{"id":99,"date":"2020-06-08T15:15:00","date_gmt":"2020-06-08T22:15:00","guid":{"rendered":"http:\/\/www.cafeelectric.com\/blog\/?p=99"},"modified":"2023-12-20T10:06:32","modified_gmt":"2023-12-20T18:06:32","slug":"inverter-power-connection-1","status":"publish","type":"post","link":"https:\/\/www.cafeelectric.com\/blog\/2020\/06\/08\/inverter-power-connection-1\/","title":{"rendered":"Model 3 Inverter Power Connection"},"content":{"rendered":"\n

Not ideal, but it works with some babysitting. <\/h4>\n\n\n\n

For more AC power than a standard 12V Power Socket inverter could provide, I tapped into the high current DC-DC output from the Tesla PCS (Power Conversion System) under the rear seat.
This is a first trial, not very refined, but functions well with manual Inverter switching assuming it is disconnected from the car during firmware updates. <\/p>\n\n\n\n

The Gritty Details<\/h3>\n\n\n\n

First of all, the only Tesla sanctioned 12V supply that I know of in the car is the 12V Power Socket. As you can see below, it is rated for 12 Amps continuous load. Although a small inverter or my refrigerator can be run from this outlet, it’s not powerful. After losses it will only supply ~110 Watts of 120V AC power. <\/p>\n\n\n

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The owners manual has this to say about the !2V Power Socket<\/strong><\/figcaption><\/figure>\n<\/div>\n\n\n

My desire was to run a juicer while camping using a low cost inverter from Harbor Freight. The one I used is rated for 750 Watts continuous, 1500 Watts peak and has been running my juicer and rice cooker for many years on camping trips. <\/p>\n\n\n

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[EDIT, It seems to be discontinued. I have not tested another for the necessary no load when turned off yet. Comment please if you know one.]
https:\/\/www.harborfreight.com\/automotive\/automotive-accessories\/inverters\/750-watt-continuous-1500-watt-peak-power-inverter-66817.html<\/a><\/p>\n\n\n\n

Traditionally an inverter like this would be connected directly to the 12V battery on your car, on a Tesla Model 3 it’s not so simple. Due to the battery monitoring device built into the Model 3 VC Front (front vehicle controller) extra loads on the 12V battery will cause the Tesla software to register a fault of the battery. Therefore we need to find another place to tap high current 12V power that won’t upset the Tesla systems.

NOTE: If you have already tripped a persistent fault of your 12V battery that doesn’t clear when the car sleeps, it can be cleared by a full shut down of the 12V and HV batteries (penthouse low voltage connection) for 30 seconds. The sequence is a bit important so it would be advisable to consult the Tesla service manual procedure for that.<\/p>\n\n\n\n

Fortunately there is a high current 12V connection to the DC-DC converter under the rear seat. The VC Front has an e-Fuse that disconnects this terminal from the 12V battery when the car is asleep, but as long as the car is awake the connection provides high power from the high voltage traction pack through the DC-DC converter in a way that does not cause the car to flag a bad battery. This should be safe to use when the car is parked. I would not draw high current when driving since it is important to have enough excess current budget available to run the critical vehicle loads including power steering and brakes.

Pictures below show my setup with a 100 Amp fuse and #6 AWG wiring leading to an Anderson SB-50 connector https:\/\/amzn.to\/2YfpX2P<\/a>* mounted under the package shelf. Additionally there is a smaller Anderson Powerpole connector with a 15 Amp fuse for plugging in the refrigerator.<\/p>\n\n\n\n

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This is where it gets complicated.

Although the refrigerator had no trouble running when the car was awake, and worked fine, the AC inverter caused a problem. The AC inverter has relatively large DC filter capacitors connected to the DC input terminals. Rapidly filling these capacitors is what causes the familiar spark when an inverter is connected to a battery. In my experience, approximately half the time that the car woke up, the inrush surge to the inverter would trip the e-Fuse that connected the DC-DC to the vehicle systems resulting in this unwanted fault.<\/p>\n\n\n

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Fortunately, walking away from the car with Sentry, HVAC and Summon Standby Mode switched off and waiting a few minutes (or longer if the 12V battery is charging) will allow the e-Fuse to reset. As far as I can tell, the car just needs to go to sleep to reset it. <\/p>\n\n\n\n

Precharge Circuit<\/h3>\n\n\n\n

In order to avoid tripping the e-Fuse we need a way to gradually fill the capacitors in the inverter and then activate a relay connecting the inverter insuring low inrush current. This is commonly known as a precharge circuit.

I wanted to keep things relatively simple so some compromises were made: <\/p>\n\n\n\n