Grid Solar with battery

[admin]

There has been a bit of progress lately with the ability to add batteries to grid connected systems to power you through the night. Anyone done anything like this ?

I read a while ago that a bloke connected a wrecked Toyota Prius to his....apparently the battery banks in them are great

[Tiny]

While I haven't done this as I'm on a stand alone system, I do read a lot about it in the mag I subscribe to (Renew from the Alternative Technology Association).

The technology is available to do what you ask, however with the cost of supplementing or replacing your grid connect inverter with an inverter capable of handling your incoming solar array output, charging a battery bank as well as feed in to the grid, supply 240 volt power to your house system & seamlessly switching between both systems plus the cost of a sizeable battery bank to cater for your expected power usage, while still paying the power co for access to their power when you need it, is probably not going to be worth it.

Just my opinion of course.

The systems I've read about have been designed from scratch; so only one Grid Interactive Inverter purchased that is capable of all the above, plus a small battery bank only used in case of blackouts as an uninterrupted power supply type system.

[gordon_s1942]

I have seen some ads on TV recently that have given the impression of a dual Battery/Grid connection is available but what your saying Tiny that the battery is primarily just a UPS might explain what a fellow claimed he had connected to his Solar array under the roof of the house.
I have seen the battery array mounted in the house near me that is completely 'Off Grid' and there is no way you would mount that lot in the roof space.
Do they say how long a usage you would get from the UPS in a power outage?

[Tiny]

Sorry Gordon, you've misunderstood; I don't mean a little 12AH SLA's used in UPS systems that you are thinking of.

I mean a smaller battery bank than would be necessary to run a stand alone system, that is intended to only work like a UPS system.
In other words; not to be deep cycled on a daily basis.

To deep cycle the battery bank on a daily basis you need a hefty battery capacity to get any life out of them.
Hope that clears things up.

[trash]

He means the ones I have. Which total to about 10,000Ah (I've lost count).
I just picked up some grid connect inverters from my local auction.
Ever the scrounger, I paid $10 each for them. (@2.5kW).

I'm contemplating connecting one up and running both the panels and the batteries on it. It's actually not that hard to work it out when I'm the one doing the wiring.
It just requires a little careful thought.

[Softek2]

The electronics isn't the thing to be of concern. Regulations are hell bent on preventing saving money (unless there is profit for the regulators). In my experiment so fat I have found "grid connect" inverters don't have to be connected to the grid & batteries or storage is the $ per watt problem. new lithium technology is out there but expensive (& complex) right now. It is my belief that battery technology is being steered until the powers that be can find a way to profit be their existence.

[th37sk]

There has been a bit of progress lately with the ability to add batteries to grid connected systems to power you through the night. Anyone done anything like this ?

I read a while ago that a bloke connected a wrecked Toyota Prius to his....apparently the battery banks in them are great

I enquired to this when discussing options for my recent solar install (with Solar SunWerx) and the simple answer was, "Yes. We can do this for you at an additional 10K cost" (on top of $6K micro-inverted solution).
The batteries were described as large, square, flat banks and can be fitted into garage roof top space, or the like. I think the general recommendation (for my system) was about 8 batteries and they do work as you describe Admin, providing power through the night. Daniel described the functionality as charging to a specified target eg 60% capacity, then at 60% utilising what is being generated by solar, when solar is unavailable it dips into the battery bank to a specified low target (10%) before triggering power from grid/supplier. I think the general thought was not to run them bone dry for longevity. I could be off on those co$t figures. I sort of zoned out on the option once I heard, "another 10K" might have been even more.

At any rate, was advised to just go solar for now, and when banks come into their own (in the next 5-10 years) to hop on them then (as cost will be better attractive).

[admin]

Its probably about right, everything I have seen is very very pricey. But yeah, give it a few years and it should be more affordable. Thanks for the info.

[gordon_s1942]

I am sorry if my use of the word 'UPS' was incorrect, what I meant was this system would allow you to have power if the Grid dropped out but not work as a Non Grid connected system would using deep cycle battery's etc.
The lack of power during a Grid dropout (during daylight) has always been a bit of an annoyance that there you are with no power and the panels are still collecting energy from the Sun that you cant access.

