Longtime lurker going offgrid

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Re: Longtime lurker going offgrid

Postby offgridCBR » Tue Feb 09, 2016 3:52 pm

Thanks again everyone for the recommendations!

I am in contact with A&A Worm Farms and they are similarly priced to the aerated systems which isn't bad. Thanks Cherokee for adding some peace of mind about usage, we have never used much power and I feel that the 13.4kWh at 70% DoD should be sufficient >95% of the time.

Thanks for the generator advice, I was definitely leaning to something small/readily available and for charging the batteries directly. What are the considerations when choosing between diesel/petrol/lpg?

There is plenty of firewood around, so will look into integrating some form of additional cooking. My family have one of those wheat heaters but it seems to only heat one room of the old farm house...

Hail is definitely a concern where we will be located. All the paperwork is going through now so getting closer to finalising house etc. Is it preferable to put the battery/inverters in a little insulated room joined to the south side of the house or have some form of internal room?

Thanks tom regarding the BMS info, this is an area where I don't really know what is going on...
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Re: Longtime lurker going offgrid

Postby Gordon-Loomberah » Tue Feb 09, 2016 4:33 pm

With care and a bit of load shifting it will be ok >99% of the time for a low energy use household, with no to minimal need for generator use. As I've mentioned previously, I ran for over 2 years with zero generator use after installing my LiFePO4 battery, with significantly higher energy use than you have.

I've used all 3 fuel types in a generator over the years, and wouldn't bother with a petrol generator again, and I find LPG to produce the least offensive fumes, and more convenient for refuelling. With diesel you have the possibility of running on biodiesel/vegetable oil, so it is potentially the most environmentally sound. I have a diesel motor here that I'd like to run renewably on biodiesel when I can find some locally, to drive a large alternator for battery charging.

My preference is for battery and inverters etc to be not inside the house, in case there is some sort of fire or other catastrophy- unlikely, but you cant rule it out 100%!

Being careful and with a bit of knowledge, BMSs are not absolutely necessary, but definitely a very good idea if you are new to operating an off-grid system and unfamiliar with Lithium battery behaviour, so I'd recommend you utilise one.
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Re: Longtime lurker going offgrid

Postby Privatteer » Sat Feb 13, 2016 3:20 pm

Just a thought but if you get snow as mentioned it might be worth installing the panels on a greater angle than usual. Slightly less production summer, more in winter but the main advantage is any buildup is more likely to slide off.

Easy to do if you are going with a ground mount arrray, but roof mount is not that hard to do either.
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Re: Longtime lurker going offgrid

Postby karrak » Sat Feb 13, 2016 11:14 pm

We have been living off-grid full time for around three years now.

Like you our power usage is fairly modest at around 3kWh/day in winter and 5-6kWh/day in summer. The reason for the difference being that we use an electric oven in summer when we have excess power and an Esse Ironheart wood stove/heater for cooking and heating in winter. This stove is not cheap but is incredibly efficient and the oven works very well. We have a couple of the cheap portable induction cooktops that we use all year, only problem with them is they generate allot of EMI(electromagnetic radio interference). We never find we need to use them at more than half power which is around 1kW.

For water heating we have a vacuum tube water heater which only cost $1,500 about six years ago from Run On Sun. This unit has no form of booster and gives us enough hot water even in winter although there are a few days now and again where the water is not hot enough for a shower. It might be worth looking at something like this with an electric booster and big storage tank and a few extra solar panels and a smart load sharing system that would share the solar power between charging the battery and the heating the water in the tank.

I agree with Gordon regarding the small generator, you only need it to be big enough to give enough power to supply your average power consumption and provide a little extra to slowly charge your battery. 5kWh/day is only 208W continuous.

Simon
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Re: Longtime lurker going offgrid

Postby offgridCBR » Mon May 23, 2016 2:57 pm

It's been a while but finally beginning the approvals process with council and was wondering where to purchase the LiFePO4 batteries from? Feel free to PM me with options but the only place stocking the Winston batteries appears to be the old yellow version.....

Thanks again for all the pieces of advice. Recently chatted to a few locals who are offgrid are they are still going with lead acid surprisingly.
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Re: Longtime lurker going offgrid

Postby jules » Mon May 23, 2016 3:28 pm

Recently chatted to a few locals who are offgrid are they are still going with lead acid surprisingly.


Maybe, maybe not. I'd suggest it depends on the long term relative lifespans of LiFePO4 as against Lead-acid batteries, particularly since it's possible to get 20+ years out of the latter.

