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Comment by londons_explore | Hacker News Reader

Every time I see a 'charger' like this I'm disappointed.

This isn't a charger. It is a fancy electrical junction box. The voltage into the box and the voltage out is the same. The only function of the box is to switch the power on and off. And the car already has a switch in to switch stuff on and off anyway. So this box of expensive electronics is entirely redundant.

And they don't even provide much power - typically 32 Amps at 230 volts. Ie. about the same as a caravan hookup. But a caravan hookup doesn't need to run Linux...

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> The only function of the box is to switch the power on and off

That is false. These are much more sophisticated than a mere relay. Sure, there is basic logic between vehicles and EVSEs which is basically a smart relay: https://en.wikipedia.org/wiki/SAE_J1772#Signaling

...but the electronics you mentioned are for onboard controls (energy monitoring, Time of Use enforcement, load balancing between multiple units, etc). Some EVSEs are very simple, but many -- including the one in the article -- also handle upstream communication like OCPP: https://en.wikipedia.org/wiki/Open_Charge_Point_Protocol https://www.chargepoint.com/files/OCPP-Fact-Sheet.pdf

Here is an example of integrations for the model in the article: https://zaptec.com/downloads/ZapChargerPro_Integration.pdf

There are also implementations of power line communication over the Control Pilot pin in J1772, which most people notice when charging via CCS at a DC Fast Charger, but that is not limited to L3 charging. Note that QCA7005 chip in the article: https://www.qualcomm.com/products/application/wireless-netwo...

See also: Plug and Charge https://en.wikipedia.org/wiki/ISO_15118

It’s a safety system, a billing system, and possibly a coordination system to avoid overloading an upstream circuit. Also it’s a special fancy outlet that tells the load how much current it may use.

There’s a nice open source implementation called OpenEVSE.

>Also it’s a special fancy outlet that tells the load how much current it may use.

Isn't that the sort of thing that can typically be accomplished with nothing more than a resistor or two?

It's based on a square wave duty cycle, so you'd need something more like a '555. But yes, J1772 is designed to be dead simple and cheap to implement.

By the time you implement the rest of the protocol, you might as well have an actual microcontroller, at which point you don’t need the 555.

(Please don’t build an EVSE without the big relay and its associated safety controls. No one needs an outdoor cable supplying ~240V pin-to-pin that’s live while you hold it on a rainy day.)

Simple resistor signaling wouldn’t work for current sharing; two EVSEs with a single 40A supply [32A continuous] can advertise 32A if only one is in use and switch to 16A if both are in use. (Same concept extends to a larger pool of EVSEs which can limit to a max total current across the pool.)

Ah, okay, that is fancier than just advertising a fixed max current.

Tesla's Mobile connector supports different pigtails for the input circuit. That way it can support anything from a regular outlet (NEMA 5-15) up to something more common for an electric range (14-50).

The mobile connector detects which one based upon resistance.

As others have mentioned, this is often too simple for EVSE to Vehicle connections, as that might require the power level to be dynamic. Load sharing, limitations in supply capacity, or heat may all be potential reasons to limit available power.

Not only can you coordinate several chargers (if you are in a shared garage), but you could also coordinate usage across other devices connected to the same residential fuse box (all such in Norway has a HAN interface); for instance you could restrict the charge to the car when the dishwasher is running. (Sadly, the IEC 62196 control pilot pin seems to be a very primitive system).

"Charger" is a colloquial term. Technically this is Electric Vehicle Supply Equipment (EVSE). You're right that it (usually) doesn't do anything in terms of voltage regulation, but that doesn't mean it doesn't serve a useful purpose (as others in this thread have outlined).

> And they don't even provide much power

Typical caravan hookup here is single phase, 230V, 16A. This is ~3.5kW. Typical EVSE is 3-phase and 32A — ~22kW. That is fast enought for fully charging an EV overnight/during a working day. In fact there are plenty of EVs where AC charging is limited to 11kW. This is not a roadside fast DC charger, the application is quite different. Statistically most people charge less than 20kWh to get to the full battery in such scenarios.

You're correct it's an EVSE (EV Supply Equipment) not a "charger," but for all practical uses, the word choice doesn't really matter

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