Announcing the J1772 Hydra

[nsayer]

Ever want to charge 2 cars with one EVSE? Know how to solder? Then why not build yourself a Hydra?

I got into OpenEVSE a few months ago, and where I work we have a bunch of 30A L2 chargers, but way too many Volts and Leafs that only charge at 3 kW (yes, 2013 Leafs are starting to appear with 7 kW chargers, but they're in the minority).

We have a CHAdeMO, but it's not popular, for reasons inexplicable to me. So to solve this, I designed and built the Hydra. It has a J1772 inlet and two cord/plug sets. It intelligently divides the ampacity of the source EVSE between the two cars until one finishes, whereupon the remaining car gets full power.

I'll be at the Google event this weekend and I'll bring the Hydra with me. I'll be happy to demo it to anyone interested. And I suspect the chargers there will be occupied enough that sharing one will be particularly useful.

Anyway, the 1.0 hardware version of the Hydra is now available. The design and firmware have been field-proven with a variety of EVs and PHEVs. The J1772 components are the most expensive part of the BOM, but if you can get past that, the rest is cheap and easy.

Check it out here: https://code.google.com/p/open-evse/wiki/Hydra" onclick="window.open(this.href);return false;

 

[timhebb]

Gotta ask: what workplace installs and hosts a CHAdeMO for its employees? That is one over-the-top extravagant perk!

I'm thinking: an electric utility, as they are the only entities down here in LaLa land that have taken that step, other than Nissan dealerships and Mitsubishi, as far as I know.

 

[Deleted member 9549]

Commenting on the description on google, FYI: most 2013 Leafs can charge at 30A (6.6kw). Many do not have CHAdeMO, its an option.

 

[nsayer]

Gotta ask: what workplace installs and hosts a CHAdeMO for its employees? That is one over-the-top extravagant perk!

I'm thinking: an electric utility, as they are the only entities down here in LaLa land that have taken that step, other than Nissan dealerships and Mitsubishi, as far as I know.

Almost. I work at a company that is a utility company supplier. We make the Smart Grid smart.

 

[nsayer]

Commenting on the description on google, FYI: most 2013 Leafs can charge at 30A (6.6kw). Many do not have CHAdeMO, its an option.

Still, most of the Leafs I see where I work are older models. And most of them (again, given my available sample) are CHAdeMO ready. I think people (needlessly, from what I hear) fear the quick charger's potential impact on battery longevity.

From my (perhaps slightly selfish) perspective, it's mystifying to me that so many folks choose to occupy an L2 charger for 4 hours instead of the CHAdeMO for 15 minutes when they know how oversubscribed our chargers are.

Rather than fight the political battle, I chose a technological remedy.

 

[DaveEV]

This is a great idea to get two plugs onto a single charging station!

It's like an adapter that converts any EVSE into a ChargePoint CT4000!

Got any pics?

Oh - and for fun - have you tried splitting a J1772 cord twice? Then you get 3 plugs - though if you use all 3 plugs at the same time the double split ones will only get ~7A! Could be useful for when your stations at work really fill up - even 7A would be plenty for typical 8-hour work-day charging, especially for PHEVs.

 

[nsayer]

Got any pics?

I have a sort of crappy YouTube video... http://www.youtube.com/watch?v=bX33EAvZMNs" onclick="window.open(this.href);return false;

Oh - and for fun - have you tried splitting a J1772 cord twice? Then you get 3 plugs - though if you use all 3 plugs at the same time the double split ones will only get ~7A! Could be useful for when your stations at work really fill up - even 7A would be plenty for typical 8-hour work-day charging, especially for PHEVs.

I've only built one - they're kind of expensive - but if we had more than one we'd probably not daisy chain them, but instead use them on adjacent EVSEs - turning two plugs into four instead of one into three (though the net is the same, it's maybe a little more fair to have 4 15A plugs than a 30, a 15 and two 7.5s).

 

[DaveEV]

Got any pics?

I have a sort of crappy YouTube video...
[youtube]http://www.youtube.com/watch?v=bX33EAvZMNs[/youtube]

Thanks, found that one last night (embedded above now).

