John D's posts

With that many batteries, I would connect each of them to a positive and a negative bus bar.  Then run wires from each of the bus bars to the inverter. 

The bus bars I use are actually grounding bars for circuit breaker boxes.  I got them for about $5 each from a hardware store.

Keep all wires as short as possible, and use heavy guage wire.

If you still want to connect the inverter directly to the batteries though, you should connect the plus wire to battery 1, and the negative wire to battery 12. Then each battery has the same amount of jumpers between it and the inverter. Draw this out if you're not sure what I'm talking about. 

John
 

In other words you'll need two of them, one for each function.  Still, that's a lot of technology for not a lot of money.

It looks as if the x1500 is nothing more than batteries, an inverter, and a battery charger. Unless I missed something you will need a charge controller.  Given the size of the solar panel you've selected, you could get by with a charge controller that costs as little as $50.00. Look at some of the low-end Morningstar PWM ones. 

You might also consider building your own PV system from scratch.  You could then choose batteries and an inverter that more closely meet your needs, and that better match the size of the solar panel you've selected.  You should then end up with a more efficient system, and one that is expandable. 

John

I misread your post, thinking that you said it is a long run of wire to the mystery fixture.  You can troubleshoot by:

1. trying a known-good bulb in the mystery fixture. 
2. checking with a voltmeter as I previously said.

You might also look for bad connections, or maybe a bad switch or fixture.  Your digital voltmeter is your best friend. The key is to see if there is a significant voltage drop across the wiring.  Then you might check for a bad switch.  A voltage drop across the switch, when the switch is turned on, indicates a bad switch. 

john

 

If you need to go back to using an inverter, try to eliminate waste by:

Choosing an efficient inverter.
Operating the inverter close to it's capacity.
Choosing an inverter that goes into standby or power-saving mode when there is no load.

John

The long wiring run seems to be the problem.  Your losses when trying to run 12VDC a long way are greater than they are when you try to run 120vac the same distance.  An easy test would be to measure the voltage across the light bulb at the distant fixture with the light turned on.  You might measure something like 9 volts, which means that 3 volts is lost in the wiring. 

John

How many hits do you get on your website each month?

Steve,

I would like to suggest that you connect all of your batteries to positive and negative bus-bars.  That way it will be easy to disconnect batteries one by one for testing and troubleshooting purposes.  I bought my bus-bars from my local hardware store.  They are actually the grounding bars that are used inside breaker boxes.

John

My first off-grid PV system started with about a dozen used UPS batteries.  It worked well for awhile.  As the batteries aged, and failed one by one, it was a hastle to sort out the good from the bad.  A couple of marine deep cycle batteries from Wal-Mart made life a lot simpler.

Also, it seems that you're planning to mix batteries of different capacities as well.  That is not recommended.  Still, if I were to start over again, I would probably do what you're planning to do. 

And since you're starting off small, I'm wondering why you've chosen a $129 charge controller when you could get by much cheaper.  I suppose it's because you want the display, right?  I decided to go with Morningstar, with display, and I love it.

I have a small-scale solar PV system that I hope to use someday to provide at least a portion of the electricity required to charge an electric car.  I might buy a "Th!nk City" car when they become available next year. I've written many articles about alternative transportation on my blog http://solarjohn.blogspot.com

I agree, there's nothing wrong with starting small.  High oil prices will be followed by high electricity prices.  That will trigger a big demand for solar panels, making them hard to get and more expensive.  Meanwhile, you'll be enjoying the benefits of free electricity while others are turning things off to cut costs.
 

As you do your research into solar and wind you'll find that you'll need to spend a lot of money for a relatively small amount of power.  You'll soon realize that conservation and efficiency improvements are a better use of your money.  Having done that, if you still want to invest in solar and wind, go for it.  However, unless your electricity rates are exceptionally high, don't argue with your dad about the financial benefits of alternative energy.     

To make a long story short, it's not practical to build a grid-tied system if you have only two PV panels.  You'll need permits, a grid-tie inverter, and the services of an electrician to hook things up.  This is a large expense for the small amount of power you would get from your system.  If you really want to build a small-scale PV system consider off-grid.  To answer your question;  you would use a transfer switch (automatic or manual) to connect your inverter to your house wiring. You should get an electrician to do the wiring, unless you have electrical wiring experience and are familiar with the electrical codes. 

Since you only have two panels, you might consider doing what I've done.  I didn't wire into my electrical panel.  I use an automatic transfer switch to control power to only two items, my refrigerator and freezer.  I've set it up to use batteries (through an inverter of course) as the primary source of power, and automatically switch to grid-supplied power when the batteries get weak.   

