OFF GRID POWER; various thoughts on...

[Headed for the Hills]

OK, have been struggling with my solar power.  I have seven (7) 15 watt Northern Tool panels connected in parrallel and connected to a Sunforce 30 amp charge controller.  However, even under the best lighting conditions I have only been able to produce .6 amps and usually only .2 amps to charge my battery bank (running a 12 volt system).  Have used the connectors provided when I wired the system, but am wondering if I should cut the connectors off and use wire nuts to connect the wires or even soldering all the wires.  No addditional wire has been added, so I don't think power is lost in the wire length.  Shouldn't I be producing much more than that?  Any help would be appreciated.

[MountainDon]

Nice looking installation tickhill.



Forklift batteries. My own opinion is that if you have a forklift go ahead. At 115 lbs apiece a Trojan L16 is already heavy enough.


My dream battery bank would be 12 Surette/Rolls S-1380 2 volt cells in series. More capacity than we now have; probably want some more panels too and then we could use an electric fridge most likely and save propane.

[MountainDon]

7 x 15 = 105 watts,   divided by 12 volts = 8.75 theoretical amperes at panel rated output.  

How are you measuring that amperage? Test meter wired into one of the wires between panels and battery, like in the + lead. Are the batteries fully charged when metering the charge rate? If they are full then the charge controller is doing its job and keeping the current to a float rate.

I have 1  1/2 of those panels hooked to the RV batteries to maintain their charge over the winter. (1  1/2 as one panel is cracked and the output has fallen   )  It's been a while since I metered them as the batteries stay up fine. But IIRC on a sunny day I was getting about one ampere from the one good, unbroken panel.

So with them all parallel connected you should be getting much more than the 0.2 to 0.6 amperes. Either the panels are not putting out or there is excessive resistance somewhere. With loses like that I would expect to find a warm to hot connection someplace (full sun and battery needing to be charged).

Wire nuts are a poor idea for DC circuits. If it was me I'd cut the leads so they are only a bit longer than required. Leave some extra length in case you have to reconfigure them someday. With a good terminal lug crimped or soldered on each lead you could make up your own combiner with some strap copper, a drill, S/S bolts, washers and nuts (in a weatherproof plastic box). Crimp connections are fine; better in those cases where joints end up being poorly soldered. Connect the charge controller to the bus bars with adequately sized wire. With each panel wired to a bus bar like that it is easy to remove a panel at any time if needed. Plus you would have less resistance with shorter leads and better connections.

Have you tried metering the output from each panel separately?

[Headed for the Hills]

Thanks for the reply.  I'm measuring the amps thru the charge controller.  Checked each panel with volt meter during install and all read between 12 and 14 volts (didn't check amp reading though thinking back, probably should have).  The connectors provided were plugs and with either cigarette lighter ends or just bare leads.  Took the ones with the bare leads and crimped them all together.  Plugged the panels in and ran wiring to the charge controller.  Checked voltage at charge controller and got the same reading as directly from the panels.  Purhaps a charge controller issue?

Do you think creating the bus bars inside a weather proof box would work better? 

Also, can you separate panels to where half are in the sun during the morning and the other half during the afternnon?  Or would you lose power to those panels not charging while the others were?

[MountainDon]

If your panels are like the ones I have on the RV they came with a "trailer light" connector, into which you can plug the 'extension' with the bare leads or the cigarette lighter plug. I would cut those connectors off. Before doing that I would carefully mark the positive and/or the negative leads.  I use white tape on negative wires. Any system you can remember works.

If you have all the positive leads (7) connected together and then all 7 negative leads connected together (parallel connections) and measure the voltage in bright sunlight you should have something like 18 volts, maybe more with nothing at all connected to the panel outputs. This would be the same as the output from one panel.

With the charge controller input connected to the panel outputs and the charge controller output connected to a partially charged battery, in bright sunlight, you should likely see something like 13.5 to 14.something volts at the battery. Measure the amperage in either the positive or the negative lead from the charge controller to the battery. That will be the current the charge controller is passing to the battery. The battery needs to be partially discharged in order for this to be accurate. Theoretically the charge current could be up to 8.75 amperes, but most likely your real world result will be a little less.



As for half the panels facing one direction and half another direction, everything in parallel, and feeding through the same charge controller I'm not certain on the outcome. I think that should be okay with the equipment you have. I'm not convinced that will result in any better total power output for the day if the weather/sun conditions were the same all day.     You could improve the output of the set that was directed for best AM power but at the reduction of the power from the ones that were directed for PM output. With everything pointed the same direction, most likely south, I believe it will all average out, given the same weather/sun conditions.

