I should add that he mentioned a problem with a previous repair and that the charge cable had not been reconnected properly.

 

My Coulomb CT500 has worked reliably since installed 10 years ago, but appears to have failed this weekend. The display screen is dark and green power light is flickering faintly. Tried resetting the circuit breakers but no change.

I was wondering if anyone out there is still repairing these units.

 

I too have a dead CT500 which I have several times considered tossing and have the same question as DZ1.

My replacement is this plug-ended Amazon Basics product https://smile.amazon.com/gp/product/B07HKW6JSY for which I paid a little less than $400 when it was first introduced about two years ago and has since been performing admirably.

I have a potential use for the CT500 in another location.

Thanks in advance.

KNS

 

I too have been greatly helped from this thread. Thank you to all who have contributed. My CT500 had the common melted black plastic connectors where the charge cable leads plugged in. I cut them off, replaced the 8" aluminum wire pigtails back to the relay with the same wire gauge but in copper. I have added photos, because there was a distinct lack of them in this thread.

 

I have 14 year old Coulomb CT-500 that has performed flawlessly, but recently started randomly shutting down while in idle mode (unplugged from car or waiting to charge). When I reset the garage's 240v circuit breaker, the EVSE comes back on and boots up just fine, but then shuts down again a short time later. Any suggestions?

 

It's hard to know without seeing it, but it sound like a 5V power supply issue. When you power-cycle, the power supply is temporarily good enough to boot up, then it goes sour. Just guessing. It could be something else, but many people have had power supply issues with the Coulomb CT500.

My CT-500 has its third failure:

• First failure, in 2011, was "relay stuck closed" error message on the LED display.
  • I got a refurb replacement unit via warranty.
• Second failure, in 2017, was that the plastic quick-connects that attach the J1772 cord to the unit had melted and lost connectivity.
  • I fixed by replacing some of the internal connectors and cabling.
• The third failure, today in 2025, is the entire unit seems dead. The LED is dark, etc.
  • This seems like the 5V power supply is bad, but I haven't verified yet.

It makes me wonder, presuming I manage to fix it, how it will fail again in 2033. Seems like each fix is good for only 8 years

 

Well, it took me a few months to get around to it, but I have resurrected my Coulomb/ChargePoint CT500. Again.

It was indeed the power supply. Mine was completely dead, instead of having a wandering voltage where the CT500 shows some life but doesn't behave correctly.

The AEVA post discusses power supply details. It's made by TDK-Lambda and is supposed to be medical-grade super reliable, but they seem to be the opposite of reliable. They're also expensive. I decided I didn't want to spend that much for an exact replacement.

The blue rectangle in this image is the bad TDK-Lambda power supply:

My soldering skills are pretty weak, so I decided I didn't want unsolder it from the PCB. (Side benefit, I didn't have to unscrew the PCB from the metal plate.) I decided instead to try to cut it out with a dremel tool. This was time consuming and made a huge mess. It didn't come out cleanly, but I had to cut out and remove small bits at a time. But I eventually succeeded.

I was left with only the bottom plastic bit of the power supply, with four metal posts protruding. I was hoping (and later confirmed) that the four metal posts were two A/C inputs and two D/C outputs. In this picture you can only see three of the posts, because I took a chunk of the crumbly insulation stuff and embedded the top-right post with it. (I was originally thinking I'd power the replacement power supply external to the PCB, but then changed my mind.)

Here I've attached four white springy connector things to the four posts. I have never used these before, and I'm not super confident in them. (I think it would be better to use screw-tightened connectors, but I didn't have any. Or to solder the wires to the posts and cover with heat-shrink tubing. I did try using wire nuts, but the posts didn't extend far enough for them to bite.) Not shown in the picture are four pieces of insulator tubing, which I used to surround the four white springy connectors.

Here the purple and white wires are the two A/C inputs to the new power supply. (White is marked Neutral and purple is marked Line, but since this will be plugged into a standard USA 220 circuit, both will be hot.) I didn't have the new power supply yet so, to avoid shocking myself, I temporarily capped the end of these two wires with wire nuts.

The yellow wire is D/C +5V. The blue wire is D/C ground. I figured I had a 5V D/C power supply in my house somewhere I could use to test, but had trouble finding one. I eventually found the power brick that came with an old Belken USB 1.x hub. It outputs 5VDC at 2.3A but, unlike most modern power supplies which can handle 120V and 220V just fine, this one's A/C input isn't supposed to go above 120V.

So I plugged the Belkin power brick into a regular 120V circuit, jury-rigged a connection to the yellow/blue wires, and it came back to life!

I should mention that I gouged out a small section of grey plastic cover for the four wires to go through, so they wouldn't be pinched too much.

This was good enough to charge my vehicle. I plugged the CT500's cord into 220V, and also used an extension cord to plug the Belken power brick into 120V.

So far so good. Now to give it a real power supply.

I decided I wanted to buy a Mean Well RS-25-5 power supply, which accepts 88–264 VAC and outputs 5VDC at 5A. You can find one for less than US$20.

But I accidentally bought a Mean Well RS-15-5 instead, which is similar but outputs 5VDC at 3A, not 5A. That should be good enough. The original TDK-Lambda KMS15-5 also outputs 5VDC at 3A. And I have disconnected the 2G cellular modem from power anyway, so it probably doesn't even need the full 3 amps. The Belkin power brick was 2.3 amps.

Here is the Mean Well RS-15-5, pictured next to a block of styrofoam that I had cut to approximate the size of the RS-25-5. (The RS-15-5 is slightly smaller than the RS-25-5, 63×51×28 mm vs. 78×51×28 mm. Both are 5mm wider than the original TDK-Lambda unit, which was 64×46×24 mm.)

Here it is installed in the CT500.

And here it is back on my garage wall, charging my vehicle. (No 120V power brick and extension cord this time.)

It's only been five hours, but so far it works fine. My car has completed charging.

Hopefully I don't regret using those white springy connector things. My CT500 has already died three times. I shouldn't be surprised if it dies a fourth time.

With the outer cover back on, it looks the same as it always has: