[IdeaBeing]

Before I attempt this, I thought I'd throw it out there.

If I have 2 identical 12V wall warts of 2A capacity and connect the leads in parallel, will I get a safe 4A @ 12V at the barrel connector?

Would I need to power them up at exactly the same time (power bar?) to prevent backflow from one into the other?

I'd like to power my LiPo charger with this rig, as I find it difficult to find affordable 12V adapters except for these 2A units from Active Surplus on Queen St. West in Toronto

If this is a fire/electrocution waiting to happen, does anyone have any leads on affordable high-capacity (5A+) 120V-12V adapters?

[Terry Gauvin]

It does sound like it should work doesn't it? But it doesn't, you can't gang power supplies that way.

[Real Gambler]

Well, I would say that it depends on the wall warts design.

If they are relatively light, do not do it! They are likely switching power supply, and as such, can provide very regulated output. Having two output slightly off, one will most likely damage the other.

Now, on the other side, if they are your typical old wall wart weighting a ton, then it may work. You have to check the output first. If it does seem very regulated, then I would not do it. Again, because the output will likely be different on both, one could damage the other.

You last possibility is simply the good old wall wart with almost no regulation built it. Weight a ton, but as you put a load on it, the output voltage will vary from 18 volts (no load) to sometime less than 12 volts under load. Basically, those would work because they are only a transformer, a diodes bridge, and a few big capacitors. Sadly, they are usually quite noisy (output), so I'm not sure a cheap lipo charger would like that.

So the question is more: Do you feel lucky? I would suggest NO.

Personally, there's more and more laptops being recycled. Many of those laptops had 4amps 12volt up to 19 volts power supply (Check your Lipo charger rating, since many of them don't like more than 18 volts). So just ask around in your family... You may get lucky and get one of those for free from somebody who's recycling a laptop. Those are switching power supply btw, so don't worry if you cannot read the output with no charge. Some of those old ones would only work with a load connected to them.

Do not use the power supply from a good laptop. Sometime they were designed for a particular load in mind. You should not damage it, but hey, I don't want you to sue me if you do. It's a good way to give a second life to an old laptop power supply being recycled!

[kip51035]

Several of the A/C I worked on had two generators and they had a special rig that kept them in PARALLEL and if they were not one would try and turn the other into a motor causing great clouds of smoke, maybe if you ran them through a couple of diodes.

Kip

[Spitball]

If you put them in parallel, with or without diodes, there is absolutely no guarantee that they would share the load, even remotely equally. Save yourself grief and buy a bigger power supply - good investment in the end. Someone is getting me two 12volt 5Amp switching supplies from - guess where - at $9:99 each! These are like lap-top supplies which, BTW, are invariably 18 or 19volts as far s I've seen.
Edit: Before everybody jumps for the keyboard, yes, you can modify computer power supplies and I've done so myself but they're bulky and you're using about half their capacity which is sometimes many times more than you need - it's a damn chore and not everybody has the knowledge to do so.

[IdeaBeing]

Thanks for the warnings and advice regarding the adapters. I ended up going with the ATX PC power supply solution. A 350 Watt supply from an obsolete PC I had lying around provides 8 amps of clean 12v power, provided you solder in resistors across the 5v rail to simulate the load of the MotherBoard.

I used 2 x 1ohm resistors rated at 20 Watts each in series and zip tied them to the case of the power supply with white grease in between for heat conductivity. In addition, I bolted the CPU fans to the case above the resistors to exhaust any excess heat and wired them into the 12v rail (they are 1.5 Watts each, so their load is negligible)

This setup provides a stable 11.8v under a 4 Amp load. I just ordered a second charger and will see how it performs with both chargers running at 4 Amps, right at the rated capacity of the Power Supply

[Spitball]

When I did the one someone begged offa me, I had used a twin-filament tail/brake light bulb and connected the heavy filament to the +3,3volt rail to load it and the lower current fialment to the +5volt rail - it also served as a nice amber pilot light and the output was about the same as yours - I saw the idea about two resistors but played around and found the trick with a tail light bulb worked just fine and it's not too bright; also runs a lot cooler. Must do another one for myself; every time I do one, some bugger begs it off me!

[moo]

Actually, the two wall warts, with a diode each in the positive line (or negative as long as the diodes are on the same wire) will work perfectly fine, as the current increases, the voltage decreases due to the internal resistance of the power supplies, this tends to even the load. You can plug in one at a time, no matter.

I used to do this with two $2200 lab power supplies, since we had them on hand and didn't want to spend $4k+ to replace them, big diodes are only $10 each. (I also had to change them over to 220Vac to get the kind of power we were drawing )(you can only draw ~1300W continuously from 110Vac x 15A x 80%)

[Gary Maker]

Personally I use a PC power supply that a friend rigged up for me to power my Triton charger and it works flawlessly.

If however, your not sure exactly what your doing, I would think for the price of one of your lipos you could buy a good commercial regulated 12v power supply and eliminate all worry and guess work along with having piece of mind, especially where charging lipos are concerned!

[Spitball]

Not as sure as you are Moo; it would be interesting to measure the individual currents and increase the load - might be a reasonable balance if the supplies were identical and transformer type - would hesitate to do this with switching supplies. Many of these actually increase slightly with load.
But with Lab Supplies I've worked with, you could interconnect the 'sense' terminals to properly 'load-share'?