EEVblog #1036 - PSU Fire PCB Repair

[Nusa]

Other than that, it powers on and seems to function.  It's a bit short on max volts.  My bench supply is providing it with 30V, it allows me to set 29.0V but registers 27.15V.  Although it has no load.  The DMM confers to within a few tens of millivolts with what it reads.

That seems to match the specifications for all the DPS models, which state the input voltage must be 10% higher than the output voltage.

[paulca]

Well, device works fine.  I've loaded it up to 12A, 12.60V with a LiPo and it works as advertised.

Nowhere near as precise as my Tenma bench supply though.  When charging the LiPo with it, it switched from CC to CV at 12.49V instead of 12.60V.   Thankfully it was that way and not the other!  Don't think I will trust it for finishing the LiPo charge, but it can charge a 5000mAh at 2C up till it gets to CV mode then I'll use something more trust worthy.

Oh and... the mains switch on the back failed already.  My suspicion is they don't use high temp plastic to hold things together and the spring has shifted during soldering.  You can push the switch, tap it, thump it, but it will not "click" and go off.  So it's stuck on now and I have to pull the plug out of the wall to kill it.

I'm adding a master switch to my TODO list to beable to kill both my power supplies with an easy to reach switch.  Currently if magic smoke starts to be released I have to climb under the desk and pull the plug, then come back up and switch the Tenma off too.

[HKJ]

Nowhere near as precise as my Tenma bench supply though.  When charging the LiPo with it, it switched from CC to CV at 12.49V instead of 12.60V.

Could that be user error, i.e. you are using thin wires and measuring at the battery, not on the ps board output terminals?

[paulca]

Nowhere near as precise as my Tenma bench supply though.  When charging the LiPo with it, it switched from CC to CV at 12.49V instead of 12.60V.

Could that be user error, i.e. you are using thin wires and measuring at the battery, not on the ps board output terminals?

Nope.  Using a dedicated banana to XT60 LiPo lead, it's about 14 AWG, 6 inches long. 

I was going by what the DPS reading said.  It was saying 12.60V set, 12.49V output, CV.  This was literally on the corner between CC and CV, so it might be more to do with a linear region between the two where the display says CV when it's really in that linear region between CC and CV.  I stopped the experiment there, but I would expect as the battery charged and the amps fell more it would come up to 12.60V (ish). 

EDIT:  Input voltage from the DC supply still reported 48.7V