I’ve had no issues with qo over the years for 12v except if they get dirt in them from mud dobber wasps.
Jay On Apr 26, 2024, at 9:05 AM, Darryl Thayer via RE-wrenches <re-wrenches@lists.re-wrenches.org> wrote:
I agree with John also. one of the better-performing off-grid houses I worked on used a 48 to 12-V Samlex converter. The 12-volt thick-walled refrigerator was about 4 amps at 12 volts. The lights, radio, and small TV drew very few amps each/ I also used an Outback 3648 inverter, which the homeowner turned on only. when needed (wash machine, etc.), I used SQ-D QO panel board in case the owner wanted to go to 120 volt AC future breaker panel. All lighting was Edison base lamps, and all wiring was NMB Romex. I wired like a normal house except for a 120-v panel and 12-v panel I relay and momentary switch by appliance for easy turning on of AC inverter. I agree with John.
Most 12v fridges have small compressors. But I don’t know what they have. Personally a major reason to go 120/ac is to get a normal refrigerator.
But you can measure the surge/load and then size the charger accordingly.
One feature of going charger is the lights are a lot brighter at night and last longer because they are not at 15v during the day.
Jay
Jason, I have a customer with the same situation except he already has a 12 V VFX inverter, He has a sunfrost fridge and other small loads with a very fancy custom control board originally set up to handle AC and DC systems. We are adding a lot more solar and I was considering a dual battery system but the owner didn't like that idea. We are going with and Iota 12v power supply (i use one at my house for my sunfrost) to power up all his DC loads and will be adding a large 48 V battery bank and over 4Kw of solar using a VFXR3648 directly in place of the 12V inverter. He complained that the existing inverter would not handle all his current AC loads very well. My own house is fully wired for 12VDC as well as AC (lots of #10 copper not being used) and I have been considering getting a small LFP 12V battery to put back on by DC System. Then use the Iota as a secondary charging method with some of my large stash of older modules hooked up for 12V direct with C40 charge controller to recreate my original system just for kicks. I'm only using DC for my Sunfrost and one "emergency light" in the livingroom right now. For your customer, a small LFP 12v battery (approximately $500 or less) to replace his old battery bankm and more larger ones for the new AC side with 48V inverter fed by his generator or through an Iota 48 V charger ifusing a smaller non charging inverter. Unlike Dave, I like these challenges. Maybe thats why I never seem to make money.!!
John Blittersdorf
Fortunately, the owner is pretty handy and is willing to live with any negative consequences. That said, I want to offer him something as simple and bulletproof as possible. I am walking into this with eyes wide open, for sure. 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
On 2024-04-23 2:40 pm, Jason Szumlanski via RE-wrenches 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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