Can You Charge A Tesla Model 3 With A Petrol Generator?

May 28, 2023

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I have just spent the morning with the technical staff at Glenco Air & Power, experimenting with their Westinghouse portable generators and my Tesla Model 3. No one got hurt. The car didn't blow up. Curiosity was satisfied. We now know why my Tesla Model 3 would not accept an emergency top-up charge from a petrol generator.

This particular science experiment grew out of a shared experience at the Goomeri Off Grid Lifestyle Expo, where I was suffering from range anxiety 3 months prior. In need of a top-up charge, I first tried my friend's BYD T3 van, but it could not export enough power. Then the helpful staff at the Westinghouse Outdoor Power Equipment stand offered to try. The chosen generator and the car would not cooperate on that day, and we were left with a puzzle. Why couldn't we charge the Tesla with a petrol generator? The short answer as we discovered today is that the car was searching for a "multiple earthed neutral" (MEN) system of earthing on the external electricity supply. Not all electric vehicles have this safety feature, it seems, but Tesla does. Note that in Australia it is mandatory for electrical installations in buildings to have this feature, so Teslas can be charged at home easily.

The engineers at Glenco are intelligent, curious, and tenacious. Over the past 3 months, they did research, even read the Tesla manual, visited the local Tesla showroom, and today tested the theory at their workshop. We hooked Tess (my Tesla Model 3) up to their mains power supply and checked the baseline condition using both the 10 amp and 15 amp Tesla charging cables and taking measurements with a Fluke 435 Power Quality and Energy Analyzer.

Engineers and technicians checking out Tess. Photo courtesy Majella Waterworth.

Incidentally, there is no guidance in the Tesla instruction manual about charging using a generator.

Setting the baseline with the Fluke. Photo courtesy Majella Waterworth.

This was the comment from Tesla technical support when we tried the experiment with an IGEN4500s as the Tesla searched for a suitable MEN system: "We reviewed and found high ground impedance detected by the UMC. The UMC will not allow charging until the protective earth connection is corrected at the generator."

We then double checked the charging capabilities of the generator we used at Goomeri, which does not have a MEN system of earthing. Once again, it could not charge the car. Then, the Glenco technicians switched to using a Westinghouse 3750-PRO portable generator with a built-in residual current device (RCD, also known as a "safety switch"). The RCD mimics the MEN configuration and the car responded by accepting the electrical charge from the generator.

Not all EVs are the same, and owners will need to check out the charging needs of their individual cars. Paul Korganow, the owner of Glenco and an engineer by profession, urged caution when buying a plug-in "caravan power adaptor with built-in RCD" for use with a conventional generator that doesn't have its own built-in RCD. This combination does not provide a MEN earthing system. We tried this setup on Tess and sure enough it wouldn't charge.

For more information about the range of Westinghouse PRO-Series generators with built-in RCDs, you can click here.

I learned a lot this morning, old knowledge that is not quite common in society. Now, if I could just get that electrical information to replace the mechanical information in my head.

It is testimony to the staff at Glenco that they followed this issue through to the solution. Like Paul said, "We take customer concerns seriously." They certainly do.

David Waterworth is a retired teacher who divides his time between looking after his grandchildren and trying to make sure they have a planet to live on. He is long on Tesla [NASDAQ:TSLA].

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