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Small Cabin Forum / Off-Grid Living / Wiring between 3 locations at the cabin, would 1 system or multiple systems be better?
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# Posted: 16 Jul 2021 01:15

Quoting: Daaaaaaaan
If we're running off lead-acid batteries, we'll be running closer to 13V when fully charged. Maybe a bit higher when solar is on. You'll only see 12V when deeply discharged.

I am and they register about 13.5 in the day and we try to cut off around 12.7-12.5 at night.

I will take the volt meter and check it tomorrow when I'm up there but it is for sure running without issues all week. It will be cloudy/rainy tomorrow so I will see how that works. Ideally I would like to not have to run AC up there because I figured it would lose more going DC->AC->DC

GPM is 100% better than gravity fed and at this point I cant see a difference running a 12v generator vs running off the batteries at a 115' run of 12/2. I can also do a test on that with a large bucket to see the output but I think the L5 ecotemp hot water (1.5 GPM) can not actually keep up to the shurflo (3gpm).

So even if the shurflo is going slightly less I doubt its 50% less.

So now we have one person saying it wont burn out and a few saying it will... ;)

# Posted: 16 Jul 2021 09:28

Are you doing that bat cut-off at 12.7-12.5 when that is a resting voltage? If that is under load or soon after the bats havent had time to self-recover and actually have more charge; ie, more juice to use.
Of course, if your pattern of use is working with the way you are doing it that is fine. We have been just using our system without much thought to conservation to see how it works without active management, and it is chugging along. I do monitor the readouts through the day to have a feel for what is going on.

# Posted: 16 Jul 2021 11:03 - Edited by: smokedvw

Quoting: gcrank1
Are you doing that bat cut-off at 12.7-12.5 when that is a resting voltage? If that is under load or soon after the bats havent had time to self-recover and actually have more charge; ie, more juice to use.

Right now we are really just basing this on the light in the day and how its reacting to the load.


1 - Longi 305W 60 Cell Full Silver Frame 40m
1 - Victron 100/30A MPTT Charge Controller
1 - Noname 1000W pure sin inverter
2 - Costco 6V 205 AH lead acid batteries setup as 12v. The guy at the solar place said the costco ones are not great and dont last long but well see I guess. $50 more to go to Rolls vs Costco.

- 7amp shurflo pump (running on DC 115' on 12/2 line but I will update it to 120V then swap back to 12v DC this weekend since everyone seems to be gung ho on that approach here)
- 4 internal cabin lights (setup this weekend) running at 7w
- 1 cell phone charger

Daily heavier loads (can be swapped to generator on crap days) - typically turned on at 9 to 10am
- apartment sized fridge 4/2amp at 120v (480w/240w) draw), ive seen it on the charge controller as low as 2-3 amp readout when running and 12-15 when starting up
- ice machine 2amp @ 120v, 240w, took 350 watts yesterday on 120v system at home to make 3 sets of ice so well see how it does

My plan has been to not drop the battery below 12.2v. So far that means through the day as long as their is sun we just cut it off just before the last bit of sun hits the panel at 8pm. Then we run the generator for a hour from 8 to 9. I am going to setup a battery charger form the generator to the batteries to run at that time period this weekend as well and if its a cloudy day out we can use that to charge as well.

So far its working and I'm surprised we can get off gas and just run the solar all day for those loads. We ordered a new propane fridge, everything is massively on backorder but I will continue using this setup when I am there vs my parents will move to the propane fridge 24/7.

We do get solar from sun up to about 9pm currently but I do not think the panel is directly at solar noon so I'm going to adjust it this weekend too. Its about 2 hours off I would suspect based on calculating solar noon last week.

Gcrank how far down do you let your batteries run? What got me scared is how rapidly the lead acid deteriorate once you get them going past 50% over a 5 year period.

How old are your batteries now and do you see a big difference from new?

# Posted: 16 Jul 2021 11:59

LA want to be kept charged. Any depletion from over night (or day before) needs to be put back in asap the next day. I have my primary array pointed E/SE and my two 10yr old LA bats typically recharge by noon. Our morning elec needs are minimal so basically whatever is turned on runs off the array while the bats recharge. If needed I would run the gen c/w my 20amp ac battery charger. Note that the charge back into the bats needs to be within the mfr 'C' rating.
After I lose much of my sun post 1pm, if we are running the big fan, I can see my voltmeter slowly drop through the late aft 'under load'. If I stop it when reading 12.4 and check an hour later my bats have settled back at 12.8-12.9; ie, still fully charged for the evening use. pretty much ideal, thinks I, for Our Usage. My target was to use no more than 30% of charge with 50% being an extreme rare case. I think Im doing better than that. Overnight the usage is slim and after bedtime pretty much -0-. Energy conservation is our friend; we gave up on trying to run a dorm fridge/energy hog and the Yeti clone ice chest works great, but we are not there full time.
Imo, you want enough array to have the recharge happen soon in am, and tailor your usage to be using excess solar beyond recharge needs, or up the array to do so, during the day. If you have to be running the gen to keep the bats charged after a good sun day you dont have enough array and/or it is configured wrong. (Btw, Im running panels in series/parallel, 24v into the mppt scc into 12v bat-bank). I believe the mppt is an advantage to me over pwm. Even a little bit, or another way, Every Little Bit Extra is an advantage.
Short is, if you are not having enough bat power to run everything you want to run you need more bats Or change your use patterns Or Use Less.
If you have more bats you need more array to feed them so they recharge by noonish. If your inadequate array takes all of a good solar day to recharge them you cant run other stuff during the day because you need everything to charge; ie, there effectively is no 'excess'. That makes your LA batteries work way too hard and die young.

# Posted: 16 Jul 2021 12:31

Sounds good.

Yeah they are typically full charged by sometime before noon with the load on them. I'll be setting up a tower fan this week too so we'll see. I might need to get a more economical one if it draws to much.

# Posted: 16 Jul 2021 20:41

12.49v at pump not running
10.5v running

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