Anyone work on EV chargers? Other than cable damage or mechanical damage to the plugs, there are no moving parts. So what specifically inside is likely to stop functioning or needs regular repairs/replacement/maintenance?
I recently build my own a level 2 EV charger from an OpenEVSE kit. The heart of the charger is a big mechanical relay, which connects and disconnects the charging cable based on whether a car is connected. To control the relay, there is a small circuit board that communicates with the car, and also provides over-current, over-temperature, and GFCI monitoring. If any of these things go wrong, the relay will not close and the car will not charge.
The DC fast chargers include similar safety features, in addition to a big AC-DC converter. The DC power supply puts out several hundred amps at whatever voltage the car requests (usually 300V, but sometimes much higher). Normally, currents this high would require super thick & heavy cables, but DC fast chargers often avoid this using water cooling and active temperature monitoring in the cable. As the cable heats up from the excessive current, the charging equipment actively throttles the charging session to keep things from melting.
So yeah, there are a few mechanical things that can go wrong.
To deal with the high current on such relatively high (keyword here: relatively) gauge wire there's also massive active cooling involve. This adds even more to the complexity.
Heat. Your typical 150kW fast charging is like 3 houses with 200A service all maxed out. Or 25 houses running at typical load. If you want to convert it from 240V AC to 340-360V DC (actual voltage goes up as the battery charges), you will need a massive cooling system. For a quick perspective, imagine 1500 laptop chargers working all at once!
Getting it into the vehicle is another thing. 150kW at 360V is about 400A - twice what a modern detached house gets. That needs to get into the vehicle through a relatively flexible cable with a connector. IIRC, that requires an active cooling system (i.e. water loop) inside the cable itself, and the connector will still go through massive temperature swings. So you need materials that can insulate against 400V, bend well, and not crack when you repeatedly heat and cool them several times a day.
Oh, and many chargers [0] don't actually have a 150A or whatever connection to the grid, and instead use internal batteries that load up when nobody is charging, and quickly empty into your car once you pullup to it. That's another cooling loop, extra sensors, and possibly, a heating system, if you want to operate in winter conditions.
