Model S backup to grid and powerwalls

[smuseby]

This month, we lost PG&E power for 2 days, my two powerwalls worked for about 10 hours, and there was no sun to recharge the powerwalls. The last resort is the 100 kwHr battery in the garage.

I connected a 1kw inverter to the 12v battery with 2 gauge cables and Anderson connectors, and 12' of 14 gauge extension cord to my refrigerator. and longer extension cords to my modem, router and computer. The electronics worked nicely, but the inverter was not able to deal with the start-up current required by the refrigerator compressor.

I'd like to buy a bigger inverter, but since I have bypassed the car's fuses, I want to be careful and not exceed the capability of the DC-DC charger in the car.

How much power can the Tesla safely deliver? i.e., how big an inverter can I buy for this Tesla hack?

 

[jjrandorin]

I dont know about model S, but we have a thread in the model 3 subforum on this topic. Its not one that interests me but perhaps you can get some ideas from that thread? I realize its model 3 vs S but some of the information may help you, perhaps.

MASTER THREAD: Powering house or other things with Model 3

So I came home to a power outage last night, ah mountain living. As I am burning the lamp oil for light, and hating the fumes I start to wonder why I'm sitting in the dark with 40 kWh in the battery sitting in my driveway. I decided to plug a small inverter into my cigarette lighter in my...

teslamotorsclub.com

 

[Watts_Up]

This month, we lost PG&E power for 2 days, my two powerwalls worked for about 10 hours, and there was no sun to recharge the powerwalls. The last resort is the 100 kwHr battery in the garage.

I connected a 1kw inverter to the 12v battery with 2 gauge cables and Anderson connectors, and 12' of 14 gauge extension cord to my refrigerator. and longer extension cords to my modem, router and computer. The electronics worked nicely, but the inverter was not able to deal with the start-up current required by the refrigerator compressor.

I'd like to buy a bigger inverter, but since I have bypassed the car's fuses, I want to be careful and not exceed the capability of the DC-DC charger in the car.

How much power can the Tesla safely deliver? i.e., how big an inverter can I buy for this Tesla hack?

- You should measure the in-rush current for your refrigerator.

Typically the in-rush current would be about 5 time the nominal compressor steady state.​

This will help you determining the size of your inverter.​

Adding some capacitors could help reducing the sudden inverter load.​

- The Tesla battery is very small, I would recommend adding an external larger battery.

You should connect your inverter directly to the external battery.​

And add a fuse between the negative inverter connection and the negative external battery.​

​

I would not connect the inverter directly to the Tesla battery​

but use the 12V auxiliary plug to connect the two batteries.​

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This would protect the Tesla 12V battery and will allow you to get an extra boost when the refrigerator starts.​

The Tesla battery and the external battery then could be charged by the Tesla DC/DC inverter charger.​

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