Plug Bug: Killing Chargepoint Charging Stations

Electric Bug

Well, my bug wasn’t killing the charging stations, but it was giving them an internal error. It seems that the newer charge point stations with a large display weren’t compatible with my car’s J1772 port for some reason. There are rows of them at my work, and I’d plug in and it would give an error: 

IMG 2387

Error Code #303-RSC, RELAY STUCK CLOSED. I couldn’t find any information on this error, and both phone calls and emails to ChargePoint went unanswered. The phone people just assumed it was a problem with the station, but I told them my car caused it and I wanted to know WHY it happened. Still, no info.

So, I really wanted to use the closer chargers at Infinite Loop instead of walking across the street to the older style. I started poking around and discovered the two pins were leaking voltage to ground. The ground is the 12v ground of the car, and I had known about a ground leak for quite a while. Pack voltage is usually isolated from the car’s normal ground system and chassis. On cars, the chassis is used for the 12v negative side (the ground). Yet, if I compared the plus side of an amp meter to my negative most terminal on my pack, I would read almost my entire pack voltage!

I knew this. It went away when I unplugged the controller/motor, and I assumed it was the brushes in the motor and not a big deal. Sometimes dust builds up in the brushes and causes a leak (or so I’ve heard). 

I figured this might be causing the charging station issue. It was easy to test; I drove to work, unplugged my controller/motor (it is on a BIG anderson connector), and sure enough — it worked!

When I got home I had to figure out where it was leaking. If I disconnected just the motor the leak still happened. I finally traced it to the controller. The Netgain controller has two high voltage “pre charge” wires. They are orange wires from the controller. They go to the contactor that the controller controls. One goes to the pack voltage side, and the other goes to the other side of the contactor that is “on” when the contactor is closed (providing power to the controller). The controller does some type of voltage check on both sides to pre-recharge things.  For some reason, the side on the non-open side of the contactor caused the problem; disconnecting it fixed the problem — well, almost, as the leak was only 2 volts or so. It was leaking “out” for some reason from here, and it is some problem in the controller. Swapping the orange wires didn’t matter (they were interchangeable). If I removed the pack voltage side wire, then of course, the leak went away entirely.

So, I was hoping I could put this pack voltage wire on a relay that comes on only when the key is on. This way, the charger works when the key is off.

I found a good relay on DigiKey and Mouser, and a better price on Amazon (especially with free Amazon prime shipping):

This is an Omron MKS1XT-10 DC12 relay. The details on Amazon are poor, and Mouser’s specs stated: 10 amp contact current (more than enough for that wire thickness), 220 VDC switching voltage (my pack is 154V nominal, and way less than 200V ever), and the relay runs of 12VDC (or 24VDC). Perfect! Amazon says $20 now…but it was $26 when I bought it (d’oh!)

I also got a terminal mount for it, so I could easily mount it in the car:




 So, for about $40 I’d be good to go! I got them, tested it, mounted it in the car, and the car’s controller still worked when I was doing this switch. I was afraid the controller might pre-charge on key-on *BEFORE* the relay kicked power to it, but it seems to work okay.

And, now it works at the charging station without having to unplug the main battery pack. Excellent!



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