Ken Hall's posts

You need a lot more than a diode.

Depending exactly where you are, you can expect about 2 hours of full sun at this time of year. That is about 600 watthours of solar generation a day. (it will jump to about 1300 watthours in the summer)

You did not say what your loads are, but my guess is that your electrical usage probably exceeds the 600 watt hours a day, probably by quite a margin.

You are trying to fill 7920 watt hours worth of  batteries with about 600 watt hours.
When you discharge that bank more than 7.5 percent, you just don’t have the generation to fill it.

I could be wrong, but without any load data, I think you just don’t have enough solar panels (especially for this time of year).

Ken

The best place to get code advice is from your city (or county) building permit office. Codes can vary all over the place.

For grid tie solar systems the local utility may also have requirements that must be met. Today, many of the building permit offices are aware of those, but sometimes they refer you to the utility.

Your connection at the main box will require dedicated backfeed breakers. Many jurisdictions will consider that sufficient. In addition to the breakers, some jurisdictions will require a seperate disconnect. And, some of those will require that the disconnect be lockable.

Ken

James

The ABYC is the American Boat & Yacht Council

Among other things, They develope consensus safety standards for the design, construction, equipage, maintenance, and repair of small craft.

Their standards are really good ideas, but the statement that they "mandate negative ground systems" is an over statement. They have no legal position to mandate anything.

The real mandates are

The United States Coast Guard. Title 33, CFR 183 which contains mandatory requirements for electrical systems on boats.

NFPA 302, Fire Protection Standard for Pleasure and Commercial Motor Craft. This standard is approved by the American National Standards Institute and is applicable to motorboat installations.

That being said, I think that there are some real safety issues with mixing the two different polarity systems on a boat, or in an RV. Sooner or later someone, somewhere, will inadvertantly cross the systems.

Ken

Steven:

You should probably start with the "how-to" tab at the top of the page. Then click "the basics". Within the list that comes up, you can select "electricity basics".

There is a lot of good info located under the "how-to" tab, but many people seem unaware of it.

Ken

Steven:

I haven't used the battbak charger, so I can just make some educated guesses based on info I've seen on the internet.

I suspect that using the larger panel is not going to improve the 7 hours of charging time, which I assume is 7 full sun hours. I think the charger is only going to accept the charge at about 250mA per cell in the charger. Excess power will just drive the panel voltage up a bit.
What the extra power will do, is prevent the charge time from extending due to dust on the panel, an overcast, etc.

The 24 hour limit in the charger is for AC charging. Leaving the cells in too long on trickle charge can heat damage them. On solar power, you would have leave them in several days to accumulate that amount of time and they will have a chance to cool down overnight. so it shouldn't be a problem. I would still attempt to unplug the panel within a reasonable time period of the charging being complete, but I would not not worry about them.

The controller will be of more use with the 12V system.

Ken

Steven:

What type of loads are you going to have on your 12V battery(s)?

A 5W panel is best for maintaining a charge, offsetting the self discharge. It can replace very small draws. But it will only give you about 13 amphours a week, under the best conditions. At this time of year, it will be less. Maybe 8-9 amphours, depending where you live.

If you use the panel for 7 hours of full sun charging AA batteries (2-3 days), that does not leave a bunch of power for the 12V system. Maybe 5 amphours.

Ken

Scott:
A DC disconnect and the appropriate sized fuse out by the array is a good idea and in many areas would be required by code.

Different Inverters have advantages. But all I can guess is that you are thinking about a grid only type installation.

You need to describe what you wish to build, features you must have/would like in the system, the size of the PV array, a generic description of the layout, geographic location, future expansion if any is forseen, etc. An idea of the budget.  The more details you can provide, the better the recommendations can be.

Ken

What is the AA battery charging problem?

Camera shops sell battery chargers (generally for AA Nickel Metal Hydride batteries) that come with both 110v and 12v dc power supply cords. The 12vdc has a cigarette lighter type connector.

So, other than a charger/battery type incompatability,(eg attempting to charge ni-cads in a NIMH charger) I don't see what the problem is.

