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Is it possible to get a DC DC converter which the output voltage varies proportionally to the input voltage? ie 14V in 28V out, 13.4V in 26.8V out.

To add some context I wish to charge a 24V battery system and use it to provide power to a 1.1Kw (1.5HP) 24V motor.

In this case charge would come from a wind turbine controller with a 12V output with a current between 100mA and 1.5A. Obviously the voltage would be greater than 12V in order to charge a battery and this is where my question comes from. If i was to use a 12VDC - 24VDC converter could it provide a charge to the 24V battery bank.

I'm open to suggestions, if you can envisage a better way then please let me know.

Thanks

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  • \$\begingroup\$ Do you want to buy one or make one? If you buy, I doubt you'll find one with zero line regulation because most people want a specific output regardless of line or load variations. If you make, then you can either redesign the feedback to make it do what you want or simply omit it and tune the oscillator itself for the correct ratio under "typical" conditions. \$\endgroup\$ – AaronD Jan 22 '15 at 20:15
  • \$\begingroup\$ Why can't you just use a regular voltage regulator? If the battery has a 26V charging voltage, just slap a 26V regulator in there. Am I missing something? \$\endgroup\$ – I. Wolfe Jan 22 '15 at 20:39
  • \$\begingroup\$ Your turbine is <20W and your motor is 1.1Kw - I hope you're not expecting to run it very often.. \$\endgroup\$ – pjc50 Jan 22 '15 at 20:43
  • \$\begingroup\$ @AaronD I was looking to buy one preferably. Thanks for your ideas. \$\endgroup\$ – AdamC Jan 22 '15 at 22:22
  • \$\begingroup\$ @I.Wolfe The charging Voltage will vary depending on state of the battery such as boost or float and as Dave Tweed points out the charge controller needs a feed back loop to regulate the correct charging voltage. Unless i'm missing something? Thanks for your ideas. \$\endgroup\$ – AdamC Jan 22 '15 at 22:27
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Yes, Vicor, for example, makes a line of such converters, typically used for point-of-load conversion from a regulated high voltage (e.g., a 48V distribution bus) to a low-voltage, high-current supply for a CPU. (Note the option for "fixed ratio" under "Output Voltage".)

You could easily construct a boost converter that has the same property. In fact, any continuous conduction mode switched converter (buck or boost) operating with a fixed duty cycle has this property.

But such a converter would not be particularly useful in terms of using a 12V battery charger to charge a 24V battery pack. The converter would prevent the charger from getting any feedback about the state of the battery, leading to overcharging.

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  • \$\begingroup\$ Thanks for the answer. Its a very good point about the lack of a feedback loop for the charge controller, looks like i just have to have a 24V charge controller for the turbine. \$\endgroup\$ – AdamC Jan 22 '15 at 22:31

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