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gcrank1
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# Posted: 11 Feb 2021 06:48pm - Edited by: gcrank1
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Its deep winter in WI so Im thinkin and calculatin about my 12v solar system. Im not changing voltage or buying new or more panels, etc (but battery(s) yes), Im trying to get this equipment to produce as best it can.
Basically all my loads are inverted to 120vac.
A .2amp 120v load will still be 2amps + from the bat-bank. The + because of inverter inefficiency, etc.
A .5amp @ 120 will be 5amps +, both examples make good multipliers for whatever loads need calculatin'.
Now, adding up my light duty usage, some LEDs, usb ports, low-amp cig-lighter socket, occasional/limited ceiling fan on low I can get that .5a @ 120v/5a + off the bat pretty easy. That aint much, yet it is a lot.
Here is what Im figuring:
5a over an average of 16hrs out of a 24hr day = 80ah.
80ah is what I can safely draw off a 100ah LFP battery in 1 day. That bat Im looking at is about $600.
If I want that oft mentioned 3 day buffer supply of ah's that would be a 300ah LFP bat-bank at about $1800.
In reality 10amps per hour would be a MUCH more desirable capability, that would be one day = 160ah's requiring 200ah LFP ($1100ish) or 3 days 600ahs @ $3300. All for ONLY 10amp/hr over 16hrs/day.
(15amps per hour way better (240ah's), do the math)
And these are just the battery costs (Ive got the rest but a newbie thinking they want solar will buy it ALL)
Am I wrong/not getting something?
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BobW
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# Posted: 11 Feb 2021 07:17pm
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The highest electric bill ever on the place in Tennessee was $100.00. Most months it is much less and only $30.00 when not there. No electric bill would save no more than $600.00 a year and likely less. I figure at my age the pay off would come sometime after I become the oldest person in the world.
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Brettny
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# Posted: 11 Feb 2021 07:47pm
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Have you priced out your AH needs in a golf cart battery? At $3300 for batteries a $200 1kw sportsman inverter with a $130 30a rv charger is looking prety good...it can add to your capacity or you can lower your AH on your bank.
My 1kw inverter burns 0.5gal of fuel in no less than 8hrs.
Also you could shut off the ceiling fan and charge the rest of the stuff off a portable battery bank that are prety affordable.
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gcrank1
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# Posted: 12 Feb 2021 12:06am - Edited by: gcrank1
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GC vs LFP, yep Brett, you make a good point.
A 100ah LFP usable ah's equals about 3 100ah 'marine' FLA , that offsets a lot of the cost, or to look at it differently, 3 less efficient and cost effective FLPs are needed to replace one smaller and lighter LFP.
GCs are 6v x 200-225ish ah, 2/s = 12v x 200-225ah with 60-68ish ah available at 25-30% dod
Or, because they can take deep discharge better than marine bats, at 50% they can dump 100-112ah's.
Yes, a viable alternative, more affordable now certainly, and better bang for the buck that 'marine deep cycle'. They may even last long enough to be all I 'need'; ie, will I still be doing this in another 5 years.
BobW, if I didnt get all this solar setup with the place, basically a throw-in for free, I wouldnt be buying it all.
Most likely Id be running off my Lil' Champ 1700/2000w inv/gen for big stuff (like I do now) and a 100ah LFP 12v that Id take home and back each trip. That is relatively quick and easy to set up for a newby. How one charges a battery after that becomes the 'solar or not' question, the battery doesnt care just so it gets charged. But it will never make Real Power no matter how big an inverter is stuck on it (imo, too big an inv is a common newby mistake).
If the prev owner had done grid years back Id be gladly paying the monthly $35ish bill.
It would be likely grid to an RV-Ped and have Real Power.
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Steve_S
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# Posted: 12 Feb 2021 04:23am
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Get a quote from your local power co for what it will cost to run wires, poles and meter etc THEN ponder it.
There is Deep Cycle Lead for a good reason, they are not Golf Cart Batteries or such and they are expensive but they are intended for the purpose. AND they need care and attention +++
LFP may be more expensive at first blush but when you crunch the numbers it isn't. Amp Hours per Dollar X number of serviceable years.
