Off-Grid Inverter Question

[Murby]

Does anyone make an inverter that can send power directly from the panels to a 240 volt system if a battery bank is depleted?

[jflorey2]

Does anyone make an inverter that can send power directly from the panels to a 240 volt system if a battery bank is depleted?

Sure, every string inverter out there will do that; they backfeed 240V to the grid.

If you want to do that without a grid (or batteries) present right now your only option is the SMA Secure Power option. It's 120V but you can use a transformer to get to 240V.

However, your question doesn't make a lot of sense. If you have no power from the solar arrays, and no energy in the battery, you can't do anything at all. If you have power from the arrays and no energy in the battery, you can charge the batteries and run a conventional inverter with the power. You don't even need to be charging the batteries. As long as your outputs match your inputs the voltage will remain fairly constant and the inverter will work.

[SunEagle]

The question is kind of suspicious.

Do you want a legal hybrid grid tie system or are you looking to somehow send power to the grid illegally from an off grid solar/battery system?

[inetdog]

If the battery bank is depleted (low enough SOC that you do not want to draw it down any further) the inverter (off-grid or hybrid) will continue to work just fine as long as the panel power is enough to meet your loads.
If the battery bank is damaged (cannot safely deliver or accept current at its nominal voltage) then no inverter will continue to work except a pure grid tie inverter.

[Murby]

Perhaps I should have been more clear.
In an off-grid situation, is there an inverter out there that can utilize the full power of the solar panels and output 240 volts?

For instance, lets assume the battery bank is fully charged and I want to run a 240 volt load but I don't want to drag down my batteries.. The sun is shining and I want to use the excess power directly from the panels instead of putting the drain on the batteries which I might want to save for later.

Are there any inverters out there capable of doing this? Or is the only option a battery powered inverter?

I have an SMA grid tied system with a 2000 watt secure power supply.. I'd like to purchase an inverter that can do the same thing only with much larger capacity. I know there are no grid tied systems so I'm wondering about off grid systems.

[ButchDeal]

Perhaps I should have been more clear.
In an off-grid situation, is there an inverter out there that can utilize the full power of the solar panels and output 240 volts?

For instance, lets assume the battery bank is fully charged and I want to run a 240 volt load but I don't want to drag down my batteries.. The sun is shining and I want to use the excess power directly from the panels instead of putting the drain on the batteries which I might want to save for later.

Are there any inverters out there capable of doing this? Or is the only option a battery powered inverter?

There are two kinds of systems with batteries. DC coupled and AC coupled. The majority of the bimodal systems are DC coupled.
There is no magical switching of the current from battery to inverter though.

The charge controller puts power on the DC bus. Both the inverter and the batteries are on the bus. IF the inverter pulls power at a rate less than the charge controller is putting out then the inverter is not pulling from the batteries (in fact the batteries are being charged).
If the inverter pulls at a rate higher than the charge controller is putting out then it will pull from the batteries AND the charge controller (discharging the batteries).

There are bimodal inverters that are 240V and there are ones that are 120V that can stack to make 240V.

I have an SMA grid tied system with a 2000 watt secure power supply.. I'd like to purchase an inverter that can do the same thing only with much larger capacity. I know there are no grid tied systems so I'm wondering about off grid systems.

there are no inverters that can provide insecure power like the SMA at 240V, or that can be wired in to your service panel that do NOT have batteries.
There are many that can do this and much more securely, can be wired in, and have batteries.
Outback makes quite a few and they are grid tied as well.

[SunEagle]

Perhaps I should have been more clear.
In an off-grid situation, is there an inverter out there that can utilize the full power of the solar panels and output 240 volts?

For instance, lets assume the battery bank is fully charged and I want to run a 240 volt load but I don't want to drag down my batteries.. The sun is shining and I want to use the excess power directly from the panels instead of putting the drain on the batteries which I might want to save for later.

Are there any inverters out there capable of doing this? Or is the only option a battery powered inverter?

I have an SMA grid tied system with a 2000 watt secure power supply.. I'd like to purchase an inverter that can do the same thing only with much larger capacity. I know there are no grid tied systems so I'm wondering about off grid systems.

Ok. So you are looking for a device that converts the DC from the entire solar pv system to AC 240V and not be connected to the grid.

I am not aware of any device that can convert the DC to AC without having a battery source in between except for a grid tie inverter. Although that does not mean someone doesn't make that type of unit.

[jflorey2]

In an off-grid situation, is there an inverter out there that can utilize the full power of the solar panels and output 240 volts?

Nothing "native." As I mentioned, you can get up to 2000 watts at 120 volts from an SMA inverter without batteries, then use a transformer to boost it to 240V. There are no grid tie (i.e. batteryless) inverters out there that will do this without the transformer.

For instance, lets assume the battery bank is fully charged and I want to run a 240 volt load but I don't want to drag down my batteries.. The sun is shining and I want to use the excess power directly from the panels instead of putting the drain on the batteries which I might want to save for later.

Then just do it. Your batteries will not be drawn down as long as the available power from the panels exceeds your 240 volt load.

I have an SMA grid tied system with a 2000 watt secure power supply.. I'd like to purchase an inverter that can do the same thing only with much larger capacity. I know there are no grid tied systems so I'm wondering about off grid systems.

Any off grid inverter will need SOME storage. It could be a battery bank or an ultracapacitor bank but you will need something, for two reasons:
1) Inverters are designed to work with low impedance inputs, not the higher impedance input of a solar array (or the output of an MPPT.)
2) Most AC loads have some surge associated with them. You need some storage to provide power during that surge. The alternative would be to put in a 20kw array to handle a few kw of load, which isn't economical.

[Murby]

Thanks for the replies everyone!

[Mike90250]

I'm off grid, and when batteries are full, I can add 240V loads till I match the output of the solar array. Manually. Don't know of any way to do it automatically.

[Murby]

I'm off grid, and when batteries are full, I can add 240V loads till I match the output of the solar array. Manually. Don't know of any way to do it automatically.

You're off grid so you have a 240 volt split phase inverter/charger hooked to a battery bank yes? Does the power go directly from the panels to your load or does it have to go through the battery bank first?

[ButchDeal]

Does the power go directly from the panels to your load or does it have to go through the battery bank first?

The power does not go "through " the batteries on a DC coupled system. It goes BY the batteries.
The Charge controller, Inverter, and batteries are all on the same bus.
The power does not instantly charge and discharge from the batteries. At any instant you are either charging or discharging the batteries or neither but not both.

[Mike90250]

You're off grid so you have a 240 volt split phase inverter/charger hooked to a battery bank yes? Does the power go directly from the panels to your load or does it have to go through the battery bank first?

Yes, I'm off grid. split phase 240V inverter. [ XW-6048 Xantrex / Schneider] Everything hooks to the batteries, Solar Charge Controllers, backup AC charger, XW-6048 inverter/charger. I manually monitor and have designed to prevent excessive battery depletion,

[NEOH]

With a Sunny Boy + Sunny Island setup, the Sunny Boy(s) will generate the 120 VAC directly to the in-home micro-grid & power devices, then the Sunny Island would charge the battery bank.

[littleharbor]

SMA makes some quality inverters but this particular setup is quite expensive. Their Sunny Island Inverters are not for the budget minded.