You're welcome, and thanks for the comments.

I have an electronics background, so I guess that's why I like getting into performance and optimization.  I suspect that you also have a technical background as well, am I right? 

I measure everything I can measure, and I even use a data logger for timed samples. I'll change some parameter, like the size of the load, and then repeat the test.  A test may run for a week, allowing me to consider how varying weather conditions affect the results.   

Be careful Michael, or you'll get addicted like me!  haha

sj
 

Yes, battery voltage does drop as the load increases, and that causes the charge controller to provide more current (if possible).  The charge controller seems to do what it does based on battery voltage. 

When battery charging progresses through the "absorption" stage, the % of charge (amount of charge current) gradually declines as batteries become nearer to fully-charged. 

A small increase in the size of the load will cause the % of charge to increase.  A large increase in the size of the load will cause the controller to go back into the "bulk" charge mode. 

With my system, the charge controller and the inverter do not communicate with each other.  I have, however, added automation to switch my inverter on and off based on battery voltage, but that is a topic for a whole different conversation. 

In General:  The charge controller efficiently charges the batteries, while protecting the batteries from overcharging.  My added automation protects the batteries from over-discharging.

I've explained in detail how my system works on my blog:  http://solarjohn.blogspot.com

It is interesting to watch the meter on the charge controller as the loads change.  I've noticed that my batteries charge up pretty quickly on a sunny day, and the inverter goes to the "absorption" charging stage.  For example:  In the absorption stage the meter might indicate that charging is taking place at 20% of full capacity.  While my PV panels are capable of providing 25 amps to the load, panel current drops to 5 amps (as an example).  Then, the compressor on my refrigerator kicks in.  The load goes from 15 watts to 200 watts.  The charge controller quickly goes back to "Bulk" mode, providing as much current to the load and batteries as the PV panels are capable of producing. 

There are only a few possible scenarios, and it seems that the charge controller handles all of these in the most efficient manner possible.  The charge controller seems to power the load as the top priority.  Often, power from the panels can power the load, while still providing some power for battery charging at the same time.

On a cloudy day, with the inverter powering a load, you can watch the system go through all of the possible scenarios.  At one moment the power to the inverter load might be coming from the solar panels.  Then, a cloud passes over and the load is powered by batteries.  Often, the PV panels provide only a portion of the power needed by the load, and the rest comes from the batteries. 

I hope this answers your questions.
   

That is a GREAT inverter, I love mine, but I bought it new and on sale for less than $600.00.

Matching the PV array to the (size of) the battery bank is an important consideration.  Too small of a PV array might result in chronic under-charging, shortining the life of the batteries. An excessively large PV array, with respect to the size of the battery bank, might be a waste of money.  (I'm looking for a way to burn-off excessive energy during the day, after my batteries are fully charged). 

After determining the appropriate battery bank size, selecting the type of batteries is an important consideration. AGM's are great for many solar applications, but one charging/discharging mistake might ruin an expensive battery set.  Ordinary lead-acid batteries are a little more forgiving, and less expensive.   
 

I agree with the others.  Installing at least a small system will give you a feeling of freedom from the electric grid with its high costs.  My modest off-grid system meets only about 10% of my electricity needs, but it has served me well during power outages.  I've also learned a lot about conservation, and with everything I've done, I've cut my electric usage in half over the past two years.

You might be better off with an Iota DLS-series battery charger.  Be sure to get the IQ-4 option.  These are three stage (bulk, absorption, and float) chargers.  I understand that you can leave them connected and power applied.  To protect your batteries, and to avoid wasting power, this seems like a much better option than to use timers.

 

Measuring current is not as easy as measuring voltage because current flows through a circuit, while voltage is measured across a voltage source or a component.  If you get a good quality digital voltmeter, and a precision resistor, you'll get fairly accurate results.  I'm not sure about the accuracy of other types of devices mentioned here.  But on the other hand, being able to measure watt-hours is a good feature, and something you'll probably want eventually.

You'll need a shunt and a digital voltmeter.  A shunt is simply a precision, low-resistance, high power resistor. You'll use ohms law to determine current and power.  Let's say that you have a 0.01 ohm resistor rated at 100 watts. If you want to know how much power your batteries are delivering, put the resistor in series with your batteries.  Let's say, that with a load attached, you measure 0.3 volts across the resistor.  Apply ohms law:  I = e/r.  I = 0.3/0.01 = 30 amps.  Next measure the voltage across the load.  It will be about 12 volts.  Since current flow is the same in all parts of a series circuit, you have 30 amps at 12 volts across the load.  Apply ohms law again.  This time:  P = EI.  P = 12 times 30 = 360 watts. 