[Windpower]

Thanks for the temperature info, Don


I am thinking the 'pump house' is going to be a perfect location for the batteries and inverter and charge contoller

[Headed for the Hills]

Thanks for the input Don.  Next time I go to the Cabin, I think I will try and re-wire using your suggestion.  I was suspect of the "plug-in" connectors and had thought about wiring differently from the start.  I am new to solar power (as you can tell), but am eager to have an operational system and staying off the grid.  Nothing major, just lights and a ceiling fan.  At the most, 3 or 4 CFL's and a small fan.

My panels are wired to a small battery bank (2-35 amp hour batteries) and then to a small inverter.  Doing my rough calculations, the 7 panels should easily keep the batteries charged.

Am open to an suggestions and will post later with more questions I'm sure.

[MountainDon]

With a small system like yours a fan that runs right off the batteries might be nice. DC lights too so you save the inverter loss. As much as I like my own inverter powered system, for something very small I would think about strictly DC.  Just a thought. You can get DC powered CFL lights with the screw in edison base if you do not like the type of light LED's put out, or their cost.

[MountainDon]

Here's some info from the Trojan battery company. This may be specific to their batteries, or in other words, if you have some other brand of batteries this data may not be what the other guys recommend. This data is also for flooded lead-acid batteries, not any type of sealed or non lead-acid battery.




http://www.trojanbattery.com/BatteryMaintenance/Charging.aspx

[glenn kangiser]

The Morningstar takes the L16's a bit higher to 32v on their special L16 battery setting which agrees with my experimental findings and info I  rec'd from an knowledgeable solar dealer in Lake Powell area.

[MountainDon]

A question regarding Equalization was asked in another topic. I thought it might be best to copy it to here and respond here as well...

Flooded lead-acid batteries, imperfect things that they are, will develop inequalities between cells over a period of time. They may start out with more or less the same specific gravity (state of charge) but this may wander over time. The goal of equalization is to eliminate these variances between cells. This is done by applying a higher voltage than what is normally used, and at a low charge current. Equalization charges will cause excess gassing to take place, therefore the fluid levels must be watched. Equalization voltages also causes the "stirring up" of the electrolyte. Tall batteries may be more affected by stratification than shorter batteries. The rapid bubbling mixes things up.

Equalizing produces large quantities of hydrogen and oxygen. Good ventilation under equalization is necessary. I open the battery enclosure doors and leave them open.



Regular battery charging has three stages. All good battery charging equipment will have the basic three, Bulk, Absorb and Float. A better or best charger will also have the equalization capability. Whereas the bulk, absorb, float charges are programmed in and will automatically progress as the battery charge builds (in the best units they are user programmable), the equalization charge is usually initiated manually.

In the bulk stage, current is sent to batteries at the maximum safe rate they will accept until voltage rises to near (80-90%) full charge level.

In the second stage, absorb charge, voltage remains constant and current gradually tapers off as internal resistance increases during charging. It is during this stage that the charger puts out maximum voltage.

The third stage is float. After batteries reach full charge in absorb, the charging voltage is reduced to a lower level to reduce gassing and prolong battery life.

If battery power is being consumed during the charging the charger can shift back and forth between stages as needed.


Equalization should only be necessary a couple times a year. Too frequent use of the equalization cycle could reduce battery life. If the specific gravity readings show irregularities with increasing frequency that may be a sign of a batteries impending demise. Glenn had had some good fortune with desulfating processes.

Here's another chart with slightly different values....



That one is from TheSolar.biz  http://www.thesolar.biz/Battery_charging_article.htm

[MountainDon]

It probably can not be stressed too much that equalizing applies to flooded lead-acid batteries. AGM and gel cells are not the same. Flooded lead-acid means the type of battery with removable caps, ones you can add water to.  Other battery types can be damaged.

[glenn kangiser]

Also, mentioned before but again....Keep water levels above the plates during equalizing or permanent damage may result.

[diyfrank]

Got it, Thanks 

[Tickhill]

Glenn, got the other 3- 190's yesterday and hope to get them online this weekend. Will probably add another set of batteries also. Then it is time to bury conduit and run the power to the barn. Dad and I will probably wait for some rain to soften up the ground.

[Dave Sparks]

Don and others!  here is a link from a ways back where folks at the outback forum were trying to use energy wasted after the battery was mostly charged offgrid. They basically are heating water with a coil. It does work but I have always thought it was a big time waster as it is so much more efficient to use the sun to heat water directly. It is far better to use an electric heat pump for excess energy.  It might give you some insight on your experiment Don. Let me know and I can get you a model number for and SCR.

http://outbackpower.com/forum/viewtopic.php?f=29&t=2865&hilit=electron&start=25

[MountainDon]

Thanks Dave.

Well.... I haven't posted the reason for what Dave just referred to before this. Here goes as succinctly as I can.

