Upgrading existing off grid installation

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Upgrading existing off grid installation

Postby TsaTsa2CV » Thu Mar 16, 2017 2:42 pm

Hi everyone,
We will be upgrading our current 5.55kW, 24V Latronic LS 4024 inverter, 2 Apollo 80HV charge controllers,1680ah Raylite batteries, off grid system over the next few months. It has all performed very well with only about 200h of small geneset help in 5 years.

The current idea is to use the existing system to power the shed/studio and pool, I.e. Filters, pumps, and heatpump, garden lights, pool cover.

We propose to install a new, primary, second system in parallel, consisting of lithium iron batteries.
The idea is to have the old system act as a backup system should anything go wrong with the primary system.
So much has changed in the meantime in the battery environment that we now try to find the best way forward. We have real estate available for another 5kW of panels, north facing @ 30o°.
I like the sound of the new Tesla powewall 2 and wonder if the DC version would be suitable for an offgrid application? Could it run successfully with a SP Pro Selectronic inverter-charger? I would like to use an SPPro as the manufacturer is close to Buxton for a quick turn around, shoul anithing go wrong.

I would appreciate any useful suggestions in regards to suitable battery choice. Our average house consumption is between 7-10 kWh/day without aircoditioning. Base load is around 215W including large 2 door refrigerator and NBN satelite internet. Would 1 Tesla powewall 2 give us sufficient capacity to see us through a cloudy stretch in winter? (My be able to switch over to old system if need be). Over the past 5 years we never went below 75% SOC and I would say over 95% of the time we reach flot, even on overcast days.

Could the house/shed and pool be wired with changeover switches so as to be able to have system 1 or system 2 operating the house or the shed or vise versa. There may be times we need more power to heat the pool via heat pump or in the house for air conditioning. I look forward to your combined expertise and wisdome.

Thank you and cheers
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Re: Upgrading existing off grid installation

Postby APR » Thu Mar 16, 2017 3:04 pm

TsaTsa2CV wrote:Would 1 Tesla powewall 2 give us sufficient capacity to see us through a cloudy stretch in winter?

A Tesla Powerwall 2 is not compatible with Selectronics. Tesla have stated they are not going to sell the DC powerwall in OZ, and even if they did, it's output voltage is around 400 volt DC, not around the 50 volt required by the SP Pro.

Tesla will be selling the AC version of the PW2 in OZ, and this version is no considered to be offgrid compatible. It requires that there be excess 240v AC generation being sent to the grid, and it will grab that energy to charge itself. It is not designed to be charged by a charger such as is in the SP Pro.
2 x Goodwe GW5048D-ES Hybrid inverters, 13kW panels, 20kWh LiFePO4
Mk2 PV Router feeding excess solar generation to a 3.6kW 250 ltr HWS
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Re: Upgrading existing off grid installation

Postby Gordon-Loomberah » Thu Mar 16, 2017 3:20 pm

As APR points out, Tesla can't help you with off-grid, so maybe look at a couple of LG RESU 48V version, or DIY with some CALB or Winston cells.
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Re: Upgrading existing off grid installation

Postby davef » Thu Mar 16, 2017 3:30 pm


For LiFePO4 ...

Possibly worth a look at the SBMS120, however it will only handle 3KW of PV. With an external shunt it can handle more current on the inverter side. Only if you are into DIY.
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Re: Upgrading existing off grid installation

Postby tom rickard » Thu Mar 16, 2017 4:38 pm

If you are after LiFePO4, either DIY cells, or look at the BYD bbox system. For LiNMC look at the LGResu, or Samsung ESS. There are others but I've not had feedback on them one way or the other. The LiNMC chemistry appears to be more susceptible to degradation at high temps.

If you are looking to set the system up yourself, I have now been involved with a few systems using the SMA inverters, and it is a very simple set-up.

If you are using an installer, it's best to let them install what they recommend. Keep in mind that not all installers will either care about what is best for you, or be on top of the latest technology that is available.

You will be able to use both your systems simultaneously, just feed them through an automatic transfer switch, program one system to switch off at a certain state of charge, then it will switch to the other one.

I am in a similar situation to you, and at the moment I'm tossing up between the BYD Bbox, and DIY LifePO4 cells. Advantage of the BBox is integrated BMS that has direct comms with the SMA. Greater supply chain meaning warranty should be more reliable, and cell delivery time is short. (Some suppliers of LiFePO4 cells order every few months, so if you need them in a hurry you might be out of luck).

If you do buy a LG / BYD, and a SunnyBoy/Sunny Island combo, all of the components in your system will be readily available, and there are thousands of such systems in use worldwide, so level of understanding and support is good. If you have a component failure, it is a very simple DIY replacement.

If you get an installer and they use a mixture of components, or any components that require programming or are not very common, you run the risk of delay in the event of failure, or simply that the installer you chose no longer works in the industry. When I got my first system 5 years ago I was speaking to 4 different installers, only 1 of them still works in the industry, and they use different componentry to what they used then, and don't carry stock of what they quoted me on....

Good luck, and keep us posted on your progress.
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Re: Upgrading existing off grid installation

Postby TsaTsa2CV » Fri Mar 24, 2017 11:48 am

Tank you everyone for your time to respond to our forthcoming upgrade/duplication.

I did drop in, without an appointment to the Energymatters new office in City road South Melbourne yesterday, to have a quick look at what they could offer us, not only in Buxton, but also in town where we are just about to start with a big rebuild of our innercity grid-conected retirement house. It will have batteries and the most energy efficient, green everything. Even tough I was in the modest display looking with interest at Endphase, Sonnenshine and Tesla batteries in full view of everyone in the office for quite some time, to my great surprise, no one took a minute to asked me if they could help or tell me I needed to make an appointment to discuss our needs. I did try to ring the National number that morning but was only greeted by a recorded message to leave my details, not a real person. I suggest you could list regional numbers that get you to where you need to talk or see someone.

Anyway, as a interested participant of this great forum, I shall try to make an appointment next time we are in town.

Thanks again for your welcome feedback and wisdom

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