I've only built one - they're kind of expensive - but if we had more than one we'd probably not daisy chain them, but instead use them on adjacent EVSEs - turning two plugs into four instead of one into three (though the net is the same, it's maybe a little more fair to have 4 15A plugs than a 30, a 15 and two 7.5s).

Yes definitely, was just wondering if it'd been tried - could be useful in cases where J1772 plugs are in very short supply and you have cars that don't need a lot of energy.

 

[nsayer]

Yes definitely, was just wondering if it'd been tried - could be useful in cases where J1772 plugs are in very short supply and you have cars that don't need a lot of energy.

In principle, it should work. At that point, you'd be better off using a 16A L1 charger, though (as you point out, though, that may not be possible in public). One guy experimented with low pilots via OpenEVSE, and his BMW refused to charge with a 6A pilot, so some cars may be finicky.

You can't divide it further than that, since the minimum current the specification allows is 6A, so the Hydra refuses to start if it sees less than 12A.

 

[davewill]

Very cool! I assume the same basic design could be adapted to use a standard 240v plug for the input, but give the same sharing capability. It would be very handy for someone who wants to add a second EV or PHEV at home, but doesn't really want to run a second circuit.

 

[nsayer]

Very cool! I assume the same basic design could be adapted to use a standard 240v plug for the input, but give the same sharing capability. It would be very handy for someone who wants to add a second EV or PHEV at home, but doesn't really want to run a second circuit.

Yes. The Hydra firmware lacks a GUI or CLI at present, so you'd have to compile in the value of the "fake" pilot. Also, the Hydra lacks a GFCI, which is an important safety feature for an EVSE (since the Hydra plugs into an EVSE, it doesn't need it's own GFCI). In the end, I'm not sure whether adding dual output to OpenEVSE would be easier than adding GFCI and inlet current setting to the Hydra.

 

[GeekEV]

Hey, nsayer, I'll be there this weekend too. Look for the gray "SHOOOOM" Model S and say "hi"...

 

[nsayer]

I'll have a Honda Fit EV. I won't say I'll be the only one, but there can't be that many of us given that Honda's only sold a few hundred in the whole country so far...

 

[lemketron]

This looks awesome! I've been asking EVSE vendors to do something this for several years now, to eliminate the whole "charge rage" (and cable swapping / car moving issue that was the subject of a recent Mercury News article).

It sounds like you are in the Bay Area... Would you be interested in showing this off at a future SF BayLEAF meeting?

Have you considered doing a Kickstarter project to do a production run? Or maybe talk with the eMotorWerks folks to see if they might be willing to help productize it and/or merge it into a variation of their JuiceBox? That would be a great workplace solution to provide more J1772 cables with a limited number of ports.

A four or eight port unit would be great, too since everyone could plug in when they arrive and just leave their cars charging all day long.

 

[nsayer]

I've contemplated giving a presentation on it... I certainly wouldn't mind - quite the contrary.

As for a multi-headed Hydra, that's generally doable, but the present architecture uses an ATMega328P. It needs two analog ports per car and it needs i2c, so that uses up the 6 available analog inputs on that chip.

It's conceivable that you could use a multi-master system with a microcontroller per car all negotiating over a common bus, but that's a more expensive solution I haven't considered presently (it's certainly possible - a "car master" would probably be doable with an ATTiny84 (the 85 doesn't *quite* have enough pins), and in principle another ATTiny (or perhaps an ATMega) could master them all.

What it boils down to is that an unplugged car *cannot* charge, but a plugged in car *need not* be charging (or may be charging at a reduced amperage). What would be ideal would be to have lots and lots of plugs and a scheduling system, the gist of which is a request of "I need to get *this* much power by *this* time" and a response of "yes" or "no" or potentially a differentiated price.

 

[nsayer]

I have a new design for the board I'm readying at the moment.

It's the same as the v2.2 board, but replaces the inlet proximity and pilot handling circuitry with a GFI and a clock chip. With that, and with firmware changes, that turns the Hydra into a straight-up two-headed EVSE rather than something you plug a charging station into.

