Old Bolt, new tricks: Making an EV into a backup power station with an inverter – Ars Technica
Using a custom kit to make a budget EV offer some emergency power.
Back when EV enthusiasm was higher, there were fits and starts of vehicle-to-home concepts and products. If EVs and their ginormous batteries are expensive, resource-intensive purchases, the thinking went, maybe we should get something more out of them than just groceries and school pick-ups. Maybe we could find other things for that huge battery to do during the 95 percent of time it spends parked in or near our homes.An EV powering your whole home, or even pushing power back to the grid, is something higher-end EVs might do at some point with some utilities. I have a Chevy Bolt, an EV that does not have even a three-prong 110 V plug on it, let alone power-your-home potential. If I wanted to keep the essentials running during an outage, it seemed like I needed to buy a fuel-based generator—or one of those big portable power stations.Or so I thought, until I came across inverter kits. Inverters take the direct current available from your vehicle’s 12V battery—the lead-acid brick inside almost every car—and turns it into alternating current suitable for standard plugs. Inverters designed for car batteries have been around a long time, opening up both novel and emergency uses. The catch is that you have to start the car’s gas engine often enough to keep the battery charged.What’s different about this Bolt-specific kit is that the inverter pulls power from the 12 V battery, which in turn pulls from the car’s larger battery, the high-voltage one that makes it actually drive. And given that it’s an EV without emissions, it’s OK to keep it running in the garage. It’s by no means a whole-home solution—my kit maker, EV Extend, recommends drawing just 1,000 watts of continuous power so as not to drain the battery too far or damage the electronics. But it’s certainly better than having only flashlights, USB battery packs, and the power utility’s website open on your phone.What can you do with 1,000 W, plus a bit of “surge” overhead for devices that kick on strong, like a refrigerator? I can’t run my home’s central HVAC system, so an outage in the depths of a DC summer, or the occasionally painful winter, would still be unpleasant. There are only three receptacles, and they’re inside the car hood, so everything that needs power has to be reached by extension cord (and you don’t want to go too far with those). The car is also unlocked and running, with its key fob nearby, so it can’t be left alone.But for backup power I never planned to have, in an area where outages are less frequent, I have something like minimum viable backup power. With properly rated extension cords, I could run fans, a small space heater, or a single-room-sized window A/C unit for a day or two on conservative settings. I could, if my fiber provider is still up, keep the Internet and router running. At a minimum, I could keep a lot of distraction devices running with the Bolt’s 64–66 kW battery (assuming I fully charged it before an outage).I have not had a chance to really test this inverter, as the residential power in Washington, DC, has been stubbornly reliable since I bought it. But I did run it for about an hour mid-day to try out some of my assumptions.I bought a $444 kit from EV Extend, which specializes in inverter packages for the non-flashy and early adopter EVs: Chevy Bolts and Volts and Nissan Leafs. I opted for a 1,500 W pure sinewave inverter, capable of briefly handling surges of up to 3,000 W. The inverter itself is a commodity, and you can find it lots of places. The things I was really buying with this kit were:The owner of EV Extend makes a point of not offering his instruction manuals publicly. This is in part for “low-volume niche market” reasons. But it’s also because of a real concern that folks will see EV Extend setups, do some “I could rig that together” thinking, and expose themselves to a whole bunch of electrical, mechanical, or safety problems. He’s not opposed to DIY-ers, he writes, so much as he’s concerned about wiring quality and bad assumptions.From the images on EV Extend’s site and various Reddit installs, you can get the gist. A big brick of an inverter, with two thick cables running to a gray connector, and another connector plug running out from the 12 V battery area, easily tucked away (with velcro) when not in use. You can buy more or less surge protection, opt to skip pure sinewave inversion (not a great idea if you’re powering electronics), or upgrade and get a remote switch. But they are all largely the same.Among the frequently asked questions on the product page is “will this void my warranty?”The answer: No, it should not, because the Magnuson-Moss Warranty Act still exists, so there needs to be proof that this damaged your 12 V system. But there is also the unwritten caveat that it can still be very painful if your car maker or dealer is not up on their consumer rights laws.My installation took about 20 minutes. It involved some socket-wrenching, and I had to saw off an inconvenient but inessential plastic bit. The toughest part involved fishing some stiff, thick wire through a space between the coolant tank and a metal bracket (which the manual warned about).That night, I connected the inverter, turned on the Bolt, flipped