Ken

Robert:
Here is a link that will explain panel shading.
http://howto.altenergystore.com/The-Basics/Solar-Electric-Panels-Overview/a36/p2/

I do not generally worry about one panel being more shade tolerant than another. I take the attitude that shading is bad for all panels and think you should do everything possible to avoid it. As an example, if shading one cell results in a 50% drop in production with one panel, and another panel has a 45% reduction, do you worry about the 5% difference? Or do you say that I am going to avoid the drop, period, whether it is 45% or 50%. I treat periods of partial shade as zero panel output, and then am pleasantly surprised if I actually got something.

I tend to take the same approach to panel aiming. The variance between panels is usually less important than your location (Lattitude/hours full sun). At 38 degrees North (San Francisco Bay), laying a panel flat would cost you about 15% of the panels production on an annual basis. So, having a fixed tilt would save that loss. Being off 45 degrees from true south would result in about a 10% loss, annually. (Note, these figures would vary for a person that would only use their boat for the summer months.)

If the panel mounting is adjustable for both tilt and azimuth, you can actually pickup similar percentages. AS an example, aiming a panel with a fixed tilt, SE in the morning, S midday, and SW in the afternoon, might pickup about 10% over a fixed south panel. And, if you are laying around the boat in an anchorage, it is not that hard to adjust a couple of times of day. Similarly, being able to adjust tilt late in the afternoon can capture a few more watts, if you pull into an anchorage later in the day.

Ken

"Then the cable can be modest (AWG 6-8) still with minimal losses."

If you define minimal losses to be 2% voltage drop, you can only push about 173 watts on 8 AWG for the 200 feet (48V).

With any substantial amount of power, he is going to be on a larger wire size, probably in the 1/0 to 4/0 range.

Still waiting to hear more details from the OP. First solution I would look at is moving the inverter.  Many people think it has to be close to the main panel. Does the OP just believe that, or does he have a real reason for it ?

Another interesting wrinkle.

If the system was recently installed and received a govermental rebate, tax credit, or utility rebate when installed, would any of those entities want a refund if you un-install it ?

On most boats, the negative ground 12V system and the bonding system (designed to prevent electrolysis) meet at the engine block. If I was attempting to tie a positive ground system in, I would want a disconnect in the negative from the battery to the engine. I would not want the  positive potential on the bonding system.

The wiring problems would also be exacerbated by the presence of a shore power charger (hard wired) or an onboard generator.

I haven't thought all the potential problems and interfaces though. It could be done, particularly for a boat with a simple system. But I think I would just ask James to recommend a negative gound controller, and eliminate the headaches.

Ken

John:

It is unfortunate that you did not get a warning about your turbines. The Whisper 200 is built to maximize the power at low-moderate windspeeds. Once a site hits an average annual windspeed of 12 mph or more, I think the Whisper 100 would be a better selection.

It sounds like your site has a higher annual wind speed. I would guess 15-18, from the sounds of it. I would recommend that you stop the cycle. Sell those turbines to someone who needs a low-moderate wind machine.

Buy new turbines that are more suited to the higher wind conditions of your site.

The other possibility is to talk to the guys at southwest windpower about the problem and what are the REAL differences between the two machines. The one that I am aware of is the prop. It is possible that just down sizing the prop to a 100 prop MIGHT resolve a lot of the problems. 

Ken

Mike:

Marine environments vary, so it depends how harsh it is. The cold clammy salt fog of the pacific northwest is pretty brutal on them.

In any particular marine climate, having the inverter sit powered down for a good part of the year, will allow more condensation etc. than if it were powered up.

The question will become one of do you spring the extra bucks for a marine inverter or do you just go ahead and use a standard one, knowing it will have a shorter life span. The answer to that depends a lot on the size of the inverter and what features you want in one. Marine inverters are aimed at the boating market.

Regardless of what inverter you decide on, I would give some consideration to making the installation with the provision for quick removal. If it is going to sit unused, why not have it sit at home in the garage. Safer from the environment and better protected against theft.

Ken

John

Actually, I am trying to get his attention and get him to slow down. He's jumping around like a cat on a hot tin roof.

The other approach he can take is go minimal, 12v lights only, and possibly a small inverter load in the summer when he has more power availible. (An inverter that can be disconnected so there is no parasite load when not needed.)

Realize that the system will not be expandible. Use it as a learning experiance. Make the mistakes on a small cheap system.

