The J1772 Hydra Helps You Charge Two EVs At Once

There are plenty of electric vehicle (EV) chargers out there that are underutilized. This is particularly common where older EVs are involved, where the cars may only be able to charge at a few kW despite the charger being capable of delivering more. [Nick Sayer] regularly found 6.6 kW chargers being used by vehicles that could only draw down 3.3 kW at his work. Thus, he built the J1772 Hydra as a nifty double-adapter to charge two cars at once.

The Hydra comes in two versions. One is a “splitter,” which is designed to be plugged into an existing J1772 AC charger. The other is a version designed for permanent installation to an AC power supply as an EV charger in its own right. Either way, both versions of the Hydra work the same way. In “shared” mode, the Hydra splits the available AC power equally between both cars connected to the charger. When one completes, the other gets full power. Alternatively, it can be set up in “sequential” mode, allowing one car to first charge, then the other. This is great when you have two cars to charge overnight and don’t want to wake up to shift the plugs around.

It’s a neat hack that could be useful if you’re running older EVs that rely on slower AC charging. We’ve seen other DIY EV chargers before, too. Expect hacking in these areas to become more commonplace as EVs grow in popularity.

15 thoughts on “The J1772 Hydra Helps You Charge Two EVs At Once

      1. Why the derision for people that speak Sarcasm as their mother-tongue? For some of us, it’s only on good days that we can be bothered with markup to help you straight-speakers along. …

        … …/s

    1. Early EVs were marketed and sold as if ICE vehicles didn’t exist. Rather than acknowledging their shortcomings compared to ICE and responding, they competed against themselves with varying trim levels that offered different charging speeds.

      The Leaf SV was decidedly better than a Leaf S, but in reality the differences were small and both suck compared to an ICE. Full disclosure, I have a Leaf SV and it’s a decent little runabout.

  1. I was expecting a switching method, car A for half an hour, car B for half an hour, etc, making sure that both vehicles receive as much of a charge over night as they could while being fair. (Advantageous if you have a better rate at night, and concerns over 1 car being charged at the detriment of the other).

    1. “Hey charger, tomorrow I am leaving for work an hour earlier than usual and my wife is going to visit her mother in the afternoon. Can you please make sure both cars are properly charged?”

    2. I know that’s how the Chargepoint stations I installed a few years ago (could) work. It was a while ago but iirc you could set it depending on if it was fed by an 80 or a 40 amp breaker. With two cords on 80 it would feed both cars a steady 40 but if all it had was a 40 it would switch back and forth between both cars at 40 amps. I don’t remember the duty cycle but I’d imagine it was shorter than a half hour but I’m not sure.

    1. One possibility is that there is only one charger in a place where installing a additional charger means convincing someone stubborn, aka you don’t own the place.
      Another possibility is that this is done for the fun of it like many of the things we see here, aka look what I have done, isn’t it cool.

  2. EVs are all about BG GUBBMNT CTRL of US! Where U can go – Wen U cn go – How oftn you cn go – Hw much it $$ to go – Why RU going? Et-Cetera… All is TRACKD. Forcin’ EVs on all peeps meens THEY PWN us ALL. One chg point per EV meens ALL EVs are under central/collective GUBBMNT CTRL. U-Must Embrace-It, Accept-It… OK Com-Rad? [Yea U hv NO choice.]

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