You can put the shunt resistor in series with the PV panels to determine their output in the same way.  So there you go, a low-cost substitute for a TriMetric.  You should be able to buy a shunt from the alt energy store, or else an electronics outlet such as www.digikey.com. 
 

Both the 300-watt inverer and the 2500-watt inverter can be powered by the same battery bank, and turned on at the same time, but their (AC) outputs cannot be physically wired together.  You can power some lights with one inverter, and some other load with the other inverter, at the same time.

Another thing to consider is efficiency.  Inverters tend to be most efficient when operating near their maximum capacity.  If you'll be powering a few lights and a radio most of the time, you would be better off using a 300-watt inverter.  You could switch on a 2500-watt inverter when you need the extra power.  You can use them both at the same time of course, but they're not stackable. 

John

Thomas and Robert have already provided some good advice, but I would just like to add this:

You may want to start with a pure sine wave inverter instead of the MSW inverter you have in mind.  I started with a MSW inverter and wish that I hadn't wasted the money.  Motors ran at the wrong speed, making my timers useless.  I had noise in the audio of my radio.  I had streaks in the TV picture. I was always worried that I would damage something, so I seldom used the inverter. 

You might want to start with a 300-watt sine wave inverter instead, as your loads are fairly light.  Later, when you upgrade to a more powerful sine wave inverter, you'll still want to use the 300-watt unit at times because that will be more efficient than to use a big inverter for a small load.

Just MHO.
John
 

I have no experience with the MC1 or MC2 connectors, so perhaps I shouldn't be responding, but I will anyway.  Having many years of experience as an electronics troubleshooter I know that connectors can develop resistance over time, especially those that are exposed to the elements.  It may not be noticible at low current, but will be more troublesome as current increases.  And, if you add an adaptor as you suggest, you're adding another set of connectors that could cause problems.  I prefer a good, tight connection inside a junction box,like you have in your Kyocera panels.  But again, those who have experience with connectors may have a different opinion. 

It sounds like you either have one or more bad batteries in your battery bank, you do not have enough PV capacity with respect to the size of the batteries, or you have a load that is keeping your batteries from getting fully charged.  It would help if you would tell us more about your system.  Adding lower voltage panels to your system does not seem like a good solution.

Travis,

I think it is also important to note those who are not entirely off-grid, but rely on alternatives for a portion of their electrical needs.  I have 425-watts of PV, and I use that to power my refrigerator and freezer.  I've automated my system so that it switches back to grid-supplied power when my batteries get low.  At the present time those devices run for about 12 hours per day on energy from the sun.  I add to the system as my budget allows, and may someday be able to go totally off-grid.

http://solarjohn.blogspot.com

John

I see no reason why you can't.  If one side of your roof has a southern exposure, your set.  I think you'll find the information here helpful:

http://solarjohn.blogspot.com/2007/02/mounting-solar-panels-on-your-roof.html

Good Luck!
John

Hi Jonathan;

I use a Morningstar Relay Driver, which is actually 4-voltage controlled switches.  I could have gotten by cheaper, but I wanted to be able to expand later.  The relay driver costs about $150.00.

The relay is nothing special.  For ease of hookup, choose one that has a coil rating that is the same as your battery bank, 12 volts dc for example.  You could even use a solid state relay if you so choose.  I use the relay contacts to turn on/off my inverter, so the relay doesn't need to pass a large amount of current.  In other words, the off/on relay does not pass the potentially high dc input current of the inverter.  (I hope you understand what I'm trying to say).

The automatic transfer switch is made by Iota.  It's rated at 30 amps, and it set me back about $55.00.  Actually, it's nothing more than a relay. 

My inverter has remote on/off capabilities, or in other words, a terminal block.  This terminal block allows me to wire in a remote on/off switch, or in my case, the relay contacts.

The lascar data loggers are programmed via a PC, and use the time/date information from the PC.  If you're setting up two of the lascar data loggers from the same PC, the time/date information for both of them should be farly close.  You'll set the sample intervals, (1 minute, 5 minutes, 30 minutes, etc.), and they should be fairly closely synchronized.  There is no way that I know of to actually connect the two data loggers together for exact synchronization, and there are no buttons or switches on the data loggers. 

John