So far, I've only sold two Hydra boards. Would this variant make anyone more inclined to want to build one?

 

[Devin]

I have a new design for the board I'm readying at the moment.

It's the same as the v2.2 board, but replaces the inlet proximity and pilot handling circuitry with a GFI and a clock chip. With that, and with firmware changes, that turns the Hydra into a straight-up two-headed EVSE rather than something you plug a charging station into.

So far, I've only sold two Hydra boards. Would this variant make anyone more inclined to want to build one?

That would make me more interested. Still a bit on the nervous side but would like to replace our 3.3 and 7.2kW EVSEs with something that can dynamically supply both the RAV4 and the Focus with greater power. I could see doing this as a summer project once this semester is over.

 

[nsayer]

Still a bit on the nervous side but would like to replace our 3.3 and 7.2kW EVSEs with something that can dynamically supply both the RAV4 and the Focus with greater power. I could see doing this as a summer project once this semester is over.

The board itself is agnostic as to the inlet and outlet power. You'd set the capacity of your supply and the rating of the plugs (input and output current). The Hydra will insure that the output pilot for one car never exceeds the output current, and that the two added together never exceeds the input current. As long as your relays have 12 VDC coils (or you use a small driver relay to drive a contactor), there's no reason you couldn't have a dual 80A Hydra as long as the high current paths are designed for it (I can't imagine the wire gauge you'd need for a 160A supply, never mind the fact that you'd need a 200A breaker, which is what our whole house has presently).

I specify 30A relays in the reference design, which isn't going to max out a Rav 4, but if you can find beefier parts, you should be fine. If you've got a 50A breaker, and can get 40A relays and J1772 cable/plug assemblies, that would probably be ideal - 40A for one car by itself, or both cars at 20A.

 

[Devin]

Still a bit on the nervous side but would like to replace our 3.3 and 7.2kW EVSEs with something that can dynamically supply both the RAV4 and the Focus with greater power. I could see doing this as a summer project once this semester is over.

The board itself is agnostic as to the inlet and outlet power. You'd set the capacity of your supply and the rating of the plugs (input and output current). The Hydra will insure that the output pilot for one car never exceeds the output current, and that the two added together never exceeds the input current. As long as your relays have 12 VDC coils (or you use a small driver relay to drive a contactor), there's no reason you couldn't have a dual 80A Hydra as long as the high current paths are designed for it (I can't imagine the wire gauge you'd need for a 160A supply, never mind the fact that you'd need a 200A breaker, which is what our whole house has presently).

I specify 30A relays in the reference design, which isn't going to max out a Rav 4, but if you can find beefier parts, you should be fine. If you've got a 50A breaker, and can get 40A relays and J1772 cable/plug assemblies, that would probably be ideal - 40A for one car by itself, or both cars at 20A.

I actually have a 60A breaker (currently split to 20 & 40) right now. The Hydra would eliminate the need for the split and I could supply up to 40A per vehicle with a ~48A combined limit. Would it be easy enough for me to set it up with those parameters or am I getting too complicated for my own good?

 

[nsayer]

I actually have a 60A breaker (currently split to 20 & 40) right now. The Hydra would eliminate the need for the split and I could supply up to 40A per vehicle with a ~48A combined limit. Would it be easy enough for me to set it up with those parameters or am I getting too complicated for my own good?

You're right about the 48A combined limit, but there's no particular reason you can't achieve the 48A per vehicle as well, as long as you get contactors and J1772 cables and plugs that are up to it.

The NEC says that for a 60A circuit you're going to need to run AWG 4 copper wire. If you don't have that in place already, that'll be a necessary prerequisite. You'll need to run that all the way into the bus module inside the Hydra (that's no problem, though. A Cooper-Bussman 16220-2 is what I specify, and it can go all the way to AWG 4 on the load side and 2/0 on the line side). On the line side, I believe AWG 8 would be enough to go from the bus module to the contactors, and then the other side of the contactors would be attached directly to your J1772 cables.

Getting 50A rated contactors is the next step, and if they don't have a 12VDC coil, then you'll need pilot relays to drive them.