200v-12v DCDC buck converter

[MachOne]

Hi folks. I currently have a 5kW grid tie system that has 2 strings, one is ~170v the other ~260v. Obviously the system is useless during a power outage due to the grid tie inverter. We are experiencing more severe weather events and subsequent outages. I was looking at ways of using the panels if the outage dragged on, but can't afford a hybrid inverter setup. I have a 100Ah 4s LiFePo4 pack that I can use, and was looking for a way to charge this using the panels, which I could disconnect from the inverter if the outage was going to go on for days. I really only need to keep the fridge/freezer running and maybe charge a few small devices.

So I'm looking for a DCDC converter that could power my hobby charger. The only one I can find so far that can handle the 170v input is the Kelly KL-144DCDC-400-5 https://kellycontroller.com/shop/kelly-dcdc-converter/ It could actually charge the battery directly at 13.5v, but not to full capacity.

Are there any other converters that could do this? The charger can handle ~11-18v, and I'd like to charge at 20amps or so. I've read that a standard mains AC switching converter could work, but I don't think my panel voltages line up to either a 120v or 240v unit.

Thanks for any input.

(I am aware of the risks of high voltage DC and would isolate panels and take appropriate precautions where needed.)

 

[rmaddy]

Normally a solar charge controller is used to charge a battery with solar panels. You could get an appropriately sized MPPT SCC and hook it up to the LiFePO4 batteries. Put an appropriate selector switch on the PV wires so you can switch between the grid tie system and the stand-alone SCC. Then you can connect to the battery whatever DC loads are needed.

 

[MachOne]

Normally a solar charge controller is used to charge a battery with solar panels. You could get an appropriately sized MPPT SCC and hook it up to the LiFePO4 batteries. Put an appropriate selector switch on the PV wires so you can switch between the grid tie system and the stand-alone SCC. Then you can connect to the battery whatever DC loads are needed.

I'm having trouble finding a 200v input charge controller that doesn't cost a considerable sum of money. The attraction of the Kelly is that I can afford it and an inverter to power the fridge. I should have mentioned the very limited budget of a few hundred $. Given that it will only be used in the rare event of a prolonged power outage (maybe once every 10 years, maybe more when climate change really kicks in) I'm happy to manage it manually.

Maybe there's something I'm overlooking re using the Kelly in this application though. I guess it will just shut down if the voltage drops too low?

 

[rmaddy]

Given that it will only be used in the rare event of a prolonged power outage (maybe once every 10 years

For such a rare use get a simple gas/diesel powered generator. You don't want a LiFePO4 battery (or any battery) sitting around unused for a decade waiting for the rare event.

And consider that these rare events are typically bad for solar (rain, clouds, snow, destructive winds).

 

[MachOne]

For such a rare use get a simple gas/diesel powered generator. You don't want a LiFePO4 battery (or any battery) sitting around unused for a decade waiting for the rare event.

I was considering a generator, but don't really want to have to deal with storing gas, running anually to test then emptying carb etc. for storage. The battery gets used for other things so that's not an issue. The panels should be plenty even in overcast conditions to supply enough charge to run the fridge for a few hours each day. Thanks for the ideas

 

[Bvillebob]

That's where a propane powered generator is perfect. Store a bottle of propane, which will keep for many years and you're good to go. Don't have the issues of fuel going bad and carbuerators getting gunked up. Or, find a Midnite Classic 200 or 250 charge controller.