How to make two isolated power sources from one source

automotivebattery-chargingchargerisolationpower supply

I need to have two electrically isolated power sources.

Here are the details of the application: http://revolectrix.fmadirect.com/support_docs/item_1377.pdf page 26:

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I need to make this work with a car 12V DC installation as the only power source. This should work with a current up to 70 A (max of my car alternator).

Is there something I can attach to the car's 12V installation to make two isolated power sources out of it, to power these two FMA Cellpro Powerlab 8 units?

Clarification: the isolation of the power supplies is required because the two battery-charging devices connected to them are connected to each other in series, so the (+) terminal of the first one is connected to the (-) terminal of the second one. If the power supplies would not be isolated, then they would have common (-) and effectively the (+) and (-) terminals of the first device would be shorted.

Best Answer

There's no way I'm reading all that PDF to find out what you need the power supplies to do. Please summarize it for those of us that don't need to know all the details of your project just to advise you on one part of it.

However, that said, here's my immediate thoughts:

  1. The only way to properly isolate a power output from its source (and hence from any other power output on the same source) is with a transformer.

  2. The only way to use a transformer is with AC.

So, if you can generate an AC wave form with enough current capacity to do what you require, you can use that to drive a transformer, which you can then rectify/smooth/etc the output of. This could be a multi-tap transformer to give you multiple outputs, or it could be a two single tap ones.

Of course, if you don't require 100% isolation, then there are other options. Two switched-mode power circuits running off one feed will give a certain level of isolation between the two circuits. It all depends if you require complete isolation, or just enough such that over-current on one output can't cause a voltage drop on the other output.

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