Charge Your EV The Portable Way

[Andrew Rossignol] has a slightly unusual plug-in hybrid vehicle, a Cadillac ELR, and his latest project for the car sees him building a battery-powered portable mains charging pack for it in an attempt to increase its range. If this seems to be a rather cumbersome exercise, his write-up details the work he put in trying to hook up directly to the car’s internal battery, and how a 4 kW mains inverter and an off-the-shelf mains charging station were the most practical alternative.

His first impulse was to hook a second supply to the car’s high voltage bus from a supplementary battery pack and inverter, but in this aim he was thwarted by a protection diode and his not wanting to modify the car to bypass it. So the unlikely solution was to take his battery pack from a second-hand Toyota Prius upgrade kit and build it into a frame along with the inverter and charger. The result is something akin to a portable generator without the small gasoline engine, and while it is hardly the most efficient way to transfer energy from a wall socket into a car it does offer the ELR a significant range upgrade.

The cost involved has probably kept away many readers who would like to hack their hybrid cars, so we’ve seen surprisingly few. This home made Geo Metro supplements its forklift motor with a small gasoline generator. Meanwhile [Andrew] is no stranger to these pages, among the several times his work has appeared here are his rundown on OBD sniffing the ELR, and from a while back, displaying graphics on an oscilloscope including a Wrencher.

36 thoughts on “Charge Your EV The Portable Way

  1. Seems like to me that could be placed in a small trailer and towed behind in order to increase range for trips. That way it can be quickly disconnected given he is still using the external connector.

    If this went “mainstream” and an infrastructure existed, it could be swapped out faster than filling a SUV tanks with gas.

      1. Nice idea, and while the “Smart Hitch” is probably a vital part of the system, the pessimist in me wonders if it is too costly to be licensed as to prevent any auto or trailer manufacturer to be willing to adopt it.
        Sort of like IBM’s MicroChannel Architecture, or Sony’s Memory Stick…

    1. Interesting system. Wood seems a little bit not expected. Vinyl even maybe or Delrin?

      My original plan was to buy an all electric Ford Focus and integrate a Honda generator into the trunk or a lower drag swing open tail cargo box built into the rear like a tow package is mounted to extend range and provide the additional charge option. I even still have the BlackMax 8750W generator for future implementation… though am thinking more I don’t need that with the Prius and want more room and the kitchen/storage in the lower drag swing open tail section once I get around to completing. I still have to get the plug in charger components to make my 2013 Prius PHEV. I’ve also wanted to implement shutters on the intake grill in the front so to be able to open and close depending on outside temperature. Seems there is potential to lower drag a little on the underside also and pre-heating intake air also for cold weather operations probably with the same circuit for the grill to change intake ports (pre-heat or stock).

      1. This has actually been tried, at least with a Tesla that I know of. It may sound silly, but the car ended up getting 20mpg effective efficiency which is pretty impressive given the number of highly lossy conversions involved. It is comparable to the efficiency of other heavy luxury sedans.

        The onboard ELR generator is easily capable of 30mpg, and with the right driving style, 40mpg is not unobtainable so it is best to use the efficient onboard generator if gasoline is the only option. There is a mode in the Voltec powertrain that uses a clutch to drive the wheels mechanically when a rev match between engine RPM and wheel speed is made (typically in the 65mph range). This gives an added efficiency boost at high speed.

        They’re interesting cars.

          1. I always use EV or Economy mode in my Prius and I don’t like the cold weather affording only 44.5 mpg. Not great compared to capabilities. I assume with the mileage the battery will need to be replaced or upgraded since not a lithium ion battery. Would be nice if a new chemistry that is even more efficient came out to bring down the Li-Ion price.

            I was thinking adding faring’s on the side wheels also… forgot to note that. Though like the rear tail cargo container designed to lower drag on the rear end… would change the stock look… however has been done with an aftermarket package that has some other options like bullet style rear view mirrors that I’ve though can be improved on even more with cameras instead and LCD screens on the dash. Even better would be semi-transparent built into the front window.

            Seems when I looked into the 120V level one options… it wasn’t on the 2013 Prius 2 model. Needed a huge rectifier system from what I recall… though I might be thinking to output 120V from the 220V battery. I’ll have to look into again.

