Inverter

An Inverter is required when you run AC equipment from a solar or battery system. It converts the DC power to AC that can be used by normal mains-connected appliances.

In some cases this can include the provision of standard GPOs in an otherwise all-DC site, for use by technicians when they visit a site for inspection or maintenance.

1) How to size a battery inverter?

The main factor in sizing the battery inverter is how much AC 'peak demand' you need to allow for.

Essentially, if the electrician gives you a "16A circuit" to provide for, you need an inverter that can deliver >16A (or for a 230V supply with 0.9 power factor that's >4.1kVA).

Where this get's complicated is because battery inverters usually have THREE output power ratings.

• A 24/7 continuous operating level.
• A 'peak demand' 30minute overload level (usually 10-30% higher than the continuous level). USE THIS ONE when matching to a 'peak demand' value provided by an electrician.
• A 'surge demand' 3-5seconds overload level (usually about twice the continuous level).

It can then be further complicated by temperature!

Most inverters will operarte at full capacity up to ~40*C (Pascal, can you swap the * for the proper 'degrees' symbol). But if the machine temperature rises above the manufacturer's nomindated level it will de-rate it's output to prevent damage to it's components.

If you expect the inverter to exceed 40*C, ensure that the de-rating is factored into your sizing calcs, or consider installing forced ventillation or even air-conditioning (since none of the other hardware is particularly fond of high temperatures either!).

Other sizing things to consider would be to obviously match the inverter to your battery voltage and to pay attention to your DC wiring and fusing (you may need to allow for some fairly high currents so always watch your cable ratings and voltage drop calculations).

2) Does the battery inverter include LVD?

Mostly, yes, but check the individual manufacturer/model info to be sure.

Some models may give you the option to program the voltage level at which the LVD kicks in. Some may even allow you to disable it altogether. But it is a standard feature on pretty much all battery inverters.

3) What types of 'user interfaces' do battery inverters offer?

This varies enormously by manufacturer and by model.

For some it's as simple as a handful of LEDs to indicate various status modes.

Others may have a built-in or peripheral digital display screen.

Still others may offer Bluetooth or WiFi interfaces to a manufacturer's App.

And then other models allow coms integration to other devices and ultimately the web for remote online monitoring, reporting & even updating.

Pick whatever options suit your needs!

4) Delivering 1ph vs 3ph with battery inverters?

Almost all battery inverters provide only 1ph AC outlet.

To provide 3ph you will need 3 separate 1ph inverters. In order for them to operate properly as a '3ph supply' (i.e. correct phase angle etc) you will need to use models that have a coms inter-connectivity function so they can be configured as Master-Slave units to provide the correct 3ph waveform.