on the inverter, and plugged in a USB-C wall plug. I connected an iPad, it started charging, and I felt a weird sense of accomplishment at having found one of the most expensive and inefficient ways to watch YouTube. For a few hours, I held some project-completing pride.Later that night, the myChevrolet app flung about a dozen notifications at me. The gist: Every single system on the Bolt was failing, I needed to have it towed to a dealer, and I was wrong to try and redistribute its precious electrons. These were bad messages to receive in the middle of brushing my teeth, and sleep did not come easy.Why the panic? The majority of EVs, however sophisticated, are heavily dependent on their old-fashioned 12 V batteries. This is due in part to how many of an EV’s ancillaries—locks, lights, infotainment, power steering, and more—are designed to run at 12 V, in common with the rest of the auto industry. But it’s also because when an EV’s higher-voltage traction battery is off, it needs to be fully off and de-energized, and the 12 V helps switch it off and keep residual systems running (Inside EVs has a good explainer on this). Disconnecting my 12 V battery, even for just a minute to attach a connector, gave the car fits about lacking this crucial reserve of juice.It’s weird, and it can be quite frustrating in the wrong circumstances. But the next morning, I started the Bolt, let it idle for a few minutes, and all the divinations of doom disappeared from the Chevy app. Six months later, I have yet to see any others. I’ve taken my car in for a general check-up since, and the mechanic made no note of my velcro-anchored connector.The inverter hook-ups were set, but household power remained stubbornly stable for months, so I decided to stage a pretend outage. Could the Bolt keep me and my wife reasonably comfortable in my office, the next room over from the garage? Could I keep a space heater or window air conditioning unit running, with occasional kick-on surges? What about the fridge? And how annoying would it be to have the car running in neutral in my garage the whole time?Here’s what I figured could fit into 1,000 W from the inverter and its three outlets, using appropriately sized and rated extension cords:I unplugged the Bolt, opened the hood, placed the inverter on a reasonably flat part of the compartment (next time, I will have a flat piece of wood to place there), turned on the car, and flipped on the inverter. So far, so good!Because the car was in park, it would automatically shut itself off after two hours. A number of committed campers and preppers on Reddit have suggested putting the car in neutral, engaging the parking brake (or putting chocks behind the rear wheels), and exiting the car from the passenger side (as opening the driver side door can make the car auto-shift for safety). Because it’s not in park at a low speed, the Bolt will make a whirring noise for pedestrian safety. I could temporarily cancel it by pulling the right fuse from the engine compartment box, so long as I left a note for myself with big letters to put it back in.I first plugged in my desk and all its accompaniments, then nudged and woke up my laptop and monitor: 14.7 watts. That seemed a bit low, given that monitors are typically more than 20 watts, but the inverter is perhaps slow to report the full draw. Still, there was lots of headroom remaining.Adding in the fiber-optic modem, the Dream Machine Pro router (specified at a 50 W maximum power draw), and its PoE-based devices boosted the number to 90 watts. That left 910 watts, which felt like a lot until I plugged in the big space heater and set it to its lowest setting. Once the heater had been on for a bit, I was at 850–860 watts, combined with the other gear. I knew space heaters were inefficient in a broad sense, but now that fact is burned into my brain in little red digits.All these things ran off the inverter for about 30 minutes (I wrote the previous two paragraphs with mostly inverter power), floating between 810 and 920 watts, and I saw the car’s projected mileage dip one mile when I checked on it. If I had the Bolt fully charged, I might get a maximum of 60 hours of this, or 48 hours at my typical 80 percent charge, give or take some resistance and use variables. Given what I learned, I would need to use a smaller space heater or very light air conditioning if I also wanted to keep the fridge running without nervous monitoring (and make up for some loss to an extension cord). That, or hope the power only goes out during comfortable temperatures.But I’m using the Bolt and inverter as a just-in-case option, not something I would lean on if regular multi-day outages were occurring. It would also be quite useful for car camping, though I can’t speak to that personally. The process has, like most DIY projects, taught me some things: about power draw, EVs, and my priorities. If you have a similarly nifty but not exactly new EV, consider checking out your inversion options for it—after you fully understand the limits and know-how required.This post was updated at 10:30 a.m. Eastern on March 17 to clean up references to inversion, which the non-engineer author regrets for their initial fuzziness. “Plugs” and “receptacles” were also better distinguished.Ars Technica has been separating the signal from
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