In general, lowering an electronics product by 10 degrees doubles its life. Will an XW-4548 last as long as a XW-6048 in your application? no one can say for sure. Running the XW4548 at 90% will run hotter than a XW6048 will run at 70%, The larger unit has more FET's and larger transformer

I assumed with a 4500+ watt solar array that debating a cost increase of 700 dollars was a very small part of the overall cost of the installed system. Further, since you selecting an XW inverter with battery backup, you intend to run house loads if power is lost. a 6Kw inverter can be much more handy that the 4500 watt in this case and if the time comes you do use this configuration, when a load can't be added running on battery's your going to lick yourself for "saving" 700 dollars

This is all my view and I understand everyone else has there way of seeing things

I didn't know about the 10 degrees to double the lifespan. That really is gigantic.

Also, I do agree with going with the larger XW6048, but they are apparently not available to purchase at this time.

That's the guideline we use for spacecraft electronics too. (within reason)

Hot/Cold thermal cycles are a big factor too, heating parts up, and cooling them down, causes cracked solder joints, broken wires etc.

By the way, the 10 degrees is "10 Degrees Centigrade" not Fahrenheit (would be 18 degrees Fahrenheit). And the corollary is that you drop the temperature by 10 degrees Centigrade/Celsius, you will extend the life by 2x.

The other "killer" is thermal cycling... It is better to avoid cycling temperatures too, both min/max temperatures and temperature cycling (keep things between cool and warm vs cool and "hot" cycling, and try to reduce the numbers of thermal cycling). I used to evaluate disk and tape drives in another life and found (really confirmed) that thermal cycling and fast ramping (within product ratings) of environmental temperatures would kill any product that was not properly designed and assembled.

-Bill

OK, I've been wondering about this for days.

How do you know that the battery voltage would be ~ 51 volts DC? Is that because the battery bank should be 48V for maximum efficiency? And what if you use only 24 V? Are there benefits? From the Xantrex XW Calculator, it seems that 24 V would give me more options for the solar panels.

Well, maybe now after writing the questions I have partially figured it out. Is it 48V because that allows each XW-60-150 to deliver the maximum watts back to the grid? So if it was 24V you could only deliver half as many watts, and would need two inverters instead of one? But the charge controller could handle as much as 150V? But you really can't have a battery pack over 48V for safety reasons?

Thanks for the help.

The 51 volts comes from how the XW-6048 or FX-3048 ( outback ) sells to the grid with a battery based system. A Fully charged battery is 12.7V , so X4 = 50.8V . Anything above this then is going into the battery as excess charge ( with a fully charged battery bank )

The Charge Controllers will be current limited to what the inverter picks for a sell voltage, the more the chargers put into the battery, the more load the inverter apply s to the battery's. A voltage just above fully charged battery's means the excess charge is flowing into the grid, not the battery's.

To have the same wattage at 24V, you need 2X the amps so 2X the controllers. Also efficiency drops at the lower voltage as current losses are the Square of the current in electronics, so double the current and the losses increase by a factor of 4X. This is why high voltage gridtie units are so efficient, they are much lower currents and use the higher voltage to get the same wattage

Battery based systems are not over 48V ( nominal ) due to safety and regulatory concerns

As to why you don't want 150V into the charge controllers, since they are very high current units, there are other losses in these devices, one is called switching loses that increase as the voltage input increases and at 60 amps the loses really build up, which means more heat and lower efficiency in the conversion

Hope this helps!

YES, the replies have been very helpful. The problem is every time I learn a bit more I have more questions. I don't know why it has to be so complex.

OK, I understand the XW6048 is at 48V, selling to the grid. So therefore the battery pack MUST be 48V? I think so, but I'm not sure.

The charge controllers hook into the inverter, but I'm not sure how many controllers you can have on one inverter. I don't know if you also need a "distribution panel," which I don't know what that does.

Can the charge controller work on a different voltage than the inverter? I think it can, because they say the controller can even charge a battery pack with a higher voltage. But do you just set the voltage on the charge controller based on the PV panel setup you're plugging into it? And then the charge controller is set up to change the incoming voltage to 48dc outgoing since you've got an XW6048? And if you had an XW4024 the controller could and would be set up to change the outgoing voltage to 24dc? And if you had two charge controllers they could each work on a different incoming voltage depending on the PV panel setup for that controller, and each controller would change the outgoing voltage up or down to match the inverter it was hooked up to.

Somehow this must all make sense once you read the manuals and have the equipment, it is just so difficult to figure it out before so you know what equipment to get.

Thanks for the help.