Then come expansion time, make the decision whether to transfer the lighting loads onto the new system and sell/toss the old, or keep it and have two systems.

Ken

Michael:

You are about to make a $1500-$2000 mistake that we have been trying to warn you about.

That cabin kit you are looking at is really more suited to stick in a RV trailer.

I told you “You need to get some hard numbers on the fridge and how many hours a day it runs. It will drive your system size.”

John told you “Decide (ie measure) how much power you need, and then decide”

James told you “then get a kill-a-watt and measure the heck out of what you would like to run.”

We know that the loads and reserve factor drive your battery size. The 2 in combination, plus the solar insolation for your area,  drive the size and number of panels. It is harder to design a small system than a big one. A small mistake that would pass un-noticed in a large system, will kill a small one. There is just less room for errors. And we are already know the answers and are making allowances for things that you have not even thought about yet.

I would bet that if you ask James why AE doesn’t sell kits, he will give you an answer something like “kits really don’t work very well, each customer has different ideas and desires, we would rather customize the system for each of our customers needs and circumstances.”   

In about a year, you are going to crying that the controller you bought is noisy, doesn’t really seem to fill the batteries as rapidly as other controllers. That it doesn’t talk to other equipment that you want in the system, and you seem stuck at the 2 panel size. The system is not delivering more than 600 wattshours with the 2 panels at this time of year etc. (meaning you will only get about 300 watthours a day with one panel)
And possibly you will be complaining about the AGM battery , if that’s what you are thinking of buying.
The battery is not in the kit, nor is an inverter.

So, go right ahead and spend that $1500-2000 bucks, it’s your money.
Enjoy the period of euphoria that you will have right after you install it, because that happy feeling isn’t going to last very long.

Ken

Michael:

Don’t make the mistake of thinking small is energy efficient. Some of those 2 cu ft fridges are monster power draws for their size. You can often get an energy star rated fridge in the 14-18 cubic foot range that will run on the same power, sometimes even less.

John is right about doing more reading, you might try the “how to” tab at the top of the page. There are some good articles and some helpful calculators.

In your first post, you said that you want to convert to solar.  If you are currently on grid and using it similar to what you plan to in the future, knowing the KWH off of a recent months bill would help.

Ken

Michael:

You need to get some hard numbers on the fridge and how many hours a day it runs. It will drive your system size. I would actually recommend that you get a kill-a-watt meter (about $30) and plug the fridge into it, so you can get a real good number on what it uses at this time of year.

If your desire is to have it plugged in 24/7/365 and be able to power it plus the lights in Dec/Jan, I believe this system is bigger than you think.

"I would go up to about 500.00 if needed."

You are probably looking at something closer to 10 times that amount, and possibly more, depending on the numbers.

Ken

Lawrence:

Jim is correct that you can take the numbers too seriously, especially the momentary ones. The battery monitor is the best solution. But if you are not ready for one yet, there are other ways.

The simplified voltage method is OK, but the fine print on it says that there should be no charging or discharging for two hours before taking the readings. Particularly if your battery has been charging (or a high discharge rate), the readings can be thrown way off, if taken too soon.

Most systems have either an amp meter(bi-directional) or a watt meter in them. If not, you can add one, or use a clamp-on.

Make a simple table for the C rates showing both amps and watts for your battery. For a 200 ah 12V battery, C5 is 40amps or 480 watts. C10 is 20 amps or 240 watts, etc.  Put this Table with a copy of the curves from the article, near your system. 

You walk in and determine whether the system is charging or discharging. Read the watts or amps, (and the voltage) and look up the C-rate on the table. Then on the appropriate set of curves (charging or discharging), follow the appropriate C-rate curve to determine the state of charge by the voltage reading.  If your amp or watt reading is in between the C-10 and C-20 rate, just do a little interpolation between the two curves. After you have done it a couple of times, the whole process takes maybe 30 seconds.

To work around a low load, say C100, you can wire up a 100 watt bulb as a test load. (Larger systems, just use more light bulbs) If you come in with a 2 amp (24 watt load) on the system, flip the switch and add the 100 watts to it. Give it a few minutes, and then take your readings. In this example, you will be almost exactly on the C20 curve (for a 200ah battery).

