[RE-wrenches] 120 Vac and 12Vdc mixed distribution system

[Jason Szumlanski]

Thanks, Jay. Any thoughts on whether a 100A 12V converter is adequate to handle
the startup surge of a modern 120V full-size refrigerator when an existing 400W
load is present? That would be my design parameters. 


I guess the other question is, what happens if the converter is overloaded? I
know they have overload protection, but what is the reset procedure?

Jason Szumlanski
Principal Solar Designer | Florida Solar Design Group
NABCEP Certified Solar Professional (PVIP)
Florida State Certified Solar Contractor CVC56956
Florida Certified Electrical Contractor EC13013208


[data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=3D]
On Tue, Apr 23, 2024 at 6:01 PM Jay via RE-wrenches
<re-wrenches at lists.re-wrenches.org> wrote:


> I’ve done this many times
> 
> I use an Iota or power max charger to run the DC.
> 
> Jay
> 
> > On Apr 23, 2024, at 2:42 PM, Jason Szumlanski via RE-wrenches
> <re-wrenches at lists.re-wrenches.org [re-wrenches at lists.re-wrenches.org]> wrote:
> >
> > 
> > I have an off-grid client who is working on replacing old equipment at a
> cabin. He has a lot of 12 volt distribution in the house for lighting, fans,
> and a 12 volt refrigerator. He also has 120 volt AC loads that run through a
> separate distribution panel where the only source is a 2000 Watt Honda
> generator. There is no inverter present. The batteries are charged through a
> Trace C40.
> >
> > He currently has a few ancient solar panels and a struggling Bank of AGM
> batteries. It's time for an upgrade. I can easily supply enough PV power for
> what he needs. He currently has a 9 kilowatt hour battery capacity that he was
> happy with when the batteries operated optimally. Nonetheless, I would
> probably future-proof him with a 10 to 15 kilowatt hour LiPo to double or
> triple his usable capacity.
> >
> > For convenience, obviously it would be nice to have an inverter to eliminate
> or reduce the generator requirement. But he seems committed to keeping his 12
> volt distribution because it would be costly to replace fixtures. I think he
> would consider replacing the 12 volt refrigerator if he has an inverter.
> >
> > He definitely wants LiPo batteries.
> >
> > I don't like the idea of 12 volt direct from a battery plus connecting an
> inverter to that same battery. It is going to be hard to measure and monitor
> things.
> >
> > I am thinking about using a 48 volt battery with a single phase 120 volt
> inverter, getting him to change to a 120 volt refrigerator, and using a DC
> converter to give him somewhere in the range of 100 amps at 12 volts for his
> existing DC lighting and fan loads. Is this a bad idea? Should I stick with a
> 12 volt battery system? He does have a tiny 12 volt pressure pump which might
> be an issue for the converter. I'm not sure. I am a bit worried about the
> efficiency loss and capacity of DC converters and not sure how to size it.
> >
> > Jason Szumlanski
> > Florida Solar Design Group
> >
> >
> >
> >
> >
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