NBone of the hundred or so LI-Ion batteries I have had have outlasted my car battery.
500 cycles is usially the half life (down to half capacity) or a lot less if exercised heavily.-- Karl Marx said religion is the opium of the people. But Marxism is the crack cocaine.
That's hardly surprising, car batteries spend nearly all their life fully charged and only discharge a little (admittedly at very high current for a short time) when starting the engine. Their chemistry and mechanical design is optimised for this load pattern.
Try comparing them with deep cycle lead/acid batteries with a similar usage pattern, then remember that there are a *lot* of crap Li-Ion batteries on the market so make sure you are comparing similar quality products designed for similar use.
-- Steve O'Hara-Smith | Directable Mirror Arrays C:\>WIN | A better way to focus the sun The computer obeys and wins. | licences available see You lose and Bill collects. | http://www.sohara.org/
I was talking about batteries not solar panels.
Erm try 100kWHr/day system - which assuming shortest days of 6 hours is more like a 17Kw system. If I were going for fully off-grid I'd probably make it a 20Kw peak system.
100 kWHr of storage or about 2000 A/Hr. *IF* you want to be able to run completely off-grid. Which is not what I was suggesting. The only reason I ran through those numbers was to counter the suggestion that you needed enough battery storage to last the whole winter - four or five megawatt hours.See above for the corrected calculation.
More to the point I was suggesting that a system as described in the bit you quoted with a few kilowatts peak power generation and ten to twenty kilowatt hours of storage will reduce grid usage and grid dependency substantially.
Let's take a look - based on 4kW peak generation, 20 kWHr storage and daily use.
In summer with 12-18 hours of daylight it will be a rare day that doesn't see a more energy collected (48-72 kWHr per day peak) than used so there will be almost no energy drawn from the grid and quite a lot dumped, or given or sold to the grid.
In the depths of winter the system will produce less energy per day than is used and something like 3/4 of the energy must come from the grid. But that 20kWHr of storage means that it can all come from off-peak which helps. All in all with such a setup you could expect to use less than 1/8th of the grid energy that you would use without probably more like 1/10th.
In summer or winter with the batteries fully charged a full day of power cut won't cause a problem - the last time I saw a power cut of more than a few hours was more than 20 years ago - that one was three days or so around Christmas which was something of a nightmare.
It then boils down to a simple money question - does 87.5-90% of the electricity bill over the lifetime of the system exceed the cost of the system. Also how much do you value immunity from power cuts, surges, brownouts etc - which of course partly depends on how common they are.
If you can sell that summer energy and buy off-peak in winter the cost savings are even greater than the energy savings - it may even be profitable.
It's the old story - the last 10% of the job takes 90% of the cost/effort. In this case being on the right side of the 90/10 law is pretty good.
-- Steve O'Hara-Smith | Directable Mirror Arrays C:\>WIN | A better way to focus the sun The computer obeys and wins. | licences available see You lose and Bill collects. | http://www.sohara.org/
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