The PV panels don't need to do much when we are not at the cabin as there is no electricity used for anything. The PV system simply has to keep the batteries at full charge. So there is "wasted" power. Anyone with a PV system hates to waste a single watt, let alone a whole days worth.

What to do with the excess power?  Heat something comes to mind.

One of the drawbacks to a cabin in the boonies is that during freezing weather, December to April, more or less, water freezes. Dry/dried foods such as beans, pasta, rice, flour, etc. goes only so far. You can only eat so much peanut butter. Frozen glass jars (spaghetti sauce) break. Metal cans (beans, meats, fish, veggies, fruit) may have seams crack and spoilage set in when it warms. Freeze dried food varies from so-so to okay in my opinion, with okay being a euphemism for "at least I won't starve to death as long as I have this."

So it occurred to me that possibly there was sufficient excess PV produced power to use with a resistance heater, in conjunction with an insulated box to provide a storage space that would remain above freezing.

I asked Dave if he could recommend a solid state relay to use with the diversion capability of the FlexMax charge controller. That would allow the excess power to be used for heat after the battery state of charge was assured to be full each day.

Obtaining an appropriate SSR is no problem. PV cells are the real problem. PV cells are still grossly inefficient.  

I have collected weather data, including solar watts per square meter. Winter sun angles sure kill what's hitting the panels. I've run my figures a few times over a long period of time. Without getting into the actual numbers let's just say that maybe IF we had three to four times the number of PV panels, then maybe we'd have enough excess PV power to heat a small food storage locker. A well insulated locker with lots of mass to help make it through the night.

This needs some more thought. As Dave has suggested, it may be much more advantageous to use a solar water heater and storage tank with a small solar driven pump. The collector could be set up as a drain back type and used antifreeze as the liquid. More of the suns energy would be used. The downside, in my case, is the solar situation at the cabin is poor. That actually depends on the season. It's actually great having all the shade in the summer.

With some more thought this could be used to provide warm/hot water for domestic use. (In the winter we usually do not even use the water heater as the water system is left drained for freeze prevention. In summer this could save a little propane, not that we use a lot for water heating.)

If anyone wants to get into my numbers, calculations and theorizing, just say so.

Thoughts, comments, arguments, encouragement, discouragement, etc. all welcomed.  
Spin off to a cold weather food storage topic?  Or leave it here are it is related to Off Grid Power? Or perhaps an Off Grid, non electric power topic?

[Bob S.]

Don: Do you think some sort of root cellar would work?

[Tickhill]

Got the extra panels up, here is a picture. Will post kwH sometime tomorrow. We went from around 19 amps charging to 35 as soon as I brought the panels online.

[MountainDon]

Don: Do you think some sort of root cellar would work?

I'm sure that would work. I simply don't want to dig a big hole and all the rest that would be required. It would have the advantage of being a place I could leave some potatoes, carrots, but considering that it is just to allow us to go up there for maybe a total of 20 nights from mid December thru March I'm not sure that's what I want to do. I may change my mind over time. Thanks for taking the time to respond.

I/we did more thinking about this while we were at the cabin the past couple of days. Some more thoughts, ideas and questions to come. Likely in a new topic.

[Bob S.]

I think you could keep a root cellar from freezing inside with a light bulb.

[MountainDon]

I think you could keep a root cellar from freezing inside with a light bulb.

There are many places where that could be a solution. However, resistance electrical heating can be too big of a drain on small off grid systems. Thanks though.

[glenn kangiser]

A new off grid problem and solution.

DSL modems seem to be highly susceptible to power surges and resets as loads change on inverters.  Nearly every pump start our DSL resets and then it is 2 minutes more to stabilize.  A real pain when posting on the forum.

Apparently it is a common problem in countries without stable power.  I often wondered but found the answer on a forum from Pakistan.  The tech there said that the DSL modems were not made to handle the instabilities in inverter power.  He recommended a UPS.  Before that I was not sure if they smoothed out the surges or not.  They do as the tech said.

A good quality UPS (un-interruptible power supply) takes whatever power there is available and smooths it down sending out stable power to the battery and surge protected outlets.  I got one from Amazon and it arrived today.  I have been running today through multiple pumping cycles without one interruption.  Hooray.

This is the one I got  - it was the most value and biggest for the money as well as being a good brand and having high recommendations - note that there are some that others would never buy again.  Read the reviews before you buy anything.

http://www.amazon.com/APC-Back-UPS-Outlet-550VA-120V/dp/B0019804U8/ref=pd_ys_iyr1


I did read of one person trying to stabilize a cheaper UPS as he had problems with it, but good ones are pretty cheap and take care of the problem.

[glenn kangiser]

Today - second day of the UPS -

I can hear it switch over to battery (relays click) as the pump starts cause system surges.  No internet DSL loss.  It just happened.

[MountainDon]

That's cool!  Another use for the old UPS we don't need.