Incorporating an off-grid battery and inverter camping system into home?

[Dawie]

Hi Everyone,

I'm a complete novice in this area and new to this forum, which I came across when searching for some info on-line.

In short, our home has a grid connected 10.73 KW solar system with Fronius Primo 8.2-1 Inverter and Fronius Smart meter. My understanding is that this is a “battery ready” system however we have not yet added a battery. I'll try and add a pic of the web interface for our system, which indicates it does cater for a battery?



At this stage surplus energy is fed back into the grid however the Feed In tariff is very low and, as I do have a camping set-up configured for induction cooking, I was wondering whether this could somehow be incorporated to utilize the batteries? It basically consists of 2 x 200Ah LifePo4 batteries in parallel with own internal BMS and a 3000W Pure Sine Wave Inverter. I was therefore wondering whether these batteries can be connected to the current Fronius Primo 8.2-1 inverter to power certain circuits in the home when there’s no solar power (e.g. at night) and, if not, whether the 3000W inverter can somehow be used for this?

If indeed possible, could one then just add additional batteries (of same spec) to increase capacity as required?

Would appreciate input and thoughts from those in the know...

Battery Spes:
Chemistry: LiFePO4 (Lithium Iron Phosphate)
Watt hours: 2560WH
Voltage: 12.8V
Charge voltage: 14.6V
Discharge cut-off voltage: 10V
Max recharge current: 150A
Max continuous discharge: 150A
Max pulse discharge (10 seconds): 300A
Operating temperature charging: 0°C TO +60°C
Operating temperature discharging :-20°C TO +60°C

Inverter specs are:
Wattage: 3000W
Output Waveform: Pure Sine Wave
Input Voltage: 12VDC
Input Current: 284A
Output Voltage: 240VAC
AC Frequency: 50/60HZ
Efficiency: >85%
Power Usage On Standby Mode: <2A
High Voltage Shutdown: If the 12V DC battery reaches 15V (±0.5V) the inverter will automatically turn off.
Low Voltage Shutdown: If the 12V DC battery reaches 10V (±0.5V) the inverter will automatically turn off.
Thermal Protection: If the temperature rises to above that for the inverter to operate safely, the inverter will turn off. When the temperature reaches a safe level, the inverter will turn back on.
Overload Protection: If the inverter detects a load power that exceeds 3000W the device will automatically turn off.
Short-Circuit Protection: If the inverter short-circuits, the fuse will disconnect, protecting the unit.

Cheers
Dawie

 

[sunshine_eggo]

Many are told that their grid tie inverters are "battery ready," but many are lied to.

Do you have any objective evidence that your inverter is actually "battery ready?"

If this is your unit:

https://www.fronius.com/~/downloads/Solar%20Energy/Datasheets/SE_DS_Fronius_Primo_EN.pdf

I don't see any mention of "battery ready" or other hint that one simply needs to add batteries.

However, your idea of a separate inverter with battery is mostly valid; however, the unit you have specified will almost certainly be destroyed if coupled with the Fronius.

Your system can likely be "AC Coupled" to an off-grid inverter capable of AC Coupling and "frequency shifting." That inverter will need to be at least as powerful as the lesser of your inverter's rated output power, or your installed solar.

 

[Dawie]

Thanks for that mate...

I posted a link to the inverter I have in my original post and yes, it's one of the units listed on the datasheet you posted. My understanding is that the unit is ready to take an AC coupled battery so yes, won't work with my current batteries without spening $$ on additional hardware.

As my current avg net monthly bill after credits for selling back to the grid is around $40 pm and, based on quotes I got, investing in something like a Tesla Powerwall will equate to a 30+ year payback whilst it has a 10-year guarantee and, depending on usage, a life-expectancy of 20 years. So, at least in my scenario, not worth it at this stage. Was just hoping I could off-set some of my peak-hour consumption in mornings and evenings when there's no sun, by utilizing the camping setup sitting around doing nothing, but that kite's not gonna fly without spending more $$.