Off grid idea... Thoughts?

[ChrisOlson]

For "first timers", a set of generic deep cycle batteries is a good set of "training wheels" to debug the system and your lifestyle. If you make a mistake, it's a $400 set of batteries you toasted, instead of a set of HUP cells. When it's all dialed in, then the top of the line cells make better cent$.

That's true, but there's another way to look at that too. Those generic marine/RV "deep cycle" batteries are really a hybrid type. They are not true deep cycle. They are designed for casual use in boats and RV's, they are cheaply built and have a high premature failure rate. Buying a set of four of them for an off-grid system almost guarantees at least one will fail in the first year even if you do everything right.

At the bare minimum at least buy four Trojan T-105's for "training batteries" instead of four of those 12V ones. The manufacturing on those 12V ones is so poor that I have never seen a pair of them that are matched good enough to be used either in series or parallel. In series on a 24V system one will charge at 15.0V and the other at 14.6V, and in parallel on a 12V system the stronger one will do all the work while the other one watches. With T-105's you can at least have a couple strings that will match better because they are higher quality.

[Sunking]

Well guys maybe I am the odd man out here but for traing I would only be using one battery on a proof of concept small scale. 4 T-105s is roughly $550. That is an expensive boat anchor.

[ChrisOlson]

Well guys maybe I am the odd man out here but for traing I would only be using one battery on a proof of concept small scale. 4 T-105s is roughly $550. That is an expensive boat anchor.

Well, this is true too. Except for one correction. A set of wrecked T-105's is good for ballast. The shape ain't quite like a Danforth so I don't know how well they'd work as an anchor.

[Joeybags]

I've seen plenty of 12V systems in off-grid cabins, sailboats (up to 36-37 footers) and RV's. And it does work fine but you can't power large loads with a 12V system (at least not economically). I consider 12V to be OK as long as your peak load isn't much over 100 amps on the battery bank. Higher than that you should be looking at going to 24 or 48V.

For us off-gridders the most expensive thing we got (and have to periodically replace) is batteries. If you have utility power I don't really recommend playing around with an off-grid system because the batteries cost too much. We need them for off-grid power because without them we're kind of screwed. But if you can get utility power for 20 cents/kWh you pay less than JUST what our batteries cost us over the long term for every kWh we use. If you have a legitimate use for the batteries, like in a RV or sailing yacht or something, then fine. But I have seen countless "off-grid" systems that people have as a hobby thing in a utility connected home that get abandoned when the batteries go to hell.

And those little 110ah 12V batteries won't last much beyond one year being cycled every day. A real 5 kWh off-grid battery bank that can survive daily cycling for many years is going to cost you about $1,200. The reason us off-gridders don't buy them little off-the-shelf 110ah 12V batteries is because they are too expensive. They cost about double per kWh of lifetime storage that good ones cost.

Don't throw your money away.

If you do intend to put in a 12V off-grid system no matter what, you can get like Trojans at the low end for about $400 each for L-16 6V for $800 total cost. At the high end you can get the big 12V Rolls 12CS - this battery has about 400ah capacity at the 20hr rate and it is not too bad for weight - they are around 300 lbs full of electrolyte. The big Rolls also has individually replaceable cells in the event one would go tits up after a few years. The Rolls is around $1,200.

http://www.dcbattery.com/rollssurrette_12cs11ps.html

For cost/kWh, the little "marine" deep cycles (which are not real deep cycle batteries) will cost you the most because you'll go thru several sets of them in short order. They lose capacity very fast and will be down to only about 75% of their rated capacity after 50-60 cycles.

The Trojans will be in the middle and give you 5-7 years depending on cycle depth.

The big Rolls will cost you the least and give you 10+ years of service at 50% DoD cycling, and in that amount of time you're almost guaranteed to have to replace a cell or two to get 15 years of life from the battery. The cells are $212 (today's cost) plus shipping from Rolls Battery in Springhill, Nova Scotia.

That's the best reply so far!! Holy crap!

I wanted to do only one circuit as a test.. Maybe 15 amps on the AC side..

Anyway, I need to switch gears for a second.. I just found Yingli panels for a great deal.. Open voltage is 37v are these any good?