Well it is complex and forums can help with some basic understanding, but your talking about a very lethal voltage/current/power setup and this is not a good first time project

I think what your missing is that the inverter / battery's have nothing to do with solar, its a device that takes energy from the battery's and makes 240 vac in the XW's case

Solar chargers take solar energy and charge battery's, the connection goto the battery's NOT the inverter and have there own breakers, combiners distribution panels ect

Now in what your considering, you will run this inverter so the excess charge into the battery ( can be from ANY source that is charging the battery's ) and have that sell back into you grid.

There is so much more than this basic understanding. You have NEC ( National Electric Codes ), this must be installed to these regulations and inspected by either polk-county building department or Bartow City building department in your case and they have an entire process to make sure you do it correctly. You have battery selection and sizing, all the required interconnects, breaker and or fusing, the wiring and sizing, conduit requirements. Choosing the preferred equipment is just a very small part of the process

If you should choose not to do the permitting process, you put at risk your home as it can't be sold ( permit for work will need to be shown at sale ) and if there is a claim on your home owner insurance, they will disallow any claim as you installed a power system without proper permits

I am happy you choose to visit and post at my forum and I and other can answer questions and help with learning about possible system choices, but don't fool yourself thinking we can provide an online course that will allow you to install a 6kw solar / hybrid / grid tie solar system. Unless you have the training or work with someone who does, you likely to have some dangerous results that can hurt you, your family our your property.

Yes, I agree completely. Even if I was crazy enough to try this at home, the state has saved me by requiring it to be installed by somebody who knows what they are doing.

However, sometimes those who "know what they're doing" only want to do it their way. That is why a forum such as this is so beneficial and appreciated. The answers are informative AND independent. Like the guy who was told to put the 3kw inverter on the 4.5kw system and nobody could figure out what was going wrong until this forum gave him the correct answers.

I am being told that it MUST be either 18 or 24 Sharp 224 panels, or the Xantrex XW6048 won't work properly and the warranty will be voided. That isn't what even the Xantrex website says. So it is very confusing.

From what I have learned here, the batteries are like a bathtub. The PV panels put energy (or water for this anology) in, going through the XW-60-150 charge controllers. It doesn't matter how much energy (water) is being supplied by each controller, they are independent. Then, when the inverter needs energy (water) for whatever reason, whether to power the house or sell to the grid, it is drawn from the battery bank (bathtub).

So the real question the becomes:

Why won't they let me have 22 Panels like I want, instead of either 18 or 24 panels, which I'm guessing is 6 or 8 strings of 3 PV panels hooked together?

The Xantrex website says it would be OK with 4 strings of 2 Sharp 224 PV panels for the controller, so if you have two controllers that would be 16 PV panels. Then, for the third controller there would be 3 strings of 2 Sharp 224 PV panels, that would be 6, for a total of 22 panels. I have also considered 3 strings of 3 Sharp 224 PV panels on two controllers, and 2 strings of 2 Sharp 224 PV panels on the third controller.

(A side story: When we were building the house we were told the warranty for the front door would be voided if we painted it the dark color we chose instead of white like the designer and builder wanted, because the door faced East! We said we didn't care, put it in writing and give us the color we chose. There was no further discussion, and AFAIK the door is still under the warranty.)

I don't know "who" is telling you 16 or 24 sharps, I don't even think sharps make sense, your much better off cost wise using Evergreen panels

The only install I know in this area is solarsource, they use beacon products, which I have explained to them are below the bottom of the barrel, they get a great deal on them, thats all they install or sell

It very simple, the panel increment is what ever it takes to have the solar panels output ( vmp ) be higher than the battery charging voltage. here in Florida you should chose either

( 5 ) 12V panels in series
( 4 ) 18V panels in series
( 3 ) 24V panels in series

for 48V batterys, you need at least 60 volts vmp, in the summer heat the panels will run about 70C

Use the Xantrex String calculator to verify the panel manufacture and exact panel and temperature range ( ambient ) min/max

Then you can put as many stings in parallel ( with fusing and combiners ) as the charge controller is rated for. When that is exceeded, just add more charge controllers

On the inverter / battery side you have two concerns. First is how long you expect to keep things powered off the battery's by themselves and second when running Gridtie only, the inverter still need a decent battery pack for technical reasons I'm not going into, but for an XW-6048, figure a MINIMUM of 440ah for a 5kw grid-tie operation ... which gives you about 10kwh of energy for when your running stand-alone down to 50% depth of discharge. We have here in Lakeland Battery US and I got my 220ah 6 Volt AGM's for about 5K ( 16 of them, 8 in series the the two strings in parrallel )

Here in Florida, I have yet to met an installer that has any technical depth in selecting manufactures or options for inverters , panels and battery's. They are so small ( volume ) they find a wholesaler to see a single brand of parts and that's all they do. You really can't expect much more, there just is no business to make this full time for them