 146 days.

This is assuming PERFECT conditions the entire time.

bmet · June 2011

Re: Remote Powered Location

It is hard to wrap one's arms around solar. Your loads dictate the priority. You say you have 7 Amps of Current , but that is for only 4 hours a day while the sun is nearly aligned with your panel. On the other hand, you are drawing a constant load of approx. 2 Amps per hour. Do the math.

4 hrs * 7 A = 28 watt hours

24 hrs (day) * 2 A = 48 watt hours

Your are slowly losing by a 2:1 margin, chronically undercharging your battery.

At full capacity your 200AH will run that load for:

200 AH / 2 A = 100 hours, but you never want to run your battery down completely.
Stay with 50% max discharge, and then your looking at two days of power without a recharge

Your load is constant, your Solar charge is not. This is why you will be running a deficit, and is why you have received the advice above.

Valus · June 2011

Re: Remote Powered Location

Holy crap, this is frustrating.

lemma try and brake this down becaus epeople are getting to technical and making things more complicated then what it needs to be.

okay
Assuming i have the 135watt unit nin play

135watt unit, at 7 load amps from 9am till about 6pm(your assuming i'm only getting 4 hours), witha draw of 1.9amps, unit stays charged during the day and only pulls from batteries at night.

Now lets say fog comes during the day i'll get roughly 25%-50% of that, so that would leave me at between 2.5-3.5amp, still enough to charge the battery and enought for the device. Now it normaly only takes 1 day to charge the batteries at 7amps and i've alsi been able to charge the batteries with that ratio in the past in 1 day and at lower amps.

even with fog i still create a solar loa djust not much. only time i'm not creating is at night and during a rain. we really don't get much rain. and we have a foggy season, which can be anywhere from 15days tyo 3 months non stop but still sunlight.

so again confusion one of the problems is yoru all basing your info on specific stats so tahts not going to work it would be helpfull if any of you actually asked quetsions instead of assuming my answers.

so far it seems like i'm wasting my time since everyone just wnats to give me the same answeres instead.

i think most of you are to concern with trying to keep the bateries fullycharged 24/7 which isn't possilbe and at a rate whihc is impracticle cost wise.

what i need is enought battert reserve to last thru the night and maybe a few days of no sun like a rainy time. and get me enough to where even with the fog i'm still pulling a load and still charge the batteries to a point where when night time comes they are good. but all i'm getting is no your not cretaing enough your cant rely 100% on your batteries when i've not once stated any of that. can you people please read my post instead of assuming what you think i'm trying to do i'm being pretty straight forward.

it's like you tell someone pick up the cup, yet they somehow think way beyond it's meaning.

edit Last 3 post dind't show up until o poste dmine i'll be reaidng thsoe in a second

Cariboocoot · June 2011

Re: Remote Powered Location

Never mind the fog, the panel, or whatever you had before.

All off-grid systems are based on load requirements.

If your load is 1.9 Amps average/steady for 24 hours on a 12 Volt system you need to supply 45.6 Amp hours @ 12 Volts.

Is this 1.9 Amps for 24 hours figure for the load requirement correct?

mike95490 · June 2011

Re: Remote Powered Location

The instant bright, direct sunlight is not present, power harvest falls off quickly, MUCH quicker than you are thinking.

If you have any readings of what your system measures harvest at on a foggy day (Amps harvested, for n Hours, measured, not guessed) we can use that to fine tune caculations for you.

You have had a low harvest problem for some time, we're just telling you the power facts also agree, the batteries will die from lack of recharge. You need a lot more solar.

BB. · June 2011

Re: Remote Powered Location

Lets assume that you have weather conditions similar to Fresno CA. Assume 0.61 derating (battery losses, derating of solar panels and charge controller losses); assume fixed array. And 1kW (1,000 Watts) of solar array (smallest PV Watts will accept):

"Station Identification"
"City:","Fresno"
"State:","California"
"Lat (deg N):", 36.77
"Long (deg W):", 119.72
"Elev (m): ", 100
"PV System Specifications"
"DC Rating:"," 1.0 kW"
"DC to AC Derate Factor:"," 0.610"
"AC Rating:"," 0.6 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 36.8"
"Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:","12.5 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 3.01, 53, 6.62
2, 4.55, 73, 9.12
3, 5.85, 102, 12.75
4, 6.78, 113, 14.12
5, 7.04, 117, 14.62
6, 7.20, 112, 14.00
7, 7.37, 116, 14.50
8, 7.47, 117, 14.62
9, 6.91, 108, 13.50
10, 6.11, 103, 12.88
11, 4.45, 75, 9.38
12, 2.79, 50, 6.25
"Year", 5.80, 1139, 142.38

PV Watts is based on ~20 year average measured solar conditions... Short term averages can vary +/- 20% over a month or year time frame (weather, other conditions).