Your objective is to know that you are somewhere around 90% or 95% state of charge. Trying to figure out “I am exactly at 92 percent” is beyond the accuracy of the method, any way.

You could also go to hygrometer readings. Temperature corrected, they are more accurate than voltage readings.  However they are sometimes messy, and take a little more time.

Many of the people that talk about state of charge (SOC) have some sort of state of charge meter or battery monitoring system. Some of these are as simple as the manual method outlined above, others use more complex algorithms and/or other sensor inputs, such as battery temp. Simple SOC meters used to start at about $50 and very complex monitoring systems can run well above $500.

If you are handy with a soldering iron, Richard Perez did an article for Homepower that had a design and parts list for a SOC meter that could be built for about $10 (early 90’s prices). 

Large systems with consistent loads and generation that operate in the 80% plus range are easy to build, particularly on an unlimited budget. Smaller systems, with inconsistent loads or generation (or both), will take larger swings in their state of charge.

And finally, some of the people who maintain that their system “stays above 80 percent” just don’t monitor it often enough, to see the swings happen.

Ken

Here is a good article for you on detirming state of charge with a voltmeter.
www.homepower.com/files/battvoltandsoc.pdf

The answer is that your battery is about 10 percent discharged.
It can be detiremined by the resting voltage, or the voltage underload.
The 16.67 amp load on the 200 amphour battery would totally discharge the battery in about 12 hours. This is known as a C12 discharge rate.  If you use the chart on page 3 (also labled 68 at bottom of page) and follow the C10 curve, the 12.4 volts also indicates about a 10 percent state of discharge.

Victor:
One more series of questions. Is that really a 48v DC generator ? Does it have any provision for 115V or 230v AC output ? Does it possibly generate an AC voltage that is then rectified to DC ?
Ken

Victor
Eric's advise is extremely bad advise, that risks severe damage to the equipment.

I don't know exactly how your unit is wired, but I believe that the DIP switches are there so the manufacturer can sell one cabinet with one set of controls and put either a 24V or a 48V unit in it. An owner could also replace the 48 with a 24 or vis versa.

The actual generators are normally a hard wired unit and the voltages cannot be changed just by flipping switches.

Hopefully, the controls are sophisticated enough to sense the problem prevent the start. Or cause an immediate shut down. If they are not, I hope no one is standing close to it.

I've still thinking about your problem. If you could describe the system config a little more, it might help.  How big is your battery bank and do you have plans to expand the storage if you change voltages ? How many watts of solar panels do you have ?  How well balanced are your loads to your current generation and are the loads going to increase ? I am under the impression that the windmills are not yet installed. Correct me if I'm wrong on that. What to you expect as far as power from the windmills ?
Ken

Ken

"Can anyone give me a valid technical reason why it won't work."

What do you mean by it ? 

If you mean connecting the chargers in series, you run a risk of the control circuits not working properly. The batteries may not charge at all. You could also end up with uneven charging of the batteries, or frying the batteries. There is also a good risk of pushing to much amperage through the control circuits, which could fry your chargers. There are a lot of different logic circuits used in battery chargers, different ones will react differently.

If you meant splitting the batteries, the risk is that if the two chargers charge at slightly different rates, you end up with the batteries eqaulizing the charge between them, the first time you put a load on them. This gives you a high discharge rate (and an energy loss). Repeated cycles of this higher than normal discharge rate shortens battery life.

If you are careful to charge the batteries as evenly as possible, this shortening of life may be minor. But as an example, suppose you only get 54 months instead of 60 months of life out of them. Is it worth the risk ? 
As long as your willing to accept the risk, and live with the no loads during charging, there is no technical reason to prevent it.

I think if it were my system, I would spring for the 24V charger. But, if I was trying to get by with the two 12 volts, I would probably install a knife switch in the series connection.   

I don't know of anyway to do it automatically.

If you are manually charging the batteries, you can kill all the loads, break the series connection between the batteries, charge what are now two 12 volt batteries, and the re-establish the series connection after charging is complete.

This should be an "emergency" type practice rather than a regular thing. Your battery life is better if you charge the whole bank as one unit rather than as two seperate units.

Dimensions and weight are also key specifications when dealing with forklift batteries.

