Meanwell PS creates a load?
Recently realized that my solar systems daily output had increased by ~50Wh per day when in storage with no shorepower. It was hard to believe that the parasitic loads or the battery self-discharge...
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Finally read the manual of my clamp-on ammeter. For repeatable readings I need to zero it each time. It has a 1ma resolution. Anyway, 70-75ma seems about right for my Meanwell's back current when unplugged.
So, just for fun, I ordered a few, very cheap Schottkey Rectifier type MBR60100PT (60A, 100V, TO-247 case) from China. The MBR60100PT has two diodes with a single joined cathode lead but separate anode leads. I sandwiched the TO-247 case between two pieces of copper angle with the cathode folded over and soldered to one angle and the anodes to the other. So 2 diodes in parallel.
And sure enough, the Meanwell's back current dropped to 0-5ma when unplugged.
When I then tested the Meanwell under max load charging the batteries, it put out 24A forward current at 25.2V (605W!). Using an infrared temperature gun, the copper mounts got up to 80C right at the TO-247 case leads. You have to wonder how the small leads of the TO-247 case can handle up to 60A! I didn't attempt to measure the V drop across the diodes as that can be compensated for by adjusting the Meanwell's output.
So it worked, but just not sure how long this will last with these lead temperatures. We'll see. It will only rarely be used with this high a load, and the Meanwell fan does draw air across the device.
A more robust (and expensive) diode like Mex suggested earlier would certainly be a better solution.
Some notes:
The amount of current Schottky diodes pass thru increases with their temperature. So when in parallel you can get thermal runaway with only one diode handling all the current. I mounted two TO-247s (4 diodes, 2 per case) together in the copper sandwich. But only one of the devices heated up and, presumably, was passing all the current. Dunno if both diodes in the TO-247 were sharing the current equally, as I couldn't measure the temperature of the individual anodes.
The metal backing on the TO-247 devices I have is connected to the cathode. So I had to be sure the cathode was soldered to the copper angle touching the metal back. I had that reversed initially. :(
So, just for fun, I ordered a few, very cheap Schottkey Rectifier type MBR60100PT (60A, 100V, TO-247 case) from China. The MBR60100PT has two diodes with a single joined cathode lead but separate anode leads. I sandwiched the TO-247 case between two pieces of copper angle with the cathode folded over and soldered to one angle and the anodes to the other. So 2 diodes in parallel.
And sure enough, the Meanwell's back current dropped to 0-5ma when unplugged.
When I then tested the Meanwell under max load charging the batteries, it put out 24A forward current at 25.2V (605W!). Using an infrared temperature gun, the copper mounts got up to 80C right at the TO-247 case leads. You have to wonder how the small leads of the TO-247 case can handle up to 60A! I didn't attempt to measure the V drop across the diodes as that can be compensated for by adjusting the Meanwell's output.
So it worked, but just not sure how long this will last with these lead temperatures. We'll see. It will only rarely be used with this high a load, and the Meanwell fan does draw air across the device.
A more robust (and expensive) diode like Mex suggested earlier would certainly be a better solution.
Some notes:
The amount of current Schottky diodes pass thru increases with their temperature. So when in parallel you can get thermal runaway with only one diode handling all the current. I mounted two TO-247s (4 diodes, 2 per case) together in the copper sandwich. But only one of the devices heated up and, presumably, was passing all the current. Dunno if both diodes in the TO-247 were sharing the current equally, as I couldn't measure the temperature of the individual anodes.
The metal backing on the TO-247 devices I have is connected to the cathode. So I had to be sure the cathode was soldered to the copper angle touching the metal back. I had that reversed initially. :(