So, for December, 1kW of panels gives about 50kW of useful power to your loads, or:

50,000 WH / 30 days per month = 1,667 Watt*Hours per day (December avg) for 1,000 Watts of panels

For 135 watts of panels:

1,667 WH * 135W/1,000W of panels = 225 WH per day (avg December)
225 WH / 12 volts = 18.75 AH per day

Your loads are ~1.9 AH * 24 hours per day = 45.6 AH per day load

From PV Watts (pick the "hourly output function), here is a "Bad Sun" day (426 WH per bad day per 1kW of solar panel):

1968, 12, 14, 07:00, 0
1968, 12, 14, 08:00, 0
1968, 12, 14, 09:00, 2
1968, 12, 14, 10:00, 12
1968, 12, 14, 11:00, 71
1968, 12, 14, 12:00, 138
1968, 12, 14, 13:00, 46
1968, 12, 14, 14:00, 92
1968, 12, 14, 15:00, 53
1968, 12, 14, 16:00, 12
1968, 12, 14, 17:00, 0
1968, 12, 14, 18:00, 0

And here is a "Good Sun" day from December (2,143 WH per good day per 1kW of panels):

1968, 12, 30, 08:00, 0
1968, 12, 30, 09:00, 5
1968, 12, 30, 10:00, 30
1968, 12, 30, 11:00, 335
1968, 12, 30, 12:00, 399
1968, 12, 30, 13:00, 456
1968, 12, 30, 14:00, 419
1968, 12, 30, 15:00, 283
1968, 12, 30, 16:00, 205
1968, 12, 30, 17:00, 11
1968, 12, 30, 18:00, 0

So, you can easily collect more power per good day (2,143 wh vs 1,667 WH average) or collect less (426 WH vs 1,667 WH on bad day--both based on 1,000 watt array) in December worst month of average power generation...

And compare to a typical August day:

1985, 8, 15, 06:00, 0
1985, 8, 15, 07:00, 10
1985, 8, 15, 08:00, 164
1985, 8, 15, 09:00, 300
1985, 8, 15, 10:00, 405
1985, 8, 15, 11:00, 496
1985, 8, 15, 12:00, 509
1985, 8, 15, 13:00, 511
1985, 8, 15, 14:00, 483
1985, 8, 15, 15:00, 424
1985, 8, 15, 16:00, 293
1985, 8, 15, 17:00, 166
1985, 8, 15, 18:00, 15
1985, 8, 15, 19:00, 0

The 9am to 6pm is only possible during the middle of summer... During winter, your generation is significantly less (with fixed array).

Your system may be a bit small to justify a Battery Monitor (such as a Trimetric)... But perhaps a DC AH/Watt Hour meter ($60) may be worth while for you to totalize your daily load and daily power generation.

I understand your frustration--but I am still having problems trying to figure out how to answer your questions.

During Summer, you have lots of sun available (say >7 hours of full noon time sun equivalent per day). A 135 Watt panel will output:

7 hours of sun * 135 watts * 0.61 derating * 1/14.5 volts = 39.8 AH per day (long term average)

Still a bit less than the 45.6 AH per day you are using... But--again these are averages, so some days your charging will exceed usage, and other days may not quite.

-Bill

bmet · June 2011

Re: Remote Powered Location

Valus wrote: »

135watt unit, at 7 load amps from 9am till about 6pm(your assuming i'm only getting 4 hours), witha draw of 1.9amps, unit stays charged during the day and only pulls from batteries at night.

Have I misunderstood your load this entire time? Do you mean that in a 24-hour day, your equipment is only drawing a total of 1.9 Amps? OR do you mean that your equipment draws 1.9 Amps every hour? Which is it, because that would make a huge difference in the number of batteries you need.

The panel you purchased is a great panel, but it can't do the impossible. A photovoltaic panel only produces it's maximum current when the sun is near the correct position in relation to the direction the panel is facing. For most locations in the continental United States that yearly average is about 4 hours per day.

You wont be getting 7 amps from 9 am to 6 pm (unless you are running a tracker). It'll be from 10 am - 2 pm, or noon - 4 pm, or whenever the sun is directly over your panel's Local Vertical, + or - 10 degrees.

Plus, the Imp rating on the back of the panel is derived from a static test that is never duplicated in real life. Most likely you may only get 80% of 7 amps.

This isn't to say you won't get a good output from your panel during the rest of the day, it just won't be 7 Amps, probably not 6 Amps either, more likely it'll be half the name plate rating, before and after those 4 good hours.

You seem to be fixated on an idea that more batteries is better, but without properly recharging them, you will be wasting your own resources, time, and productivity.

None of us want that to happen, and is why we are trying to understand your circumstance.

dwh · June 2011

Re: Remote Powered Location

Good batteries aren't cheap.
Draining a battery below 50% will shorten its life.
Draining it below 50% on a regular basis will shorten its life.
Failing to fully recharge it will shorten its life.
Failing to fully recharge it -in a timely fashion- will shorten its life.
Leaving a battery partially charged for months will shorten its life. A LOT.

If you build a system that does not take good care of the batteries - then you better plan on buying new batteries every couple of years.
If you don't spend enough on solar to take care of the batteries, then you WILL spend more on batteries.
Your choice.

