Last May (2020), the same thing happened to me. I posted the following on the community pages recommending an immediate recall of the BECs - only to have my post immediately removed! It seems I am not the only one to have found this problem, but Zach and Paul’s response last year was to remove my post and not let the community know. I wonder if anyone has had their system explode in flight? Zach, Paul – please do not remove this post.
I am still waiting for my replacement parts.
Here is my post from last May that was removed:
Exploding BEC Regulator!
Hi Paul (and Zak) Pdwhite zjwhitehead
I haven’t been able to put as much time into finishing off my batch 5 paramotor as I would have liked, but hopefully you would have found some of my posts of investigations into battery testing and construction interesting. But I have now found something rather concerning.
Two days ago, I was finishing things off and preparing for my first thrust test using my 18650 battery pack (14S16P). Everything was looking good.
Sometimes I noticed that not all the motors/ESC would initialise properly on start up, and only a full power cycle would clear this. I was investigating why this should be, when the DC-DC converter BEC that you supplied exploded! A piece of burning shrapnel only just missed me!
The DC-DC converter BEC that came with my batch5 is one of the cheap units from china. It uses the NatSemi LM2576HVS buck converter controller. The HVS version is rated to 60V (63V abs max).
This regulator should be bullet proof. There is not much you can do to make it explode like this. (There is nothing wrong with my wiring!)
I am strongly suspecting that this regulator module may have been built using a ‘fake’ regulator device! The standard LM2576 regulator is half the price of the HVS version. There are companies in the far east that re-brand (re-print) the LM2576 as LM2576HVS and can then sell them at twice the price.
The lower voltage devices are rated at up to 45V. So, along comes my freshly charged battery pack at 58V, and it blows up!
In the thread “Carbon Props Experiment” grejen711 talks about the ESCs needing a re-boot. This was the sort of issue that I was investigating when the BEC exploded. From the experiences of others on YouTube who have encountered fake regulators, the LM2576 can go into all sorts of weird modes before failing.
So, I must recommend a recall of these BEC regulators. Or at the very least, anyone with one of these BEC regulators should run it at close to 60V for an hour or so (with nothing connected to the output) and see if it goes bang.
I have replaced the LM2576 with a genuine LM2576HVS and the BEC now works and the main controller lights up. But it seems to have taken out my throttle controller!
Paul/Zak, could you please send me copies of the schematics of the main controller and the throttle controller PCBs so I can work out what might have happened to this so I can fix it??
And others with this BEC, please treat it with deapest suspicion!