DC/DC converter troubleshooting

I'm taking a lot longer than expected to wire my DC DC converter and, worse of all, I'm not having any success.

I'm using a TDC-IY-108-12 from a Chinese company named TC Charger (the website www.tccharger.com printed in the manual doesn't exist). I think there are similar converters branded as Elcon. It's a 1kW unit with a nominal DC input of 108V (range can vary from 72V to 162V).

DC/DC converter wired up but not working
DC/DC converter wired up but not working. I know, the junction box needs to be sorted out! This was the result of many trial and errors :)

The manual is, like most of these Chinese units, pretty poor and ambiguous. But since the connections are not so many, I really thought it would be much more straightforward than what I've been experiencing.

There is a 12V output which I connected to the 12V battery through a large 100A megaval fuse. The ground pole (which in turn is connect to the converter chassis) is connected to a good ground in the vehicle chassis.

DC/DC 12V fuse
100A 12V fuse between the converter output and the vehicle 12V source (where the alternator used to be)

On the HV side of things, used the supplied 4 pins connector to connect to the HV battery negative and, via a minitactor from Gigavac, to the HV battery positive. I say 4 pins but that's on the converter side. Two pins are the so called HV interlock and I think they are short-circuited on the connector and are not available in the back of it. I believe it's for the converter to know if that connector is correctly inserted and disable itself if not.

Converter connections
Converter connections, from left to right: 12V ground/chassis (black), 12V output (red), 4 pins control (black) and HV connector (orange). If I'm reading the manual right, 1 is the HV positive and 2 is the HV negative. I tried both :)

By the way, for the HV supply, I'm not using the final Nissan Leaf pack with a 32s configuration. I'm keeping the risk lower and using 5 20V battery packs from Parkside/Lidl. The same I used before for the traction test. It outputs around 96V, which should be well between the valid range of this converter (72V to 162V). The under voltage protection is supposed to trigger only at around 70V.

There's an additional 4 pins connector for control. This is where it gets trickier. Again, there are 2 pins named HV interlock, which I assume (unfortunately we need to assume a lot of things due to the poor documentation) work the same way as the HV connector, ie, we need to shunt. I did.
There are two other pins, named Enable and Failure Signal. Firstly, I could understand the pinout -- more specifically, if the drawing is seen from the front or back of the connector. So, I might be switching these two pins but I tried fiddling with both.

Accordingly to the documentation, the Enable input needs a 6V to 30V signal and draws less than 1mA. I don't know if it's an high voltage to enable or otherwise but I tried leaving it open, connecting to 12V high and 12V ground, either at startup and after but nothing.
Since there is no CAN bus (the manual talks about it but I guess it applies only to other variants) or LEDs, all the feedback I can have is through the Failure Signal. Again, there's no clear documentation and the electrical schematic doesn't help (they keep changing the labels/wire names!). In my case, I always read a 0V signal (referenced to 12V ground). I don't know if that's an indication of fault or not.

In practice, the converter output is not the 14V or thereabouts but just the 12.4V the battery is already with when not loaded. So I guess nothing is working. I could use a multimeter to measure the current going from the converter to the car but I'm afraid the 10A rating of the multimeter is not enough. But I will try it nonetheless.

I already tried reversing the HV inputs but still no result. According to the manual, that's safe to do because the reverse voltage protecting on the input will simply disable the converter. No matter what I do, the converter simply seems to not do anything.

It's also worth mentioning that the HV input fuse blew up on the first try in the car (after some tries in the workbench), even though I was using a 600VDC 30A fuse from Littelfuse (fast-acting) while the manual says the max amperage is below 11A (in rush of 4A). I was brave (stupid?) enough to try without it but the results are the same.

DC/DC input fuse
DC/DC input fuse blew on first try. It was a Littelfuse 600VDC 30A fast-acting. All runs after that were unfused (yeah!). I guess I need to order a 40A or 50A fuse.

I've checked some forums with discussions about similar converters. Some mention that the Enable signal should be connected to the HV battery positive. I haven't tried that because the manual specifies an input range of 6V to 30V. I'm not that desperate, yet...

Do you have any more ideas?


Rene Hamer (not verified)

First, thank you so much for these postings. I enjoyed reading and learned a lot. We just decided to convert our samurai to EV. You provided a world of information. Thank you.
DC/DC convertor trouble. I have electronics background. So, more comfortable reading manuals and getting electronics to work.
The user manual is pretty good. The unit is well protected against wiring mistakes.
Do not ever run power connections without proper fuses. If a fuse blows, something is wrong. Never bypass the fuse, especially in these high-power applications it can be lethally dangerous. But I think you know that.
The control signals, inputs and outputs are all on the low side of the unit. Do not connect any of them to the high side. (HV side.)
I think the unit is broken.
But you can do some more test to see if anything is alive.
I agree, the naming of signals is confusing.
Connect the HV line with fuse please.
With a voltmeter measure the EN_EXIT pin to chassis ground. It should read 3.5 V.
You can connect it to 12 V, or being Chinese, connect it to chassis ground. The way I read their document; it can be left floating. Enabling with 12V, when you have a flat 12V battery does not make any sense. Enabling to ground always works.
The Fault output is confusing, but according to the document, it’s a sourcing output. Again, measure with the voltmeter, I think, if there is no faut the signal is 14V. You can connect an LED to this output.

I hope this helps, good luck getting it going.

Thu, 2021-07-29 Permalink

In reply to by Rene Hamer (not verified)

Hi Rene,

thank you so much for your help. I've been busy with other stuff (some not related to this project) but now that I finished the BMS wiring I'm ready to test that. Next, I will return my attention to the DC DC converter. I feel I was procrastinating this troubleshooting a bit, maybe due to the lack of results so far :P

Thanks again for the helpful words.


Fri, 2021-10-08 Permalink
Alexander Bade (not verified)

I'm at the same stage as you described in this post. I really tried everything to get this thing running. When I read the comment from Rene I thought it was broken. So I testet another unit to proove this. But same thing, no voltage rise after key switch on.
So do you have a solution to this now?
My evshop told me the brown wire is the enable pin - so I connected it to 12V key. I connected HV positive and negative, the Chassis to Ground and the red wire to 12V with a fuse in between. So I don't really know what else I could test to get this running.
Would be happy for any suggestions.

Kind regards

Thu, 2021-11-25 Permalink

In reply to by Alexander Bade (not verified)

Hi Alex,

Thanks for sharing your experience. I've connected the converter just like you mention (and tested some other ones ways, namely the Enabled input) but no luck!

I confess that at a point I thought it was simply broken and I preferred to focus on other stuff that needed my attention, such as the traction battery pack. So, I have no more news about the converter.

But now that you mention the same problem.... with two different units, that's even weirder!
Could it be that the quality control is that bad? I've seen some people using this same converter, namely the guys at Zero EV on the UK, so I had some hope it would work ok.

Please let us know if/how you nailed this one out at some point!

Best of luck,


Thu, 2021-11-25 Permalink

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