Good project with little to no alternatives at the moment
For J1772 Hydra
If you have two electric cars, you need something like this to lead a normal life.
By the moment of this writing, i have been using Hydra to charge my cars for 3.5 months, and i am as happy as can be.
There are not many options in that case. The simplest one is to install 2 chargers on 2 breakers. That might not be possible (as it was not for me), as it adds to loads on the panel -- one may run out of capacity both amperage and space wise.
Then, one might try and find dual head chargers on one breaker. Not many at all as far as residential options are concerned, and they all cost a little fortune (we are getting into double digits of a percentage of the car cost itself!). Given the standards seem to move pretty fast, this does not look like a good expense at all.
And there are absolutely none that one could just plug in.
Hydra has it all -- and it does it in a very compact package. Ability to run shared and sequential modes in residential settings are superb and are exactly what one needs to keep things running smoothly. TOU scheduling is present (I actually extended it to 5 events to accomodate half-peak options of my tariff).
There are a few things that add to the cost though:
(a) one needs to be ready to mess with the assembly process. This requires time, tools, and some experience. That said, if you build your own computers like I do, this should not be a great problem (assuming the process of assembly is well understood).
(b) Bill of materials could be better. There are less expensive alternatives and suppliers on the list. Some little things might be mentioned (like e.g. hanging tabs for the poly case -- if you don't order them at the same time, that's 2x shipping charge on a separate order for a very small accessory). Packard contactors @ open evse store can be used, but i ended up using these ones (they were @ $9 apiece at Amazon at that time) -- they are also compatible: https://www.amazon.com/gp/product/B01J4Z8SZU. I bought a lot from amazon; but mounting hardware seems to be better bought @ digikey, along with a few other components.
(c) There may be a few bugs.
The PCBs by OshPark are not QA'd, i had a missing path on mine, which was not obvious until i went back to Nick to analyze it. Luckily, I lived not so far from him. Otherwise, it would've been pretty hard to figure out if it was my mistake or faulty PCB's or something entirely else. I don't have necessary expertise for this kind of trouble shooting. Sequential mode was broken in the latest firmware, i had to fix it and a few other things, i PR'd the updates to Nick's github.
(d) Documentation was generally easy to follow, but I see how first time experience may lead to a wiring error, which is especially something you don't want to do with the HV componentry.
(e) Design: there are limitations. Two major features that are missing in comparison to modern EVSEs are wifi with cloud analytics (or a phone app of the same), and temperature throttling. I do not care much for the analytics (my Tesla app is going to tell me everything i need to know), but the temperature throttling is an important monitoring and safety feature IMO. Open EVSE has been having it for years now; so is the L1 EVSE that came with my car. I am planning to implement temperature throttling addition to the firmware as soon as i get a Hydra version with an I2C header to connect one of the cheaper sensors found on Amazon. That should be easy enough. I found that a spurious false ground fault error may occur that would prevent cars from completing the charge process. Open EVSE apparently has this issue too, so they added a feature that would automatically attempt to restart the charging up to 4 times. I added that feature, among a few others, in the latest Hydra patch as well.
Conclusion: this is an excellent design, customizable as well, but one should be keenly aware that like all DIY projects, this is not exactly a plug-and-play project.
