Yet another GT workaround question

Re: Yet another GT workaround question

techntrek wrote: »

jagec, how about forgetting the shunt controller and 48-to-12 converter, instead use high-voltage DC-DC controllers. Vicor has a line of converters that can take up to 425 volts input and drop it anywhere in the 2-50 volt range at 600 watts. They are designed to be paralleled for increased power handling (each unit has a pin you tie together between units to ensure they share the load equally). They can be found for a song on Ebay if you keep an eye out.

http://www.vicr.com/cms/home/products/brick/mini-maxi-micro-converters

That's an interesting thought. I looked up some of the specs on the Vicor products, and the ebay units do seem remarkably cheap for what you get.

Of course, you'd have to get one that was >15V, otherwise the downstream charge controller wouldn't be able to equalize the batteries. Furthermore, if the charge controller tried to pull more current than the array could produce (clouds or the like), the voltage collapse would cause the Vicor to disconnect and interrupt charging.

But, assuming that charger demands remain below the array's ability to provide (which would usually be the case), this would be easier to manage than connecting dump loads in series, and the current multiplier effect would allow for better charge rates on the batteries.

So, $40 for the Vicor, $70-150 for a PWM charge controller, $100-200 for a cheap MSW inverter, and $200-500 for batteries, plus some wiring, switches, and fuses. The generator is still the better option, but it would keep the lights on for a lot cheaper than a true hybrid system.

As for the series dump load idea, the costs would be similar, except that you'd be buying low-cost dump loads instead of the Vicor, a lower-amperage charge controller, and fewer batteries, for a much smaller storage capacity at probably half the cost. But assuming that your dump loads are at all useful, this method gets the most out of the array WHEN the sun is shining.

For a straight-up shunt controller with no series dump loads, the costs would work out about the same as with series dump loads, except for a greater sensitivity to component failure and an almost total waste of array power.