BIG battery comments

[BruceS]

To anyone that has installed a BIG battery system at/near or in their home can you now comment on your thoughts?
I know Deb's dramas but even with those initial problems, is it worth it?
The premises I'm now at has a huge install of solar & is connected to the grid but like everywhere else, the rate for selling to the grid has reduced to about 8c Kwh and then as soon as the solar stops producing the rate to buy back is ?? (38c or so?)
All advice will be taken onboard & assessed !! hehe
I guess I could buy several MG's ?? !!

[supersparky]

Bruce, we don't have a battery setup, but our inverter is set to feed the house before it feeds into the grid. Our power bill is usually around $300 - $350 / 3months. We don't have a pool or use the reverse cycle airco as a heater. We have only ever got 8c/kW feed inat best. Now we are down to 3.7c/kW. We only have a 3.3kw system on the roof.
I think a battery would need to be at least as big as your daily usage and your solar double that.
If your system is over ten year old then there are some Qld govt sponsored deals going at the moment.

[BruceS]

Thanks David. The setup here is huge. 10.79kw.
The problem is still after dark. There has never been a bill since installed & every so often the request to 'pay out' is done.
I just think now I'm here plus the rate has dropped that maybe the excess could be better utilized if 'poked' into a battery for after hours consumption.
Night time use in minimal but 3 huge tropical fish tanks with heaters does bite a bit.
Until I got here the usage was one week on & one week in dongas at the mining site.

[Newcastle George]

It would have to be a very BIG battery to store the excess that a 10.7kw solar system would produce.

George

[BruceS]

For sure George but as long as it stored enough to get thru to when the solar charger took over in the morning.
I just hate the thought of the company buying my power only to rip someone else off.
As long as the battery charging system worked when excess power is generated & then like most chargers, slowly reduced charge until battery is charged.

[supersparky]

Bruce, see if you get find a few bills from Ergon/Energex for the past year or so. Find the average daily usage on the bills. Double it , for 100% usage now instead of the 50% and the get a battery that size. I need to check what our average daily usage is before I put foot in mouth for my next step.

[T1 Terry]

Worth looking at Pickles and similar on line salvage auctions for vehicles that use LFP cells .... the MG4 51 is a good example and one I can speak of with confidence.

There is a direct DC path to charging the battery that can handle up to 85kw @ 380vdc, so any solar could be rewired to an open circuit voltage of 400vdc approx. and fed directly into the battery. This can be retrieved from the battery at a rate of 7kw max 2 220vac 50 hz.

We can power everything in the Winnie that is AC powered from that. The roof top rattler, 3 way fridge, electric element in the hot water, toaster, kettle, airfryer, coffee machine, and still not reach the 7kw limit it seems .... but I haven't actually been able to test that since I rewired the rooftop rattler, fridge and water heater out of the circuit that the 16 amp circuit breaker protects and runs through an analogue meter that goes off scale past the 15 amp measurement .... and actually measure the other load that isn't monitored ...... but with all of those things powered at the same time, the 220vac remains constant .... hopefully Super Sparkie can interpret that into something useful

Buying a salvage EV will give you the cheapest big capacity battery @ $/KWH storage capacity .... I like the LFP battery chemistry because it doesn't go up in flames if something goes off kilter, it just smokes cells The MG has built in battery cooling and charging/discharging control and will not allow the battery to discharge below 25%, no over charge by tapering the charge current as it reaches 100% SOC and then engages cell balancing ..... while monitoring the voltage of every cell, 104 of them from memory ..... all in a fire proof case
The charger/inverter uses a liquid cooled controller and ..... that's getting very close to as much as I know at the moment about the whole deal

Still don't know yet how the controller knows there is DC charging current available, I'm assuming it used the same method as the AC charging via a resistor to a trigger pin in the CCS 2 plug ..... apart from getting a CCS 2 plug that has been liberated from a fast charger, I'm yet to source a supply for such a unit .... but if it came to it, I'm guessing a 3D printer could make one soon enough .....

I know how to wire the V2L (Vehicle to load) output plug from the CCS socket and where to get that plug ..... so the 7kw AC supply side is known ..... just not the DC charging of the battery

How's that for a whole lot of info to dig through in one hit

T1 Terry

[supersparky]

Terry, I've been doing a bit of reading about some of the V2L ability of some of the ever increasing fleet of EV's available in Oz. Does the inverter in your MG4 output at 50 Hz or 60?
I read on the MG forum that most of the early ones output at 60hz.
That could explain why some of the stuff in the Winny doesn't like the MG power, but is happy with the Victron.
Sorry I've dragged your thread a bit OT Bruce.

[Peter and Sandra]

Bruce we have a 3 year old Tesla Powerwall 2 which has a capacity of 14kw with about 13.5kw usable.
Solar is a 5.4kw about eight years old now
We use the two 8kw split systems to heat and cool the house as required.
In winter especially like the last one over here in the Hunter the battery has had quite a few days where it didn't get to full but the quarterlu bill was $188 so not complaining.
During summer we can run the a/c from about 9-10 am until 10 pm from the solar and battery and still fiill the battery every day.
I've investigated doubling the solar and adding another Powerwall but it would cost nearly double the original installation costs so not viable.
A vehicle with V2L sounds like the best way to go which would work for us as it's about 120km round trip to big shops and similar for beach, visiting relo's and medical other then local GP.

[BruceS]

Thankyou for your input Peter.
After just a few searches for 'solar batteries' I'm getting flooded with a multitude of companies all wanting a piece of the pie!
Sure sounds like Tesla has & will be around for a while.
BYD are catching up fast with cars & batteries etc so savage competition might reduce some costs.
To be honest as it is sure is good but I feel I should contribute simply so I can use power as I like as I acclimitize (sp?).
We are discussing building a big shed in the rear of the property & it may just be better to leave the current install alone & install a stand alone solar, battery & inverter. Doing it that way I won't need anywhere near the regulatory requirements I think?
Thousands of second hand panels around at give away prices.
The current install on the house has a facility to plug a genny in with a changover switch. Maybe a cable from shed to house in a blackout scenario?