24V-to-12V DC-to-DC Converter Blowing Fuses

I am setting up a 24V system and bought a converter on Amazon. I tested the 24V-to-12V converter with a 24V power supply and it works fine. When I connect it to the batteries for my solar system, then it blows a fuse. I am using a 30A fuse and don't have a load on the converter. I realize that there is current needed to charge the input capacitors for the converter, but blowing a 30A fuse seems excessive. Has anyone else run into this? Is there an easy fix?

No, but If you dont have a sustained arc or sparking, it shouldnt break the fuse. If there is a switch it could help.

Usually after the inrush is satisfied, it wont spark heavy again right away. I usually just tap the wire to the terminal screw then land on the terminal.

Double check polarity. Its one sure way to instantly blow a fuse if the device hs reverse polarity protection.

It does seem excessive.
You could prime the caps with the power supply and then quickly switch to the battery.
If the fuse still pops then dig deeper.

I tried using a 200A breaker as a switch. The breaker was in series with a 30A fuse so I had a reasonable amount of current protection. I used approx 16 gauge wires with alligator clips to connect the circuit breaker to my fuse box with 30A fuse. When I closed the breaker, the 30A fuse did not blow, but the 16 gauge wires started to get very hot (hot enough that the insulation started to get soft). I previously tried charging the caps with a 24V/1.2A supply and then switching over. That also did not work.

Baduk said:

I tried using a 200A breaker as a switch. The breaker was in series with a 30A fuse so I had a reasonable amount of current protection. I used approx 16 gauge wires with alligator clips to connect the circuit breaker to my fuse box with 30A fuse. When I closed the breaker, the 30A fuse did not blow, but the 16 gauge wires started to get very hot (hot enough that the insulation started to get soft). I previously tried charging the caps with a 24V/1.2A supply and then switching over. That also did not work.

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Very hot wires does not sound good.
Can you post a link to the converter?
Does it still work with the power supply?

The link is here. It is the Cllena converter.

Baduk said:

The link is here. It is the Cllena converter.

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Gotta ask. You didn't hook it up backwards, confirm?

Some of those dc-dc units are marked backwards. So just in case yours is fubar the red wire goes to 24v.

I use this gizmo to prevent the arcy sparky when connecting things. It precharges capacitors and/or otherwise brings things to similar potential when connecting stuff. It's two 25ohm 100 watt resisters in series with two (paralleled together) inrush current limiting thermistors that I just screwed down to a piece of wood. It works great. Just place this in series with the item you are connecting then disconnect after making direct contact. For example when connecting a battery cable I'll clip one end to the battery terminal and one end to the cable terminal. When I touch the cable terminal directly to the battery terminal, no spark. Then unclip the gizmo. I use this every time I connect things to a live DC circuit. I never get a spark or blown fuses. The gismo has no polarity - ignore the color of the alligator clips - so either way you connect it is fine.




The parts:

Nope, it wasn't connected backwards. I think I got a bad one and am going to exchange it.

Thanks for the circuit! I'll check my junk box for parts.

Baduk said:

Nope, it wasn't connected backwards. I think I got a bad one and am going to exchange it.

Thanks for the circuit! I'll check my junk box for parts.

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If you have those inrush thermistors in your junk box then you're probably an HVAC tech.

@onemorebattery

Thanks for the simple, effective tool.