power supplies in series question

Just asking before I blow up 2 of my power supplies that I just made/salvaged/fixed/modified. I need 19 volts at 2.95 amps (practically 3) for a laptop that I found (yay dumpster diving, don't worry I'm not a guy who steals identity, it was actually my dad's lab and they're throwing away a bunch of stuff, it's a goldmine!) and it was marked dead. I pull out the battery and it has 0 charge. It had no charging adapter, so can I just make one? I have to power supplies, one from a computer that I modified and an adjustable one the goes up to about 15 volts at 6 amps (and they were throwing it away! it only need a new fuse). After all of that background info, here's my question: can i put the 5 volts from the comp supply in series with the 14 volts from my adjustable supply to get 19 volts at enough amps to power on this laptop? I don't want to buy a 60 dollar charger just to find out the comps broken cause of something else.

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HVahead6 years ago
HVahead6 years ago
sorry for posting on the dead thread,but...
youd need to float the psu, that is, disconnect it to ground...hold on
guyfrom7up (author) 9 years ago
It worked unfortunatley my laptop didn't
keep the laptop. im working on an instructabel on what to do with failed computer parts.
guyfrom7up (author)  tech-king9 years ago
ok, I will. I cracked open the battery to find 8x 18650 lithiums. I think it's 4 in series in parallel with the other 4 in series. The combined voltage of everything is 6 volts, and it should be 14.4. I'm going to take the batteries out, hook up my power supply (do you think 12 volts will work, it'd be much more convienient) to where the batteries should be and see what happens. If all goes well I'll go buy some 18650's. If this is a bad idea tell me soon, lol.
The only real "bad idea" here is anything that tries to charge the batteries without going through the laptop's charge control circuitry. If you know what you're doing, fine, but just make sure you know what you're doing before trying anything like that.
guyfrom7up (author) 9 years ago
alright, I'll test it, what's the worst that could happen? I think it should work because of the ground. For example: Lets say you have a 7805. +12 volts in, +5 volts out. If you change the ground (relative to another ground, as in the 1st power supply in series) to something like +2 volts, then the output should be 7 volts, right? I'll try it once I buy some connectors for my comp supply. I feel like I've made sooo many power supplies, I have: a mini one (about the size of the old fat ipods) that supplies 5 volts at 2 amps, and 12 volts at 2 amps. I just finished it. a variable one, I couldn't fit capacitors in the case, so they're external. It has 2 outs, 8 volts at 6 amps, and 3-15 volts at 6 amps. It even has an ampmeter built in! I didn't make this, I just fixed it and changed the ac output to dc. a computer one, I put on my load resistor today and everything works, all I need now is connectors and I'm done.
 So did it work? I'm trying to do the same thing with 2 ATX power supplies salvaged from old computers to get different voltages
tech-king9 years ago
to be truly honest, this is something i want to know too. seeing as its dc, its possible it works. you could possibly dry run it and use a multimeter to find out if it gives 19 volts. however, somehow, i dont think it will work.
If they are regulate supplies, the regulator will clip the voltage to the prescribed voltage.
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