Solar panels don't really work very well.
They put out less power when they are hot.
They are dark colored and pointed at the sun, so they are often hot.
They don't do a good job of harvesting unless there is enough light.
They need GOOD DIRECT sunlight to get a good harvest.
There are usually only a few hours a day when the sun is hitting the solar panels just right to give them enough light to harvest.

On days when there is not GOOD DIRECT sunlight - you might get some harvest, you might get nothing.
You cannot plan on that. You *think* you might get 25%. Maybe - maybe not.
You might get 3% today and 1% tomorrow and 30% the next day. HOW CAN YOU PREDICT?
You can't.
So you plan on nothing and do the math that way.

Setting up a solar system that *works properly* IS technical.
You cannot do it properly without doing the math.
If you won't do the math, or listen to those who are doing the math FOR YOU, then all you can do is HOPE that it works.

The information you have given is VAGUE.

EXACTLY how much wattage does your station consume per day?

1-3 months? Which is it - 1 month or 3? Obviously, 3 months requires a system 3 TIMES LARGER than 1 month.

9am-6pm? Not a chance. ONLY if you use a tracker to keep the solar panel pointed at the sun all day.

The people here will help you - they help everyone who asks for help.
They have a lot of practice, because a lot of people ask for help.
They will do the math for you if you can't or won't.
They will try to save you from shooting your own foot off.

But they can only help if you give them GOOD NUMBERS to work with.

There is NO MAGIC. There is NO MYSTERY.
There is THE MATH.

And one more thing...

3' of wire vs. 75' of wire and no difference?

No. Your experiment has a flaw...

The problem with longer wire is "voltage drop".
Voltage drop increases with LOAD.

If your battery is already charged - the charge controller is pulling almost nothing from the solar panels and the load on the wire is almost nothing.

So the voltage drop is almost nothing because there is no load on the wire - and you will see no difference between 3' of wire or 75' of wire.

BUT...

When the battery is low and the sun is bright, the charge controller will be pulling full power from the solar panels - the LOAD on the wire increases - so the voltage drop increases.

THAT is when you'll see the difference between 3' of wire and 75' of wire.

bmet · June 2011

Re: Remote Powered Location

Your last point cleared up a question I had. Thanks.

techntrek · June 2011

Re: Remote Powered Location

To clarify, the things said near the top of the post 2 posts ago applies to lead acid batteries, there are other less-used battery chemistries that don't need to be fully charged or charged at all to prevent damage. They can have other benefits like lighter weight, increased performance vs. lead acid in colder temperatures, etc. But they are rarely used due to cost.

dwh · June 2011

Re: Remote Powered Location

techntrek wrote: »

To clarify, the things said near the top of the post 2 posts ago applies to lead acid batteries, there are other less-used battery chemistries that don't need to be fully charged or charged at all to prevent damage. They can have other benefits like lighter weight, increased performance vs. lead acid in colder temperatures, etc. But they are rarely used due to cost.

The OP specified Deka in his first post.

ggunn · June 2011

Re: Remote Powered Location

Valus wrote: »

Holy crap, this is frustrating.

lemma try and brake this down becaus epeople are getting to technical and making things more complicated then what it needs to be.

It's not us; this stuff is by its nature complex and technical. Balancing power requirements, battery capacity, and solar generation on an off grid system, even a small one, is a non-trivial task. You can do your homework and find a solution that will work for you, or you can cobble a bunch of gear together and hope it works. It's your choice, but if you do the latter your chances of success are not very good.

Seven · June 2011

Re: Remote Powered Location

Valus wrote: »

Holy crap, this is frustrating.

135watt unit, at 7 load amps from 9am till about 6pm(your assuming i'm only getting 4 hours), witha draw of 1.9amps, unit stays charged during the day and only pulls from batteries at night.
How many hours are you drawing 1.9 amps? A 1.9a load for two hours is a total draw of 3.8.
so far it seems like i'm wasting my time since everyone just wnats to give me the same answeres instead.
The guys here are giving the correct answers with the info you have given.
It is hard to find better info than you will get here.
i think most of you are to concern with trying to keep the bateries fullycharged 24/7 which isn't possilbe and at a rate whihc is impracticle cost wise.
Not fully charged, just not below 50% charged.

edit Last 3 post dind't show up until o poste dmine i'll be reaidng thsoe in a second

The people here will spend a good amount of time to answer your questions. The answers provided may not make you happy, but I have found in my limited time here, that they are usually spot on.

techntrek · June 2011

Re: Remote Powered Location

dwh wrote: »

The OP specified Deka in his first post.

He also mentioned buying more batteries in the first post, so I wanted him to know there were more options than just lead acid.

ggunn · June 2011

Re: Remote Powered Location

techntrek wrote: »

He also mentioned buying more batteries in the first post, so I wanted him to know there were more options than just lead acid.

True, but other battery technologies are far and away more expensive, not mixable with his existing batteries, and (as we have pointed out) merely adding batteries to his system will not solve his problem.

Remote Powered Location

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