Hi all. I’m a complete noobie, so apologies in advance. I’m a first time EV owner (Audi e-tron), with solar panels and a Powerwall 3 at home. Can anyone here advise me if it is possible to charge my Audi in the evening (no solar) and use the Powerwall to supply rather than the grid? Or is it simply not possible to use the Powerwall supply for charging the car? Thanks all.
Hi, The problem will be that the Audi has a battery capacity of around 95 kWh which is over 7 times that of a Powerwall so charging from the Powerwall will not be possible for more than a small top-up. Generally it’s not recommended to use a home battery to charge an EV due to the capacity difference and as you will both flatten the Powerwall for home use and reduce its lifetime in terms of battery use cycles for no real benefit.
Hopefully V2H/V2G moves ahead and EVs such as yours can start serving double duty as home storage in their own right.
Many thanks for that - what you say makes a lot of sense. Looks like I should move from a solar energy plan to an EV charging plan with cheaper night rates. Thanks again!
The best ROI for solar is by consuming it yourself as it is generated as this offsets imports so has that value per kWh to you which will always be higher than export rates. Using an EVSE (‘charger’) that has solar diversion is a great way to maximise your self consumption if you are able to charge during the day.
Also so far as supply/FITs (Feed In Tariffs) are concerned Octopus are a good option as they have decent export rates and a low night rate. The only caution is if your solar has more than 10 kW of capacity as Octopus force you into their Peaker plan then which has much less attractive FITs as suited to those with batteries so a bit more work involved in scheduling your export ex-battery.
We have 13.2 kW of inverters over two phases with no batteries so changed to Ecotricity when our latest upgrade put us over 10 kW. Ecotricity also add GST to your export due to the way their invoices are set out, whereas Octopus don’t.
I will charge the Audi during the day and it’ll be my partner’s Fiat 500e that will be getting charged in the evening - hence my question about the battery. Sounds like we should stick to grid charging for her evening charge and solar diversion for me during the day (we have a 8.3kW solar setup). I have a great export rate deal with Meridian with a very low daily charge. Thanks for the Octopus info. Looking forward to getting the Evnex installed so I can start properly using the solar!
Be careful with solar diversion. I have a Sungrow inverter and battery system and once my charger started charging in solar diversion mode, it couldn’t recognise how much excess solar was being generated and started being fed from the battery when excess solar fell below the charging rate. My charger is part of the protected house load from the inverter’s perspective.
Thanks Stephen - certainly something worth looking out for when my system is up and running!