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gcrank1
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# Posted: 12 Feb 2021 04:47am - Edited by: gcrank1
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Yes, proceed with knowledge rather than speculation.
Power co. says I have to have a building permit before they will come est. the run (all underground now).
Township says $350 for permit
Power co says $50 non-refundable to do est.
$400 cost for the knowledge only. Fwiw, from talking to a couple of folks last summer up there who recently put power in it looks like about $3K, but with my longer run in at a per foot price I may be closer to $5K.
That hurts.
Ive got available a new RhinoVoltz 100ah LFP 1 hr drive away for under $600. Easily 80ah net usable. The Rhino is so tempting...I like stuff that lasts long and is more cost effective. It looks like the GC2s are the low-end of FLA 'acceptable for the purpose'...the high-end ones are mighty close to LFP.
But (and what my orig post is about), Id still have the 'about 5amps/hr' limitation for continuous draw down. No way around that unless going BIG.
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Brettny
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# Posted: 12 Feb 2021 06:02am
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Quoting: gcrank1 I like stuff that lasts long and is more cost effective.
Grid power lasts longer than any solar setup. I wasn't aware grid power was available. At $5k put in the grid power.
I spent $1200 on my system and bought some used components. If grid power was $5k away I would be getting grid power. The closest power line isnt even on my road and at least 3/4mi away.
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Nate R
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# Posted: 12 Feb 2021 10:12am
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Yeah, I spent about $3k to get grid power, basically. While I'm now on the hook for the $21/mo minimum, I'd also have to replace off-grid parts over time, too. I'd spend the 3-5K and get grid power.
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jhp
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# Posted: 12 Feb 2021 10:48am - Edited by: jhp
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The power company can give you the rough price to install the basic service and a per foot charge for the wiring.
My power company charges about $1500 to drop the transformer and the base in your yard, $5 a foot (underground) for the first 300' and $2.75 a foot for anything over that. When I measured myself from the nearest power pole and estimated the charge it was within a few tens of dollars of what it actually cost.
Overhead as I recall was maybe half that (just the wiring charge) but I didn't want to take trees down to bring in power.
The last thing, pretty much every dollar you put into bringing in grid power goes right into the value of the property. $3,000 to bring in grid power goes right to your bottom line...$3,000 on a nice solar setup is a sunk cost and worth basically nothing long term.
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ICC
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# Posted: 12 Feb 2021 10:52am
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I agree, if grid power is available for 3 to 5 K, I would go grid connected, IF the grid was reliable. I have friends who are grid connected in the boonies and they have outages several times a year, sometimes lasting a day. In my case it was a nobrainer to go solar. The power company had an estimate of 65K.
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snobdds
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# Posted: 12 Feb 2021 10:57am - Edited by: snobdds
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There is no reason to build any systems anymore. The market has solved that problem for us. This little guy is all set up and ready. Has more than enough power for a cabin and lasts for days. Can be charged via solar or a generator if the sun is not out. Has over 5000 cycles in it and it's Lifepo4 battery, which is a lot safer than lithium. It even has a underwriting laboratories seal of approval for those of us that have cabin insurance. For less than $2,000, you can have a system that others have spent 5,000 to get the same thing. Plue it more user friendly.
https://www.bluetti.com/products/bluetti-ac200p-2000wh-2000w-portable-power-station
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gcrank1
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# Posted: 12 Feb 2021 12:25pm - Edited by: gcrank1
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Hmmm, that is slick.
$2000 pretty much all in ready to rock.
MC-4 array con, looks like it must have its own scc internal and you plug&play the array; no special adapter needed; cool.
Inc the car chgr and 120vac wall chgr, cool.
No charger(s) to buy!
2KW, so at 12v it must be about a 150ah LFP battery, though in my quick read I did not find that spec.
If so, then I would shoot for 120ish ah's usable for max cycles/bat health. Decent for my use.
60ish #; cool.
Neat,,tidy, attractive...no muss, no fuss; cool.
