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jb802
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# Posted: 8 May 2024 03:11pm
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Looking for suggestions regarding efficient utilization of two wiring set ups, 120 & 12v, that were pre existing in the cabin we purchased in northern Vermont.
Here are some details:
1. Gas generator powers cabin (120) which we use for tools, mostly
2. The cabin has 12 Volt wiring too evidenced by different outlets (photos below), switches, wiring and 12 volt fixtures in the cabin and an old 12v water pump
3. The 12volt battery (auto) appeared to be wired to genny power so when the generator was on, the battery would stay charged (I think?)
Ideally we'd like to use the 12volt system to flip a switch on in the hallway or in the bathroom when it's dark (right now we use portable solar lights) and have the 12volt power a water pump, maybe a fan at night.
Can we integrate (or are they already) these two systems seamlessly? Or, do we just connect the 12volt system to a tiny solar panel and figure out which fixtures are wired 12v and run the genny for tool power and recharging in a pinch, essentially leaving the two systems working in parallel fashion? Any suggestions?
Thanks!
JB
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Brettny
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# Posted: 8 May 2024 08:22pm
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You just need a inverter to power your 120v lighting and outlets. Size and other features are determined by your needs and battery size.
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gcrank1
Member
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# Posted: 9 May 2024 12:55am - Edited by: gcrank1
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Ime using the 12vdc taps on the gen to charge a battery is far from ideal. If that is what you have get an automotive charger with some real output plugged into the 120vac on the gen.
An automotive 'starting' battery is the wrong bat to use in anything other than a last ditch stand.
Given you are in N Vermont with winter freezing temps I can't recommend the LFP batteries, you would be better off with a 12v 100ah 'deep cycle/marine (trolling motor)/rv lead acid battery. 2 hooked up in parallel would be even better.
Another option would be to use 2 of the 6v 'golf cart' batteries hooked up in series to make them a 12v.
Btw, LFP bats would be fine for above freezing temps but you might want to get some 'basic' battery experience before jumping into the high buck bats.
With good bat(s) you can find out if you are getting the kind of use/performance from your 12dc system to suit your needs (and it is already wired for it). Some folks like having the simple 12v for basic needs.
At one time I did too, then I had a split 120vac/12v then gave up the 12v and did as Brett suggests, use an inverter off the 12 bat(s) to make it all 120vac. That really simplified my life, ymmv. Thing is, with a good 12v battery 'power base' you can always grow into the inverter.
Advantage for us with the 12v and inverter is that we can run everything that is low draw (most stuff; ie, lights, TV/dvd, fans, tool bat chargers, any usb chargers, even a toaster) off a quiet battery and only use the gen for big power tools, microwave, etc And whenever the gen runs have that charger pumping amps back into the bat-bank.
Solar can come later once you have all this working.
Oh, costs? 2 12v/100ah deep cycle bats from Walmart are about $100-$125 each, some good heavy gauge cables to parallel them, maybe some DC fusing (is there any now?).
A good automotive min.20a charger is $? I suggest the new-gen smart chargers.
If you choose to get an inverter at some point we should talk about that separate 
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toyota_mdt_tech
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# Posted: 9 May 2024 01:13am
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Quoting: Brettny You just need a inverter to power your 120v lighting and outlets. Size and other features are determined by your needs and battery size.
Bingo, scrap 12V, use 12VDC to 120VAC inverter to make 120VAC and run AC circuits like home.
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ICC
Member
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# Posted: 9 May 2024 01:15am
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Auto batteries belong in a vehicle and never for use in a cabin power system. I prefer 2 x 6 volt golf cart batteries for simple 12 volts.
As gcrank1 states, maybe forget LFP until you have learned more about handling batteries. LFP have critical "must-not-do" things.
To charge a battery from a generator you need a good (multi-stage smart charger) battery charger made to charge lead-acid batteries (or LFP). Again, as grank1 stated the 12-volt line feeds on a generator are not really meant for serious battery charging.
Fuses (or breakers)... Yes, fuses are safety devices. They are used t protect the wiring from melting or burning.
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gcrank1
Member
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# Posted: 9 May 2024 03:13am
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Something not mentioned thus far...the wire gauge used (as in your pic) looks too small for dc to me unless the runs are very short. You have 'line losses' to consider for the dc power required by a device at the end. The lower the voltage the bigger the wires need to be, that is another reason I went 120vac from inverter, much longer runs with std 14/2 w grd Romex for 15a circuits.
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Brettny
Member
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# Posted: 9 May 2024 01:10pm
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Quoting: toyota_mdt_tech Bingo, scrap 12V, use 12VDC to 120VAC inverter to make 120VAC and run AC circuits like home.
I figure by the time I buy all the 12v wireing, breakers, appliances, lights, switches I could have just added a bit more battery capacity and ran standard 120v stuff. Halfway through my cabin wireing I decided to scrap all the 12v stuff becids a USB and cig lighter plug in each bedroom.
120v lights, fridge, water pump and 120v control circuit on our propane water heater. All standard stuff I can easily find at a big box store.
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jb802
Member
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# Posted: 10 May 2024 05:17am
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Copy on all of that. Thank you, very informative. Seems like prevailing sentiment is going 120 off 12v via inverter but trying to work w/ 12v system in short term. We'll do that as it is wired to see what it can do. We do have an 18watt panel that can keep bats topped up. Definitely looking for simplicity.
Regarding the wiring gauge, that is good intel, did not know that.
I appreciate all the feedback, thank you! Will return with some updates, hopefully soon!
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gcrank1
Member
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# Posted: 10 May 2024 11:41am
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An 18W solar panel will not keep a 12v battery (of the size needed for a cabin) charged up. That is a size used as a 'trickle charger'/battery maintainer; ie, to keep a fully charged battery charged in a storage/non-use situation.
Example: a 100ah battery needs about 200w of solar array to recover from a typical day's power use. And more is better. Depending upon location you only get about 4 hrs of good solar, 10am-2pm, on good days.
A common mistake is underestimating one's power use and overestimating the solar recharging.
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Brettny
Member
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# Posted: 10 May 2024 12:37pm
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Ard there also 120v lights in your cabin? I take it theres no lighting at the moment becids what's shown(120v). If so just buy a solar generator and plug it into your 12pv feed line. It's going to be the simplest and most fool proof option.
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paulz
Member
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# Posted: 11 May 2024 05:49pm
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I’m still running 12v mainly, use inverter sporadically for toaster, nuker, skill saw, washing machine. 12v LED lighting, water pump, TV, modem, fridge. After reading this maybe I will switch at least the pump and fridge over to 110 when they quit.
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