            I found a drawing I made back in 2015 or I’m thinking more like early 2016 and posted:
            https://www.facebook.com/photo.php?fbid=2872109916184125&set=a.1586822128046250&type=1&theater

            Still surprised there aren’t lower drag rear cargo containers on the market already. Thinking a swing open design with some sort of tent pole and canopy with a screen option for tailgating and camping out of. Seem if designed correct, will lower drag also to offset load reduced efficiency. Once this is paid for, I am going to modify more and probably invest in a U.S. brand PHEV or EV. I think an off road suspension package would be awesome as there is a “Pakistan” package I read about.

          2. For those of us with hybrids… we can add an extra gas tank (bring a gas tank with) as I’ve done that before to extend my range. Amazing how 6 gallons (more than a half tank), and even one gallon, can extend the trip range with these more efficient cars. Having cost effective hacked out mods to improve options and increase efficiency is neat too. The 120V option I was thinking about in the last comment was as an output to use the car as a generator basically. Looks like the PHEV options allows for 120V charging and isn’t that complex or large in volume. The rectifier to output 120V thought was if directly from the 220V battery and that is why I invested in the additional buffer batteries and charge controlling so I didn’t go past the 700W max say if tapping the stock car battery system with an inverter. I even hacked out one of the 1200W/2000W peak UPS’s with two marine switches and a 12V output/input so I could charge those batteries since the UPS is 24V DC battery input since that was my first thought for a system… though the capacity sucked to fast without external batteries.

        1. I’ve gotten 27 mpg in a Pontiac GTP with a 3800sc and 26 mpg with a Corvette and a 5.7 V8 of course this was on the highway.
          Both cars get terrible gas mileage in town though.

      2. I have considered that. Others have mentioned a conversion efficiency penalty, but I only make a few long-range trips per year, so it may be worth that. A properly designed system would be significantly better than the early attempt you mentioned.

        If the trailer combined storage (ie, trunk space) that could be something rented several times a year. Otherwise the EV could be used for commuting to work or local shopping.

        1. I imagine a rental lot on the outskirts of town where you can just drive ina and hook up, then drop it off on the outskirts of the city you are traveling to. The trailer could even be a massive battery that give you the range needed.

        1. Pretty much all trains that are not direct electric power from over line cables, or antique steam engine trains are diesel generators on wheels using electric traction motors to actually propel the train.

          Pretty much every diesel train out there can probably be retrofitted to being driven by overline electric power by simply adding a pantograph and switching gear

    2. At the risk of necromancing this comment thread, I’m surprised that everyone was fixated on electrical generation trailers and no one mentioned pusher trailers.

      It’s far more efficient and effective to put a gas tank and a small (like a motorcycle) engine with a driving wheel on the back of an EV. The supplemental gasoline engine is only responsible for maintaining level ground highway cruise and the EV’s normal propulsion system does everything else. The engine would become active when the vehicle’s cruise control was engaged. Tap the brakes and it switches back into neutral.

      As others have mentioned (in discussing generator trailers), given a perfect world, there would be no reason for anyone to actually *own* one – a universal interface would exist on all EVs and you would just rent one for a road trip.

  2. There’s a guy with a leaf who used a turbine engine, and a dcqc to build a charging trailer. If you google creatively you’ll find it.

    There’s also companies who sell extended packs that fit in the trunk well of the leaf. I’ve actually thought about buying one, but instead opted to sell my leaf, and buy a ice car. Canada isnt really ready for EV’s unless you can afford a tesla.

    1. Odd.
      A friend just South of Ottawa bought a Volt, then installed a charger at home powered by 240 VAC. Then he ditched the furnace and got an Air-Sourced Heat Pump and ditched the propane stove and went electric. He drives to/from work five days a week, round trip just under the Volt’s range. Summer it does it on electric only; winter sometimes using a bit of gas. His monthly electric bill, house & charging car, is less than what the monthly gas for his car used to be, and he won’t be buying propane anymore. With evening and weekend driving going beyond the Volt’s electric range, they’re spending ~$18 a month on gas for the Volt. Wishes they bought a Bolt, but they wanted the ‘on gas’ backup to always be able to get home.

