Cheap LM2596HV dc-dc converters that BLOW UP

[fechter]

I needed a low power dc-dc converter that can run off my 14s pack and output 12vdc. Pack is 59v hot of the charger. I found tons of ads for these dc-dc converter boards on eBay and bought 3 of them. The ads specify input range of 4.5v to 60v. Perfect, right?



I tested the board after it arrived. It blew up at around 52v. Close, but no cigar. I chalked it up to quality control, so tried another one. Same thing, only this one blew at about 54v. Bummer. But they were dirt cheap to start with.

If you check the datasheet for the LM2596HV, it indicates this part is out of production and no longer supported. WTF? I guess the ones they are selling are fakes. After some research, I found they make a new part, LM2592HVS, which is supported and "pin for pin compatible" with the LM2596, and rated for 60V. I found them at Mouser and got a couple. I replaced the chips off the fried ones, and YES, it works nice.

 

[Gregory]

Ha , nice fix , bet it tripled the cost of the board!

I'm pretty sure I received one with 50v cap across the input. I threw it in the scrap bin. But they are so irresistibly cheap.

 

[fechter]

Ha , nice fix , bet it tripled the cost of the board!

More than triple. The new part was $6.35. But to me it's worth it since now it works well and I haven't found anything that size that handles 60v.

 

[heathyoung]

Yeah I found a few of the exploding knockoffs too - wasn't real impressed...

 

[LewTwo]

I also have a couple of these. My thought was to use a zener diode ahead of them to reduce the voltage down to 48 volts first.

 

[fechter]

I've done that before. That will work if the load is small enough. The zener diode will get pretty hot.

 

[LewTwo]

I've done that before. That will work if the load is small enough. The zener diode will get pretty hot.

Waste heat should be proportional to the voltage drop .. worst case 12 volts from 60 .. better case 4 volts from 52 ... best case 0 from 48. If it was going to be much of a load I would not use one of these.

 

[multifrag]

I have multiple LM2596HVS converters and let me tell you that some of them are just re-branded LM2596HV... For now, I only had 2 out of 6 to be fake. Both fakes where from one seller.