Choosing a Battery-Based Inverter: Page 3 of 3

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Magnum Energy’s off-grid inverter
Magnum Energy’s off-grid inverters have optional remote metering and now carry a standard three-year warranty. A standard five-year warranty is offered, but only if the inverter is wired and mounted on Magnum BOS systems.
The inverter is wired and mounted on Magnum BOS systems.
Magnum Energy’s off-grid inverters have optional remote metering and now carry a standard three-year warranty. A standard five-year warranty is offered, but only if the inverter is wired and mounted on Magnum BOS systems.
The OutBack Power off-grid FX series inverter
The OutBack Power off-grid FX series inverters come in vented (shown) and sealed models. The sealed model is recommended for harsh environmental conditions (high humidity and corrosive salt air). The vented model supports high AC output power in hot environments.
OutBack Power’s new Radian series inverter
OutBack Power’s new Radian series inverter can be installed in off-grid or grid-tied systems. It has an 8,000-watt output rating, and offers split-phase 120/240 VAC output and dual AC inputs.
OutBack Power’s line of GT inverters
OutBack Power’s line of GT inverters are built strictly for grid-interactive usage and are not designed to be used with a generator. Like the off-grid series, the GT models are offered in sealed and vented models.
The OutBack Flexware 1000 system integration hardware supports up to four inverters and accommodates the charge controllers.
Inverters can be stacked for higher voltage, more current, or for multiple phases. This OutBack Flexware 1000 system integration hardware supports up to four inverters and accommodates the charge controllers and all required AC and DC balance-of-system components.
SMA America’s Sunny Island inverter
SMA America’s Sunny Island inverters can be used in both offgrid and on-grid systems, and support AC coupling to Sunny Boy batteryless grid-tied inverters. (Note: Two Sunny Island inverters are required for 240 VAC output to AC-couple to Sunny Boy inverters with 240 VAC output.)
The Schneider Electric XW series inverter
The Schneider Electric XW series inverter also can be used in either off-grid or grid-tied systems. It has 120/240 VAC split-phase output and dual AC inputs. The complete XW system shown here includes AC and DC balance-of-system equipment on the power distribution panel.
Exeltech MX inverter
Exeltech MX inverters can be configured in 1 kW increments up to 20 kW at 120V; in 2 kW to 40 kW at 240 V; and in 3 kW to 60 kW at 208 V three-phase. Up to 5 kW will fit into a “cage” at 120 V. Two cages are required for 240 V (one cage for each phase), which are bolted together as a single unit. Three cages are used for 208 V three-phase.
The Apollo TSW inverter
The Apollo TSW inverters offer 120/240 VAC split-phase output/input.
Magnum Energy’s off-grid inverter
The inverter is wired and mounted on Magnum BOS systems.
The OutBack Power off-grid FX series inverter
OutBack Power’s new Radian series inverter
OutBack Power’s line of GT inverters
The OutBack Flexware 1000 system integration hardware supports up to four inverters and accommodates the charge controllers.
SMA America’s Sunny Island inverter
The Schneider Electric XW series inverter
Exeltech MX inverter
The Apollo TSW inverter

Search Power ratings reflect the energy-saving “search” or “sleep” mode available in most off-grid inverters. This mode allows the inverter to nearly shut off during times of no-load draw. While the inverter still consumes some power to monitor household loads, the search power consumption is commonly about 75% less than the no-load consumption. Depending on the inverter “wake-up” wattage threshold, there may be some small AC loads that will no longer work if nothing else is turned on. Small, always-on AC loads (security systems, clocks, answering machines, etc.) can keep the inverter awake, consuming energy all of the time. For small loads, one tactic that can work is to shift to a consumer battery (like AA rechargeable) counterpart. Another tactic is to include a small, always-on inverter that is dedicated to those household appliances.

Integrated Battery Charger/Maximum DC Amps—Most of the inverters in the table include battery chargers that work on an AC power source (see the “Integrated Battery Charger” sidebar). The battery charger has a maximum DC current rating that will limit how much from the available charging source can be used. While the generator may be adequately sized, a lower battery charger limit can increase generator run time. One strategy is to install multiple inverters/chargers, which increases battery charger capacity. Ideally, the generator will be sized according to charger capability (see “Engine Generator Basics” in HP131).

Generator Start enables inverters to remotely start and stop a generator. Users can select a low battery voltage value that triggers the inverter to initiate a generator start and run sequence to charge the batteries. Other parameters can also be set to run the generator during times of high power consumption and/or during specific times of the day. While this feature can be handy, there are drawbacks (see “Automatic Generator Start” sidebar).

Dual AC Inputs allow users to use more than one AC power source, such as the grid and a generator, for battery charging. This is useful in grid-tied systems with battery backup, since it allows charging batteries from the grid when it is available and from an engine generator during times of utility outages (and low RE-system output), offering another source of backup power.

Remote Display is useful for keeping tabs on the system from a convenient location (such as the kitchen). These displays usually include user buttons to turn the inverter on and off, and to adjust programmed settings.

Prepackaged with Balance of System Equipment can be a time-saver when it comes to installing a battery-based inverter, since these systems have many components that need to be wired and located in the vicinity of the inverter and battery bank. These additional components are required in battery-based systems because there are multiple power sources (such as a PV array, batteries, generator, and the utility grid), and it is required to have disconnects and overcurrent protection between each system component and each power source. Other components can include charge controllers, meters (and shunts), ground-fault protection devices, inverter bypass assemblies, and communications hubs. Additionally, all of these components need a backplate to be mounted on and neatly fitted and wired together, further increasing the time and hassle savings offered by optional prepackaged power-panel assemblies.

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Justine Sanchez is a Home Power technical editor and an instructor for Solar Energy International. She is certified by ISPQ as a PV Affiliated Master Trainer.

Comments (4)

martin sattler_2's picture

Is this article from a HOME POWER print Issue? The date or Issue Number is not given. I have all back issues and would like a cross reference. Thanks, Martin

Scott Russell's picture

Looks like June/July 2012, Martin. Issue #149.

Justine Sanchez's picture

Hi George, yes they will need to invest in a battery-based inverter, and will need to separate out the loads they want to be backed up into a critical load sub panel, that will be powered from the battery-based inverter (that also has the ability to pull from the utility when present). I encourage you to check out some of our previous articles on GT systems with battery backup, such as this one from Flint Richter:
http://www.homepower.com/articles/g...
Cheers,
Justine
Home Power Magazine

George Wear's picture

Hi Justine, I have a grid-tied client in Hondurus where outages are common and power is expensive, but the grid will not accept any excess power generated. They want to start small with a backup system to power a critical load panel. Will they need a special inverter or special wiring in order for this?
thanks, George

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