Paralleling Power Supply Units Made Easy ???

ken white wrote:
When paralleling 2 supplies that are not designed to be paralleled together, you are effectively injecting a dynamic disturbance into each supply's independent feedback control loop.

The gain/phase margin around this disturbance loop is quite different so instability could become an issue.

Ken,

You're right on with this comment - however many outside of the electrical engineeing world will have no idea what this means.

I'm well aware of feedback loop theory and practice, but completely ignored it a few years ago in our RV and went for broke. Our RV has a good old Parallax converter in it which has been rock solid for years. To speed up drycamp charging a bit, I took an old Sears 2/10/50 charger and tried paralleling it with the Parallax. I set the Sears to it's 50 amp "engine start" position and watched the current flow from it to make sure it wasn't high enough to destroy itself after too many minutes. The Sears contributed about 50% more to the converter alone's charging current and was well below what would burn up the Sears on it's meant-for-short-term-use-only 50 amp engine start setting.

These two power supplies - just by pure luck - work well together for dumping more current into the RV's AGM batteries while the genny is running. Of course I didn't look with an o'scope for oscillations, because a couple of 100 AH batteries as a load (acting as a huge capacitor) pretty much dampens out instability oscillations at any frequencies of concern.

I got the idea to "just try" the multiple power supplies in parallel from pianotuna - who I believe had started using this approach in his RV for battery charging many years ago with good results.