blown a DCDC converter

Had a 15W dcdc converter from Lyen, worked fine for a few minutes then trying it with a multimeter it all of a sudden started outputting the source voltage on the output terminals, I've heard about this happening to this type of DCDC converter and blowing lights / grear that's connected, didn't expect it to fail so soon.

I really urgently need a solution for going from 50V to 12V can anyone recommend anything? everything available in the UK is either fixed 12/24V or 32V maximum. Is it fairly simple to roll your own converter?

Look here:
Cheap DC-DC converters for over 60v input.
http://endless-sphere.com/forums/viewtopic.php?f=16&t=2264

38,841 DC/DC Converters for sale here:
http://www.mouser.com/Search/Refine.aspx?N=254455

Same thing happend to me with same lyen DC/DC converter
It worked fine for a few months then I plugged it in while my pack 16S life was fresh off the charger
and pow, blew my 100 dollar headlights.

I think it was just at or above the input voltage limit with the batterys freshly charged up to 58 volts or so.
I should have waited a few minutes or discharged the pack for a second before hooking it up.

It would have been good to have used a dc/dc converter that is isolated so if anything ever goes wrong,
the voltage from the input doesnt appear at the output.

difficult to do. I've heard several cases of these lyen dc-dc's failing and killing the gear. Trying the mehtod of using a 2A switched power supply from a powertool charger to see if that works, feeding the 240V AC input with 50V DC and see if it will still happily pump out 12V DC. Results to follow.

How could you isolate the dcdc to protect against a full voltage throughput, a fuse won't work will it? on my trike I have a proper PCB that has the DCDC on it to go to the various 12V devices then a further 5V dcdc.

any dc-dc with a primary-secondary transformer would be isolated.

I carved open the Lynn dc-dc converter I dont remember seeing any transormer in it.
I think the dc-dc chip was a national semiconductor (now TI) chip and if I remember it was rated at its high limit for input voltage in.
who knows maybe it was counterfeit or something.

I am using a "laptop PC" power supply on 16s (59.9v nominal) rated for 12v 5A output. It is isolated.

I've run the batt down to cutoff (~52v) and the power supply still ran fine.

I had to try 4 different ones before I found one that worked. Good thing I had them laying around.

It has held up to a good deal of abuse, I don't think I will ever go back to the "DC/DC converters".

I also fused the input and output this time, but haven't blown one yet anyway. Better safe than sorry.

Later,
Jay