Facebook Marketplace exists for two reasons: Wasting time at work and buying junk that ran when parked. You can find golf carts on there all day long that are in near-perfect condition, save for some dead batteries, and they’re usually cheap. The problem is that new batteries can cost around $1,000 to swap in, suddenly making your project a whole lot less affordable. But what if I told you there’s a cheaper way to get them back in action around the cul-de-sac, all without buying a bunch of big, heavy 12-volts?

It’s a pretty ingenious Harbor Freight solution cooked up by the guy behind the Robot Cantina channel on YouTube. Affectionately named Jimbo, he has a reputation for this type of lowkey genius DIY tomfoolery. We’ve written about his Kubota diesel-powered Honda Insight more than once, though that’s far from the only other project he has going on. He’s worth the follow, for sure.

Jimbo’s latest video shows him testing the prototype for his “petroleum battery” powertrain in an old Cushman cart. It’s still driven by an electric motor, but the juice for said motor is supplied by a 212cc Predator engine from Harbor Freight that’s hooked to a 140-amp alternator. You could presumably use almost any automotive alternator, though Jimbo says they plucked one from a Jeep Liberty because it was free.

The rest of the parts list is pretty short and simple, at least for this iteration. In addition to the Predator engine and Jeep alternator, Jimbo’s setup includes a pulse-width modulation (PWM) power supply, an emergency stop switch, an accelerator pedal he bought off Amazon (which he calls “the jungle site”), and a single 12-volt battery to provide the juice needed upon startup. Even with all this, Jimbo claims it’ll shave roughly 270 pounds compared to a normal golf cart’s series of batteries.

“The way we’re using the alternator as both a power source and a DC motor controller is unique, and it’s important to understand this is not a conventional way to use an alternator, “Jimbo says in the video. “Once you wrap your head around the fact we’re using the alternator as a DC motor controller, it becomes clear why we don’t need any extra stuff like batteries or supercapacitors in this very, very, very simple system.”

Now, there are important tidbits to consider with this setup, and your mileage may vary depending on the exact components you use. In Jimbo’s case, he had to sever the connection between a brush on the alternator and the unit’s casing in order for the PWM to work properly. This is where it helps to have some electrical know-how, and as much as I’d love to say otherwise, I’m far from an expert on that.

With the minor alternator mod complete, Jimbo’s ready to test the powertrain in the Cushman. It’s important to note that in order for all this to work, the Harbor Freight engine needs to run around 3,600 rpm. Once that’s set, the alternator can work up enough juice to power the DC motor. The PWM has a twist knob to modulate how much power flows from the alternator to the motor, and it’s crucial to find the right knob position that provides max juice without forcing the engine to stall. Jimbo did exactly that and was able to successfully repeat launches from a standstill.

Even though this is far from a high-performance powertrain, Jimbo estimates it can support a driver and a passenger or about 300 pounds of payload in addition to the obviously required operator. And in his testing, he saw 40 miles per gallon! That’s pretty darn good if you ask me.

This is simply version 1.0 of what will soon become a more refined package. It shows all you absolutely need to resurrect a dead electric cart, though, and what a great place to start. Jimbo says he’ll soon swap it into a two-owner Club Car that’s been sitting in storage for the last 10 years. It’s nice, it’s red, and soon, it’ll be ready to roll out of the shed with its new petroleum battery powertrain—or, as I like to call it, the Harbor Freight hybrid.

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