I havent read up on or seen other than the TV advert I mentioned earlier so I am totally unaware of exactly what is out there in the market place.

[shred]

I have found "grid connect" inverters don't have to be connected to the grid

How did you overcome the "anti-islanding" safety feature that commercial grid-connect inverters are required to have in Australia? Some of these are quite sophisticated and in addition to checking for 230v AC being present, will periodically try to sway the frequency of the "grid" slightly. Obviously, a little inverter cannot possibly make every generator on the grid speed up or slow down, so if the inverter discovers that it can swing the frequency slightly, it will decide that it's not connected to the grid, but a little generator - and will power down.

[trash]

That was my first concern was to be careful of anything activating when it shouldn't.
I've got some normal inverters running parts of the house of the batteries, but a SPST breaker keeps them isolated.
The thought was I could just isolate rotate the contacts on the breaker and choose to have the GC-inverter on or off grid rather than choosing if the load is on/off grid.
The thought had occurred to me, would a Grid connect inverter and ordinary inverter work together in tandem.
I haven't been brave enough to even entertain the thought of testing the idea.

[Softek2]

I was also informed "it won't work" but with a little courage I started by connecting the "off grid" inverter to the system then using only one array on the grid tie i switched them together. Presto 220V @ 50.0 Hz (a preset on the off grid system). the array on the on grid inverter was 500w to start with then gradually connecting to 3Kw. So far no overheating or over voltage warnings or anything else for that matter. FWIW the off grid system is 8Kw and the house minimum draw is always >2.1Kw. To disconnect complete from the grid I had a DPDT 100amp bypass fitted (back in 1988 when mains was totally unreliable for this part of the country). I would not call it a "set & forget" system but alright for the experiment. Also the grid nowadays is reliable & consistent.

[fred121]

Gone a similar way to Softek2. Have a 4 kW grid feed system and a 4 kW battery system. Run from the grid feed during daylight hours while the battery bank (48v sun tech 1400 ah) is being charged and switch over to the battery supply during the night. Currently running credit with the electricity supplier( Aurora Tas). This setup also ensures power available when nature has a play with the trees over the lines - most recent blow took power out for 6 days but all good on the battery supply.

[Tiny]

Gone a similar way to Softek2. Have a 4 kW grid feed system and a 4 kW battery system. Run from the grid feed during daylight hours while the battery bank (48v sun tech 1400 ah) is being charged and switch over to the battery supply during the night. Currently running credit with the electricity supplier( Aurora Tas). This setup also ensures power available when nature has a play with the trees over the lines - most recent blow took power out for 6 days but all good on the battery supply.

How much does that system owe you?

What's your estimated years to recover funds spent by power saving?

Does the credit with the power co cover your network access fees or only power used?

[fred121]

Hey Tiny spent around $22k all up including solar tube hot water system. Got rebates on hot water and grid connect from govt. the batteries, actually sonnenshein, German exide, not sun tech, were secondhand about 6 years old so still some life in them, picked up an inverter and a couple of wind turbines of gumtree for next to nothing also some panels and cable (from upgraded grid feed system). Did most of install myself except for grid connect. Cost recovery around 8 years and power credit does cover costs ie no bills. Hey are you at Jackys Marsh?

[Tiny]

Hey Tiny spent around $22k all up including solar tube hot water system. Got rebates on hot water and grid connect from govt. the batteries, actually sonnenshein, German exide, not sun tech, were secondhand about 6 years old so still some life in them, picked up an inverter and a couple of wind turbines of gumtree for next to nothing also some panels and cable (from upgraded grid feed system). Did most of install myself except for grid connect. Cost recovery around 8 years and power credit does cover costs ie no bills. Hey are you at Jackys Marsh?

22k you did well for all of that; cool, Sonnenshein are great, BAE are my favourites (that's what I just bought) both are the best batteries for longevity.
6 years they were just run in.

Sounds like great set-up you have, good on you.