# RFC - 10A DC to DC voltage multipler/doubler

Thread Starter

#### sonnyboy

Joined Jun 26, 2007
3
I am designing a solar generation plant and can save several hundred dollars by purchasing a larger inverter - and doubling the voltage from my solar panels. I need to be able to double 162VDC at 10A. Most of my searches via the net have found low volatge/amperage circuits.

I am open to sugeestions for or against this idea, and if an inexpensive soultion is available - I am eager to build it.

Thanks

#### lightingman

Joined Apr 19, 2007
374
Hi...There will be no inexpensive soultion to this one....You are looking at high voltage, high current and DC.....This means some sort of inverter, and a lot of work to design and build....But you never know.... someone out ther may have already done it....Good luck..Daniel.

#### recca02

Joined Apr 2, 2007
1,214
what purpose does doubling the voltage serve (increase the max power that can be stored?)
if thats the case will inverters in parallel not help?

#### kubeek

Joined Sep 20, 2005
5,757
I thought that solar plants use inverters to convert DC to AC, so why you need the doubling?

#### John Luciani

Joined Apr 3, 2007
477
I am designing a solar generation plant and can save several hundred dollars by purchasing a larger inverter - and doubling the voltage from my solar panels. I need to be able to double 162VDC at 10A. Most of my searches via the net have found low volatge/amperage circuits.

I am open to sugeestions for or against this idea, and if an inexpensive soultion is available - I am eager to build it.
You're not going to find a 1.6KW DC-DC converter for a few hundred dollars.

Also don't forget the losses in the conversion. The DC-DC conversion will probably
have an efficiency of 80-85% at best.

(* jcl *)

Thread Starter

#### sonnyboy

Joined Jun 26, 2007
3
Thanks for the replies.

My original solar plant design was a 1.1KW inverter and 7 panels. I plan to add panels after the intial install. I wanted to double the voltage from the panels to allow me to start a 2kW inverter (using only 50% theoretical generation) and later add panels to use the full 2kW. By using a 2kW inverter from the start I would not have to buy a second one later, when I had added more panels.

It is actually cheaper to buy the 2kW inverter (400$U.S. cheaper) than the 1.1kW model. In honesty, the inverters are cheap, the panels are not! From what I'm seeing in the posts it looks as though this may not be a good idea. #### John Luciani Joined Apr 3, 2007 477 Thanks for the replies. My original solar plant design was a 1.1KW inverter and 7 panels. I plan to add panels after the intial install. I wanted to double the voltage from the panels to allow me to start a 2kW inverter (using only 50% theoretical generation) and later add panels to use the full 2kW. By using a 2kW inverter from the start I would not have to buy a second one later, when I had added more panels. It is actually cheaper to buy the 2kW inverter (400$ U.S. cheaper) than the 1.1kW model. In honesty, the inverters are cheap, the panels are not!

From what I'm seeing in the posts it looks as though this may not be a good idea.
Are you sure that the 2KW inverter requires double the voltage and not double
the current? Sometimes multiple voltage sources are diode or'ed together.

(* jcl *)

Thread Starter

#### sonnyboy

Joined Jun 26, 2007
3
JCL-

Yes I am sure about the voltage - this model of inverter requires the solar panels to be connected in parallel, thus stacking the voltage output but producing a stable current (7-8A per panel). The 1.1 and 1.8 kW models have a "start" voltage of 180VDC. Granted I stated 162V, but this is the operational output of the combined panels, not the open voltage and falls in the maximum power tracking range of the smaller inverters. I surmise the open voltage will be closer to 200V(my existing test panel has an open voltage of 23VDC, but operational of 18VDC). The 2kW model requires a start voltage above 220VDC. Hence my plan was to trick the larger inverter into starting the AC output with 1180W of panels to drive it.

To put a dollar figure on it - if I buy the 2kW and the panels to drive it, my project cost exceeds $12K USD, versus$6K to get online with a 1.1kW inverter and 6 175W panels, but as I add panels in the future I will then have to purchase a new inverter....

#### John Luciani

Joined Apr 3, 2007
477
JCL-

The 1.1 and 1.8 kW models have a "start" voltage of 180VDC. Granted I stated 162V, but this is the operational output of the combined panels, not the open voltage and falls in the maximum power tracking range of the smaller inverters. I surmise the open voltage will be closer to 200V(my existing test panel has an open voltage of 23VDC, but operational of 18VDC). The 2kW model requires a start voltage above 220VDC. Hence my plan was to trick the larger inverter into starting the AC output with 1180W of panels to drive it.
Going from 180VDC to 220VDC may be easier than doubling.

Here is my half-baked idea -- run the panel output (162VDC) into an *isolated*
DC-DC converter that generates 48VDC (which is a standard telecom voltage).
Connect the series combination of the DC-DC output and the solar panel output
to the inverter.

The voltage/current/power numbers may not workout. Also, IIRC your current is 6A. So
you would need a 300W converter which will probably cost a few hundred USD.

(* jcl *)

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