Building Out an M18 60v 20A Power Supply - Fun with Diodes and More (Part 1)

[@SuperBrainAK]

So uh, you picked the wrong diodes, as far as the batteries are concerned there are no diodes, it is shorted through the aluminum. I wish you well in your future projects. Just keep experimenting!

[@TalkingHandsTools]

Thanks, I'm game to make modifications for the better. What should I use to do what I'm looking for? Currently, the batteries are isolated, and with the plastic fasteners, the aluminum heat sinks are insulated in the plastic box. I never claimed semiconductors were my strong suit. If there's something that's a better fit, I'd like to use it. Part of why I like to make videos is to show it's okay to learn as you go and make changes. If you have a good idea, I'll put it on the project and include it in a future video. I have another upgrade planned already. Thanks for the comment.

[@SuperBrainAK]

@@TalkingHandsTools So my recommendation after watching the video is that you want to swap the diodes around. You had the right idea of "ground" being battery negative but that isn't really feasible in this application and trying to keep that idea led you astray. I'll explain why in the next paragraph but what you need to do is remove the diodes on the negative heatsink, put them back in your diode drawer. Then take the diodes you used from the positive side and mount them to the negative side heatsink. Connect the negative battery leads to the small tips of the diodes, and the negative of the boost converter to the negative heatsink (the large threaded metal part of the diode). In your final configuration shown at the end of this video is not ideal at all, you don't need 4 diodes just 2. On the negative side, the negatives of the batteries are shorted together through the heatsink, then you connected the other ends of the diodes together. Which is why you could see the current flow between the batteries, the only thing the 2 diodes (acting as a single diode in parallel) would have prevented is the boost converter from accidentally charging the batteries (which it's already impossible due to diodes already in the module). You were on the right track with adding the positive diodes by isolating the heatsinks. However you should just take a step back and combine the 2 ideas. Don't use the negative diodes because they did nothing and isolate the 2 batteries by using the non heatsink side of the diode. So do what I said earlier, use the other polarity of the diodes and mount the battery terminals directly to the tips of the diodes. I hope this helps! Diodes can be a tricky thing, especially when they mount to a heatsink and that then becomes part of the circuit. This is the reason why most semiconductors have isolating pads on them because the back tab is connected to the center pin which is the Gate/Collector!

[@TalkingHandsTools]

I can definitely see that would work. I was thinking I should only need two diodes, but I ended up spun around on things and had the batteries in parallel. Thank you. I'll try and incorporate this change in a future video. There's already at least one more video part that'll go out first, and then we can get into the modifications. To anyone reading this is the fun part about building things, sometimes you get it wrong but it's okay take a step back and coarse correct a little and everything will work out and you'll learn something along the way. Thanks again!

[@SuperBrainAK]

@@TalkingHandsTools You're welcome! Happy to help! Yes, when you are building no matter how much experience you will eventually mess up. Just learn what went wrong and keep on building. You'll only get better and better!