I've got 400 V DC, 4 kW from solar & would like 13 V DC @ about 100 A or 120 V AC 60 Hz output. Just more $ than I want to part with & my ambition is shot.

 

Where is the 400 VDC 4 KW going now?

 

If you want 60hz AC, you are going to need to make an inverter, whats the 400V doing?

 

350 to 370 volts DC is the standard upper limit of most power supplies. Three phase 480 input types can go as high as 750 volts DC.

I found a 1000 watt 12 volt power supply that tops out at 300 VDC.

Can you split the string of panels to get 200 volts? Two of these running with 200 DC should take care of your 12 volt needs.

http://www.mouser.com/Search/m_Prod...Ps3th5F8koKFZNZ71yY1F2EiHOy/qFktw71t5amchNg==

 

The 4 kW solar ( 5.5 kW rated ) is grid tied & keeps me cool in the summer while I pay my $ 11. electric bill monthly & collect about $ 90 credit every October. Playing the what if card I've collected some large E cores
& a pair of 400 A, 45 V shottky diodes. I already have a 2 kW 12 to 120 V AC invertor from long gone motor home.

 

The 4 kW solar ( 5.5 kW rated ) is grid tied & keeps me cool in the summer while I pay my $ 11. electric bill monthly & collect about $ 90 credit every October. Playing the what if card I've collected some large E cores
& a pair of 400 A, 45 V shottky diodes. I already have a 2 kW 12 to 120 V AC invertor from long gone motor home.

Then you have no justifiable gains to take the 400 VDC and reduce it down to 12 VDC with a dedicated converter when you already have an active 120/240 VAC source being fed by the solar power through your grid tie inverter system that nay common transformer or SMPS based step down power unit can plug into.
Thanks to your grid tie inverter your 400 VDC solar power is already available in your walls for free as your 120/240 VAC power whenever the system is active.

Simply put, the elimination of one conversion step will not get you enough of an efficiency gain to justify the cost of buying or custom building a 400 VDC to 12 VDC 100 amp converter unit.