I bought this voltage regulator and when i connected the IN terminals to a Li-Po Battery (image attached) a resistor or whatever circuit exploded. Can someone explain to me why this happened? I am new to electronics and DIY. Thank you!
I think that component is a reverse polarity diode. But even with the correct polarity, too much current = explode.
I guess either the module is faulty, or there is a short on the output, or too much current draw on the output.
how can i measure how much current is drawn before connecting the new module and destroying it again?
Might just be the picture, but is that battery pack swollen? If so, it would be incredibly dangerous to continue using it, LiPo batteries can catch fire when damaged.
Did you have a load connected before you powered up the regulator?
Good question, first thing to do would be to find a schematic for it. Then maybe measure resistances at various points.
For this sort of thing, a bench PSU which can be set to limit current is very useful. You could maybe test with a smaller battery. To measure current, put your meter into a suitable mode and connect in series with one of the power terminals.
After replacing the Diode I would use a lab type power supply where I can adjust the current and voltage. I would start about 250 mA and the voltage at zero and connect it. then slowly raise the voltage to maximum. if you go into current limit it is damaged, probably shorted. You can get a replacement SEPIC converter for about a buck, currently free shipping: https://www.aliexpress.us/item/3256807859620017.html? The price changes in different countries so that price may be off. It is probably best to trash it and get a new one. Double check connections before powering up. SEPIC converters are automatic Buck/Boost, great for battery systems but they generally use a little more current.
What do you mean "keeps exploding"?
How many have you blown-up and did you do the exact same thing when you blew-up each one, using the same battery?
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Why would it be connected that way?
I think it's a pointless attempt at reverse polarity protection. I've seen this in a few designs, I guess it gets copied from other circuits.
I assume the OP has double checked their polarity...
It is reverse polarity protection (for the regulator circuit). BUT to work properly it needs a fuse in series so the fuse blows when the diode conducts excess current. Otherwise, you can damage the power supply, battery, or the diode itself.
Of course, the same thing can happen (blown diode, fuse, power supply, etc.) with the correct polarity if the diode is installed backwards.
...It's reverse voltage protection, not current protection. When the fuse blows that stops the excess current flow, hopefully before anything else blows up.
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Show me an example of another design (except the one on Instructable)
My thoughts where going that way, and as you said it needs a fuse otherwise something of more value will go up in smoke.
That's not the point, I'm asking because what I can see, this circuit would take down either the diode, then the regulator, or the power source. See @DVDdoug 's answer. If there's a fuse the use of a diode like you proposed will make sense.
If I would use a diode (which I won't), I'd place it in series with the circuit. (Not optimal, because of the voltage drop over the diode.)
A series diode is better if you have enough "extra voltage". Just remember that battery voltage drops as it discharges and then you don't have as much extra voltage.
It's also possible (although very unlikely) that the battery wire colors are reversed, if you haven't checked with a multimeter or something.
The diode does protect the other components on the regular board. The damage would be worse without it. The manufacturer is trying to protect their board. They could have included a fuse, but sometimes I've seen a soldered-on mini-fuse so it's still not so easy to repair.
It's more probable that PCB labeling is reversed or OP's eyes are reversed...
Best reverse polarity protection is for the purpose made IC's, or a MOSFET circuit. Afrotechmods vid on YT about a FET solution is nice.
it is slightly swollen.
Those are bad boys if not handled carefully. 50C discharge rate translates to more than 250A...