XW+ 6848 - Does it require batteries? (yes)

[morgandc]

Does anyone know if the XW+ 6848 require batteries to run in grid tied/Sell mode? It would be nice to be able to install the panels, charge controllers and XW+, get a better idea on utilization before sizing/spending on the battery bank. The new shop/house will be a lifestyle change and I can't predict utilization.

-Dwight

PS Lets skip the hybrid being stupid discussion.

[morgandc]

I found a link to the install manual..... the answer appears to be yes.

Note: The minimum recommended battery bank is 440 Ah per inverter/charger.
The Conext XW+ Inverter/Charger is designed to operate with batteries and
should not be operated without them. Also, do not allow the battery bank to
become completely discharged. If the voltage of the battery bank falls below 10
volts, the Conext XW+ Inverter/Charger will not operate.

[ncs55]

absolutely correct.

[Mike90250]

Yes, it does require batteries, even for Grid modes.

[morgandc]

Have you seen any grid tie systems that can provide usable voltage during daylight hours when the grid is down without batteries? Run the pump, cool down the fridge, etc?

[Sunking]

Have you seen any grid tie systems that can provide usable voltage during daylight hours when the grid is down without batteries? Run the pump, cool down the fridge, etc?

No such animal of use exist. There are a couple of invertrs that provide a very small amount of power, but nothing significant or really usable. You are spinning your wheels looking for a ghost.

[morgandc]

So, would the right conclusion be that you have to use a power storage system or design the solar array for a single device (or multiple devices with a constant load) so that the load/voltage range stays in the proper limits? IE for a well pump, it is either running or off.

[Amy@altE]

You need to do a loads list. i.e.

Load Qty Watts Hours Surge On at once Watt hours

Pump 1 750W 2 hours 2250W Y 1500Wh
Lights 6 13W 4 hours 13W N 312Wh
---------------------------------------------------------------------------------
763W 2263W 1812Wh

Total the watt hours to size the array and batteries and total the amount of watts that will be on at once and the surge to size the inverter.

Google "Loads List Calculator" to help you.

[morgandc]

The direction I am thinking/wondering is how can you use solar panels without the grid or batteries? So, PV Direct. Without the batteries or grid to buffer between the solar panels and load you can't use your grid tie panels to power much. There is a product (American Gridtie Independence 4400) that will allow you to use you grid tie system during a power outage, but it is just using batteries again to buffer/balance the loads. And we know how expensive/short lived batteries are.

How can you buffer your solar panels to allow usage during daylight hours? There are a lot of things that you could do with that power during the daylight if you have a large system, but you can't really use it. So close, and yet so far.

[Amy@altE]

You can get a PV direct pump, and pump water to a tank while the sun shines. SunPumps, ShurFlo, and SunRotor all make Submersible solar pumps. The correct model depends on the head and flow required.

Other than that, any grid tied inverter required the grid to be functional to provide any meaningful power, although SMA can provide up to 1500W if the grid goes out, but that's not what you are asking for. Any off-grid inverter requires batteries. Solar panels do not provide enough consistent power to run loads that are not specifically designed to be run PV direct.

[morgandc]

Thanks, I found the right terms for the search engine...... amazing how many people what to run their panels without batteries. You would think there would be a few more commercially viable options. Perhaps the SMA inverter with the standby power supply is a sign of things to come.

[PVAndy]

No such animal of use exist. There are a couple of invertrs that provide a very small amount of power, but nothing significant or really usable. You are spinning your wheels looking for a ghost.

I suspect you referring to the Secure Power Supply feature on the SMA SunnyBoy xxxTL-US-22 inverters.

While you may consider 1500W max of 120 V small, they are capable of starting and running an Energy Star refrigerator. We have installed several hundred of them and tested them pretty extensively. SMA also runs a refrigerator constantly on one in their Denver lab.

You may find this video from SMA useful in seeing what one can run https://www.youtube.com/watch?v=Yb7KQDc2yqk

One trick that makes it even more useful is to run a high DC / AC ratio on the inverter so that you maintain adequate power to put out 1500 W during partial shading and early morning / late afternoon.

I'll be running 2 of them in my own house.

[morgandc]

I wish that SPS feature was automatic. So you could run that circuit directly to the freezer/refrigerator and get the benefit automatically...

[compchat]

I have two Sunnyboy US inverters. One is 6 KW and one is 5 KW. They both have the 1500watt emergency power when grid is down. I'm wondering.
1. How to connect the two 1500 watt supplies into one 3000 watt supply.
2. Possibly creating a subpanel with only the important circuits and connecting them to the 3000 watt max supply. Instead of running extension cords everywhere.
3. Backfeeding the 3000 watt supply into something like a dryer socket with the main power supply breaker off and only the breakers set on for this lights, tv, refrigerator you need to use. This would of course mean turning the main breaker off when using the system so as not to send power down the line to the electric company.
4. A more sophisticated and safe way of doing number 3 such as building a subpanel with breakers only for those circuits you wish to power. Anyone have a line diagram or equipment suggestion ?

Thanks

[ncs55]

I would not recommend that. I think the inverters will not sync up, you might call SMA to determine this.

[Ben25]

I wish that SPS feature was automatic. So you could run that circuit directly to the freezer/refrigerator and get the benefit automatically...

You could make it automatic simply by adding a DPDT relay to the outlet that upon grid failure, switches the outlet from grid power to SPS power as well as turning on the SPS.

[BrianRoss]

Something about the SMA SPS does NOT add up. They are claiming that it provides enough back-up power to run a normal sized fridge, phone, TV, etc. If their inverter has these benefits - which no other inverter on the market has - then why isn't every homeowner buying this model (SMA is currently the #5 inverter in US residential market)? Does the inverter actually provide these benefits (I thought a fridge start up power is 2.4kW, so the 1.5kW would NOT work)? Are homeowners not interested in running an extension cord to these devices? Is there an issue because the solar power is intermittent, and so people don't see this as a reliable form of back-up?