question

dochero avatar image
dochero asked

Building a system: inverter advice for 60kwh battery

We use a lot of electricity (no gas, so heating and cooking are all electric; ASHP and induction hob). We're using about 40-50kWh/day averaged over the year. Hence, I'd love to be able to store 50+kWh off-peak. We also have a 4kWp solar system with a Sunny Boy inverter.


If I buy a used EV battery, e.g. from an MG ZS or MG 5 or Nissan Leaf, what's the best way of wiring up and which inverter would be best? My current thoughts are to remove the modules from the EV battery (~18 modules) and have them in the house. Are there any dangers there? Otherwise, I can build a small shed for the entire EV pack and wire that in - but I can only find very DIY approaches there e.g. Dala.

As far as the system goes, I could either replace the Sunny Boy inverter with a Quattro (e.g. 48/8000) or add the quattro and some more solar panels (another few kWp).

We do also have a Nissan Leaf and have been planning to upgrade the battery, but I think the capacity here is only 20kWh. If this is much easier to set up it'll be considered. I haven't found any ways of bi-directional charging at reasonable cost (V2G/V2H), which would have been my preferred method.

Any input welcomed!

MultiPlus Quattro Inverter Chargerstorageev and storage
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1 Answer
Jason - UK avatar image
Jason - UK answered ·

@dochero You have a similar consumption as I do. Im currently using 4no Tesla Model S modules connected to my Multiplus II GX 5kva unit. My current energy tariff is the Octopus Go so I do as much during that 4 hour window, bring my peak time consumption down to about 20-30kWh. My battery storage is only 21kWh so for the 1% of the year I run of of battery power, I pull from the gird but the capital cost for that extra 10kWh is not worth it within my ROI / calculations.

I would keep your PV system as it is and have is on the AC-out1 side of a Multiplus II. Not the most efficent as you have your PV invert losses of say 10% converting from 400v DC to 230v AC, then the Multiplus converting it from 230v AC to 48v DC, to then convert it back later when you want to energy, 48v DC back to 230v AC, giving to a 30% loss as a rule of thumb. PV direct into the battery is more efficent but then you dont have the option to 'generate' a large kVa. With my system having the 5kVa Multiplus and a 5.7kVa solar inverter, I have to total generation capacity of 10.7kVa. If that solar energy went direct to the battery, I would be only able to generate 5kva with only 1 5kVa Multiplus.

The best of both worlds is to have both a AC PV system on the AC out, and another PV system, DC direct into the battery.

https://vrm.victronenergy.com/installation/171934/share/db6807bb

My schematic is on the above link in the photos section.

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