    2. It really depends on the owners personal transportation needs. A LEAF like mine is the fastest car in the town when it comes to heating up after you turn it on. (faster than a Tesla or Bolt) That’s wonderfull. :-) It’s an older 24KWh model so I get ~70 Miles range in the winter, less if I work the heater hard, but If I worked only a couple dozen miles way from home, that’s no problem. Fifty miles from work?…nope, don’t try it. So it depends. I’m in the phase of life where I often visit the school four times a day moving my kids around to and from events. My LEAF is perfect for that, always warm, always perky, and handles well in the snow…but I live in a community of 10000 people, everything is relatively close. If the shoe fits, wear it. Otherwise…you might have to get creative or choose a completely different option.

      1. The Leaf uses a PTC heater and it’s AC in heat pump mode while the Bolt uses a Rube Goldberg setup that heats a coolant loop which then passes through a conventional heater core.
        Not sure why GM did things this way maybe so they can just throw the EV powertrain into what is essentially a Chevy Spark.
        The Tesla uses just a PTC heater less efficient than the Leaf’s combination heat pump resistance setup but they have huge batteries so it’s not a big problem.

  3. Disclaimer – I own and have extensive experience with a Chevy Volt, which if I understand correctly, is the same system.

    There are a ton of tradeoffs in electric car design – I’ve played with the numbers since I was a teen in the 60’s. More batteries can mean less range as they add weight, and not just battery weight – you need to add frame strength and so on or what you are really doing is deciding the original designer didn’t get it right (and you may now be violating various safety guidelines, more legal for you than for the manufacturer, but adding danger nonetheless).

    I charge my Volt off my solar array when there’s extra, which is often as it’s a huge array. It gets north of 40mpg when the battery is exhausted, which is a pretty good deal for what is a little hot rod at < 50 mph at least – corners like it's on rails. At 40+ mpg the cost of operation due to gasoline is nil and not even really worth improving. Even where I live – and it's a 26 mile round trip to the beer store – it manages most trips without the engine, and since 2012 I've used ~ 100 gallons of gasoline, while retaining all my luggage space. Even if the gas were high priced (pure high octane is worth it in this self-tuning ICE) – the best thing to do is realise the engineers were pretty good, tradeoffs are inevitable, and just drive the thing. In fact, at gm-volt.com pretty much all the early adopter were engineers who realize this and that the quality of the tradeoffs made here is excellent for the real world, though the purists may not be happy. They can design their own cars…and they'll find out.

    Bob Lutz, king of hot rods and tire smoke, shepherded this through GM. It's not a crap car, he's a real car guy. There's a really good Charlie Rose interview with him and Elon Musk that should be required viewing.

    I really doubt this amortizes decently. What has worked out well is using it as an adjunct to my house system. Extra kWH can go into the Volt (the home system "only" has 48kwh of batteries), and due to a simple cheap inverter I added to it's 12v system (which is charged with a 175 amp switcher off the main bank) I can also back up my home…it can be a generator that auto starts its own engine as needed and knows how to take itself to the gas station – I don't even have to deal with a jug…This is a last resort here as I have other backups, but frankly, only a very old and very polluting diesel here can make more power per gallon of fuel than the engine in the Volt, and it's not much more.

    1. I agree the Chevy Volt is a good car, but, it’s timing was wrong; in light of the Obama administration bailing out General Motors -shafting the stockholders but coddling the Union workers doing so. As a result, many people stopped buying any “Government Motors” vehicles, regardless of how good they may have been.

      1. What? This makes sense to you?

        What should have happened? If the govt let GM fail, no one would be buying GM cars, either. The stockholders would have lost their entire investments and the North American automotive supply chain would have been hit badly. There is a good chance that a bad recession would have turned into a worse depression.

        Or would you have preferred that the govt had bailed out the shareholders because, why? Or is all you care about shafting the unions because, well, why?

        You come across like a dumbshit who spends too much time listening to dumbshits on dumbshit talk radio.

    2. dcfusor ???? nice to know that you read about my project. I enjoyed cruising your website a while back.

      It amortizes quite poorly, but using it to shift some on peak loads here at $0.44/kWh helps. Needless to say, at these rates I charge at the office where it is free.

      The Chevy Volt is a super cool car and I think an important step in the electrification of the fleet. I convinced my father to buy a 2nd gen Volt and he has only put $10 worth of gasoline in it this year. That’s quite nice if you ask me.

  4. I remember seeing a Sunday comic as a child, it showed a car salesman talking to potential customer.
    In front of them is a car with a “trailer” and a driveshaft connecting the car and trailer.
    The salesman is saying, “You’ll never guess where they put the engine this year!”

