How to add batteries & more PV

[Oldgreybeard]

Getting a separate PV inverter to turn on and sync up isn't that easy, as many do a loop impedance check before they turn on, and the loop impedance from the battery inverter may well be too high to pass that test. There are ways to do this, ranging from using a hybrid inverter for the battery system (they should stay on and run in island mode during a power cut) to using some of the better stuff, like that from SMA and Victron that can be hooked up to do this I believe.

I know that our PV inverter (a Power One Aurora) does a series of tests, like insulation resistance of the DC side, leakage current, frequency and loop impedance tests on the AC side, before it will turn on the AC side and sync up. Whether all inverters do all these tests or not I don't know. In theory an inverter that doesn't measure the loop impedance of the supply should sync up to an islanded supply from another inverter, or a generator, OK, but it's not something I've experience of.

I have been pondering ways to do this recently, as I'd like to have the option to connect a small generator, no more than about a kW, to run the house and systems if the power goes down for a few days. About 500 to 600W would be fine to keep the house going and the batteries topped up, with the batteries providing the peak power needed for short periods (mostly pumps kicking in and out). If the PV system could work at the same time that would be a bonus, even in winter, as every watt counts.

[openspaceman]

I have been pondering ways to do this recently, as I'd like to have the option to connect a small generator, no more than about a kW, to run the house and systems if the power goes down for a few days. About 500 to 600W would be fine to keep the house going and the batteries topped up, with the batteries providing the peak power needed for short periods (mostly pumps kicking in and out). If the PV system could work at the same time that would be a bonus, even in winter, as every watt counts.

Precisely my thinking too

I am only short about 450kWh November to March so a few more panels for to provide a few more days independence from imports at either end and a small Stirling chp like the discontinued baxi ecogen (if I could afford it) would see me through the year for electricity.

[openspaceman]

Info for SMA whole house backup is here, there are diagrams, but unless you have specific hardware it wont be possible to keep your Solar inverters running.

http://www.windandsun.co.uk/media/93853 ... es-v21.pdf

Thanks I'll have a read but my comprehension may be challenged