Compare with:
RhinoVoltz 200ah LFP at about $1100 msrp
@80% dod = 160ah net usable
Charger, DC to DC $180 (seems steep, Id shop)
Charger, Wall $85 (one of mine might work)
60ish#
Yeah, its a battery case, some wiring required, not tidy unless you work at it.
But $1365 for maybe 25% more amp hours gross.
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scott100
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# Posted: 12 Feb 2021 03:58pm - Edited by: scott100
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I know LiFePO4 is all the rage these days and will hopefully be mainstream eventually... In your 2nd example on your original post, 160 ah's could be supplied by 4 x Duracell branded GC2 6v golf cart batts available from Sam's club for around $400. These Duracells are made by East Penn (the same company that manufactures the more expensive Deka batteries). These have a good track record for marine use and are quite a bit cheaper than Trojans (but I'm not suggesting that they are the same quality as Trojans).
I've seen all the math showing the long term economy of using LiFePO4, but I'll continue to take the FLA route at least until the price comes down. I'd rather lose a bank of FLA batteries cause I managed to do something wrong with the charging, than kill an expensive LiFePO4 bank any day.
The Bluetti linked to above does not come with the solar panels, so $2k for 166 ah storage, a 2kw inverter, in a nice box with some plugs and an ac charger. It does come in a nice package, though.
I can give you pricing for the system I put at our cabin last year:
6 x 160 watt Renogy panels $1056
8 x Duracell GC2 batteries (470 ah @ 24 v) $839
Victron inverter $324
Victron smart shunt battery monitor $140
3000 watt Aims PS inverter $667
Racks to mount panels on shed roof $267
Misc cables, connectors,fuses, etc $200
So total for a 960 watt system $3493
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gcrank1
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# Posted: 12 Feb 2021 05:04pm - Edited by: gcrank1
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Lucky me (?), I got all the 'system' for free in the purchase but do need new batteries come spring. Im way farther ahead than most here just having to buy new bats.
The GC2s, at say $250 for a pair for 200-225ish gross ah's/100-112ish ah's net (or double all that for a 4 bat-bank) for essentially a three season cabin (call that 40 weeks) and lets say we go once a week, sometimes for several days. Then say each time 'cycles' the battery. That would be 40cycles/yr or 400 in 10years, typically beyond the life of a FLA battery anyway. I could basically abuse them for 4-5yrs and probably get my money's worth out of them.
As has been said before, for part time/wkend use the life cycles of FLA can meet/exceed the need over 10years and at far less investment than LFP.
Aint sexy though.
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scott100
Member
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# Posted: 12 Feb 2021 05:24pm
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True, no sex appeal there.
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Brettny
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# Posted: 12 Feb 2021 08:12pm
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Quoting: gcrank1 The GC2s, at say $250 for a pair for 200-225ish gross ah's/100-112ish ah's net (or double all that for a 4 bat-bank) for essentially a three season cabin (call that 40 weeks) and lets say we go once a week, sometimes for several days. Then say each time 'cycles' the battery. That would be 40cycles/yr or 400 in 10years, typically beyond the life of a FLA battery anyway. I could basically abuse them for 4-5yrs and probably get my money's worth out of them. As has been said before, for part time/wkend use the life cycles of FLA can meet/exceed the need over 10years and at far less investment than LFP. Aint sexy though.
This is exactualy how I also came to the same conclusion of I'm buying GC2s. There life cycle even at 500 cycles (50%dod) would last us something like 13yrs. Then you go add to the fact that your only $200 away from adding 100ah (useable if you feel like you need it a year later.
I have 4 duracell GC2 as a bank right now. I'm going to add 2 more in the spring and possibly 2 more after that if I find I dont get enough sun exposure when the leaf's are out. After 6 batteries my battery box will be maxed out and il just beat the snot out of them and burn some gas if I need to charge them.
Fyi 4 GC2s can run a mini fridge for a weekend along with providing lights and charging cell phones. All ran though a xantrex inverter.
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gcrank1
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# Posted: 12 Feb 2021 10:11pm
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Im encouraged to see my random thinking seems to be in good company 
At this rate I should be able to avoid big mistakes.
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