  5. I think if I’d buy an electric or hybrid vehicle, I would want an option to supplementary charge it (albeit would take longer) through a standard 120 VAC 15 amp electrical outlet, because… they’re everywhere. Here in the North Country, a number of employers/landlords/motels supply 120 VAC outlets for “engine/tank heaters” in their parking lots, to allow cars/trucks to start easier in the winter. Or, if you’re staying overnight at a friend’s house you could use one of their outside outlets to give the batteries a little boost.

    1. “I think if I’d buy an electric or hybrid vehicle, I would want an option to supplementary charge it (albeit would take longer) through a standard 120 VAC 15 amp electrical outlet, because… they’re everywhere. Here in the North Country, a number of employers/landlords/motels supply 120 VAC outlets for “engine/tank heaters” in their parking lots, to allow cars/trucks to start easier in the winter. Or, if you’re staying overnight at a friend’s house you could use one of their outside outlets to give the batteries a little boost.”

      Actually, most EV’s easily support this. 115v @13 amps is called level 1 charging. 220 @30 amps is level 2 charging. Most EVSE’s (including the OpenEVSE he used) supports both over the normal J1772 charging cable.

      EVSE’s are pretty simple, pretty much just talk to the car and tell it how much voltage and current it can provide safely. Once the car accepts it flips a relay on. There’s also normally some extra GFCI stuff built-in to prevent shocks in wet conditions.

    2. I bought an EV recently and have been charging primarily via 120VAC/12A. My commute is 40 miles roundtrip, which takes about 8-12 hours of charge time.

      Subfreezing days reduce efficiency, so if I lived someplace like Canada, I’d need a 220VAC circuit.

    3. Toyota’s plug-in Prius and Nissan’s Leaf (I own both) each come with a cable that plugs into a standard 15 map US 120VAC outlet as standard equipment. It’s called level 1 charging.

      However, if you buy a plug-in hybrid or electric car, do NOT buy one that only has level charging capability. The Leaf takes 15 hours to charge on that cable! (Frankly the vendors should not even offer cars without higher capacity charging, it’s a huge disservice to the customer.)

      The better equipped models of Leaf can accept CHADEMO (level 3) and 240 VAC (level 2) charging. You need level 2, unless you are literally a little old lady who only drives her car once a week to church on Sunday.

      1. My 82 year old mother-in-law loves her leaf and charges with only level 1. Everyone else I know with an EV has level 2 charging at home.
        The 2018 LEAF includes a cord that allows charging from 120 or 240 volt power.

    4. I wouldn’t try to charge an EV from a block-heater outlet. Those are typically expected only to supply a relatively small load and an L1 EVSE is anywhere from 8 to 16 amps. Even if you have a 16A L1 EVSE (and that’s going to be problematic unless you can power it from a dedicated 20A circuit breaker. EVSEs are continuous duty devices that require derating the breaker 20%), that’s only about 1.9 kW. A typical home L2 EVSE (with a 40A circuit breaker) can supply more like 7.6 kW – quadruple the charging speed – and max out a typical (non-Tesla) EV’s AC charging system.

  6. So is it possible with or without modifications to essentially plug a leaf into a 220Vac cable and charge it whilst it’s driving?
    Imagine a cable hanging out the side going to a trailer with a generator fitted.
    Ignore that nissian dont rate the leaf for towing.

    Is it possible with the leaf or other EV’s to charge them as you drive, out of the factory ?

    1. For obvious reasons my Nissan LEAF has no interest in moving while charging. (high voltage cord yanking ain’t pretty) The interface designers regard moving and charging as mutually exclusive. You pretty well have to restart or shut-down the car to change from one mode to the other. That said, I don’t remember ever driving up to my charger, just putting it in park and then telling the car to pop open the charging hatch and plugging it in. I bet it won’t let me open that hatch while in “moving” mode and charging is a cooperative thing between the wall box computer and the car’s computer and I just don’t see the car playing along about charging while it is thinking about being in park, or drive, or reverse. At least with my unit, charging and being driven are separate modes. That doesn’t mean you can’t tap into the main high voltage power bank but that’s not an OEM thing. :-)

      1. Is the battery to motor “inverter” also being used for the charging circuits in some way.
        What you say is logical of course. There is probably a way around it that someone has found, if not after market charging solution.

        Dare you to jack up the front end and try to move whilst it’s plugged in:o)

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