They are big, and they are HEAVY. The 48V 500AH battery you mentioned is going to weigh about a ton, and possibly 2500 lbs, depending on mfg. and model. Many of them are one piece and do not break down.

If it turns out to be some thing much smaller, then you could consider it.

But unless you are going to dramatically increase your electrical loads, you would be far better off buying say 2 t105s and a single 12v panel. It will cost you less than half of what the 4 panels to make the 48v would cost.

Ken

Max:

The first thing I would suggest is to read the basics/beginners guide to solar located in the how-to-section, if you haven’t already done so. Here is a direct link to it.
http://howto.altenergystore.com/The-Basics/Beginners-Guide-to-Solar-and-Wind-Generated-Electricity/a19/

One of the links within it, will be to a load calculation sheet. Print it out and use it.
After you determine what loads you are going to have on the system (in watt hours) as daily loads with no one there, daily loads when occupied, and then the emergency refridgerator load, will then be able to size your battery bank. 

After you finalize the size of the battery bank, then you can size the solar panels accordingly.

Your comment about getting the batteries from work, scares me. I looked at the Interstate deep cycle flooded battery line and did not see a 232 AH battery there.  If they are not a deep cycle, you do not want to use them for solar service, even if you get them cheap.

I do not like to plan on cycling a deep cycle battery below 50 percent, except on a rare  emergency basis. Your two new 232 AH batteries will only have 232ah total, when wired as 12v. They will only provide 116AH under my 50 percent criteria. 116 AH (at 12v) is 1392wh, so it will give you less than 3 hours of heater time assuming that the heater is running at the 500 w setting.  Depending on the wattage of your lights, you may be down to only a couple of hours.  Or looking at it another way, if you fully load that 1250 watt inverter, you will only have an hour and 7 minutes of running time.

So, I believe that even your new battery bank will be undersized. You have been getting away the loads on your current batteries, because of the trickle charger where you are filling the batteries 24/7. When you go to solar only, all the power comes in during the day. There is no new power until tomorrow. 

There is a device called a kill-a-watt meter that you can use to measure the electrical consumption of your heater or fridge to get a handle on typical daily usage. Some people have difficulty estimating how much they actually run.  It retails at about $35 and can be found for less.

Ken

Do you realize that the largest of those converters would only handle about 13 percent of the generators output ?

If you are going to play with converting electricity, you need to think of generation and loads in watts, not amps. Amps are best used for wire and fuse sizing. If a load is listed in amperage, convert it to watts. Voltage times amperage, equals wattage.

If you have two 6 volt 10 watt panels, wiring them in parallel will give 20 watts at 6 volt.  Wiring them in series will give 10 watts at 12 volts.

If you need the amperage, divide the watts by the volts.  The parallel panels would be 20 watts divided by 6 volts, equals 3.33 amps. The series panels would be 10 watts divided by 12 volts, equals 0.83 amps.

You might think about telling us what you have and what you are trying to do. If, for example, you have a couple of 6 V 150 microamp panels (0.9 watts) and you are trying to tie them together to charge a 12v car battery, that would be a waste of time and money.

The battery is a goner, and needs to be replaced. But before you install it, I would ask a few questions.

The first one is what is the last thing he did to the charging system and when ?

The most likely way for a battery to reverse polarity is to have someone cross-connect a charger (without polarity protection) to it when it is in a low charge condition. If he had a dead battery and charged it, that is probably your answer.

If he did anything else to the charging system recently, he may have reversed connections somewhere, which could also cause the reverse polarity of the entire charging system.

I have also heard of a few cases in certain rectifying schemes where a part (diode?) burns out and reverses the polarity.

So, it would probably be a good idea to check the polarity of the charging system immediately upon initial start-up.

The starter failure does not surprise me, particularly if it is an auto start generator. Once the start circuit called for a start, the starter motor would run backwards with the reversed polarity and the bendix would never engage. The starter motor would just keep running backwards until it fried.

Victor:

Most of the propane refriderators and freezers have a natural gas conversion or burner kit available. On this site, most of them will be listed below the unit in the add ons/options area. If you do not see anything there, try clicking on the blue + sign.

Price of the kit varies, but genreally in the 50-75 range depending on MFG.

Ken