It would be interesting to know what's being used for back up supplies by people like Telstra these days, though admittedly they're using the batteries in a different way to households with solar power.
Primary system: .8KW Trina panels; Plasmatronics PL40; 1,000Ah VRLA 12X2V battery bank; 1.7KW Selectronic inverter

Veteran system, semi retired: 6 X 55W Solarex 12V panels; Fangpusun CC; 6 X 2V, 35 year old 550Ah lead acid flooded cell batteries.
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Re: Longtime lurker going offgrid

Postby Gordon-Loomberah » Mon May 23, 2016 3:38 pm

I think for emergency backup purposes Lead-acid may be better suited to the job than Lithium, which is better for off-grid cycling use. I use AGM Lead-acids for my aquaponics backup power supplies, since sitting fully or near-fully charged all the time isn't ideal for Lithium, but is fine for Pb-acid. Some Lead-acid batteries, such as I have on one back-up water pump, can be run flat quite a few times before they are stuffed, but Lithium chemistry is much less tolerant of such treatment.
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Re: Longtime lurker going offgrid

Postby offgridQLD » Mon May 23, 2016 4:49 pm

I think lithium fits in better with a (generator free) offgrid system due to not having to worry about cells sitting at less than 100% SOC.

The other big thing you will notice is just how well they take a charge. It's not often your PV array will be to big with a lithium bank. Given that big arrays are becoming the norm due to $ pr watt of PV.

You can hammer them with heavy loads to.


I hear lots of talk about 20 year old lead acids have never seen 20 year old lead acids performing well. I do have some 8+ year old small lithium cells that are working well.

It all boils down to $ over the life of the bank that will do what you demand of it.

I'm enjoying my lithium's. The fact that they are more expensive pr kwh is doesn't equate to lead being better. Just like any mature product that has reached it's manufacturing peak. It's cheap but if lithium was the same cost you wouldn't buy lead acid.

If I had to do it all over again I wouldn't go LIfepo4 as the few options in Australia are just to price now days. I would go 2nd hand OEM EV salvaged cells at a fraction of the cost and great Japanese quality.

Yet I can understand people wanting a turn key solution.
Offgrid 2008, Selectronic PS1 6kw/48v inverter, x 2 Midnite solar classic 150 MPPT, 3960w NE PV 24 x 165w BP panels, 4200w NW PV 21 x 200w DAQO PV, 16x400ah lithium.
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Re: Longtime lurker going offgrid

Postby offgridCBR » Mon May 23, 2016 5:11 pm

What would the expected life span be of the 2nd hand batteries?

The bloke I was going to get to install the batteries was talking about an LG option coming out soon with 10kwh base plus 5 kwh expansion packs. (This is at 90% dod).
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Re: Longtime lurker going offgrid

Postby offgridQLD » Mon May 23, 2016 5:39 pm

You want 15 - 20Kwh For the typical house.

Don't know the lifespan But they would be near new so perhaps within 5% to 10% of what the new cell life would have been And as long as any other high spec Jap lithium cell from a big brand name would last.

I tend to only trust my own experience with lifespan on cells. Given I have some 8+ year old lifepo4 cells. I bank on 10 years minimum from lifepo4 cells well managed. I hope to get that from my Lifepo4 house bank.

I payed just over $500 each for the cells 16 of them $8000 for the raw cells (the other lithium based accessory gear purchased 1st up you can use again on the replacement cells) . So budgeting $800 a year for replacements. If I need it at the end of the 10 years then ok if not all the better cost pr year drops even more.

I wouldn't recommend used (near new) EV cells to just anyone. Only some that is a keen DIY person who understood the cells well and had confidence and experience with them to go down that path.

I just see it as a great way to recycle as people are always damaging cars + the cost benefit in the salvaged cell price.

I friend purchased an entire EV (imiev) with 16kwh battery bank. Car had a smashed LED headlight ($2500 to replace headlight!) and a broken plastic bumper. He payed just over $2000 for the entire car! He ended up getting two more for a similar price at action. One his wife wouldn't let him pull apart and she now drives around the other two are in parts (lucky me got the battery box from one) Nissan leaf cells are readily available to as raw cells or in complete wrecked cars.

The LG cells would most likely be of good quality and have some reputable warranty if your having them suplyed and installed. What price are they?

Kurt
Offgrid 2008, Selectronic PS1 6kw/48v inverter, x 2 Midnite solar classic 150 MPPT, 3960w NE PV 24 x 165w BP panels, 4200w NW PV 21 x 200w DAQO PV, 16x400ah lithium.
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