Off grid folks up here use a variety of batteries, all depending on budget. RV/Marine batteries are also not that great -- maybe a year's life in a offgrid home. Going from cheapest to most expensive (and shorter life to longer life), these are the most common:
6v golf cart batteries
Glass matt 6v gel cells
L-16 size 6v deep cycle batteries
2v Forklift batteries (these ROCK! Absolutely the best choice, but very expensive).
DAN
Car batteries are made to put out lots of amperage for a short time, then get recharged immediately. For running an off-grid home, you need batteries that can survive being deep-cycled. Car batteries usually last under a year when used to power an off-grid home. And, you won't find many regular incandescant lights in off-grid homes, either -- we use all fluorescents and compact fluorescents to save power. DANF
I know of only a couple off-grid people who use 120v battery banks, but it indeed would have many advantages. Most people are moving away from 12v systems entirely--That 17 foot turbine wouldn't be practical at 12v -- way too much resistance loss in the stator and the wiring to the house.
The issue is cost -- batteries for off grid come in 6v or 2v, never 12v. So a dozen (or 36) more at $200 a pop would be cost prohibitive. And, there are no readily available inverters to convert this to AC. There are industrial inverters, but they are very expensive and lack the features off-grid dwellers expect from an inverter.
The folks that DO use 120vdc systems usually scored a great deal on a truckload of surplus batteries! And 120vdc is common in industrial backup systems -- radio relay towers, etc. My battery bank of 12 2v batteries was split up from a 120vdc system like that. My 12 batteries weigh a ton -- literally!
DANF
"Air Gap" actually refers to the distance between the attracting pairs of magnets. The 3/32" referred to in our page is the physical clearance between the spinning magnets and the cast stator.....the smaller the better, and bad news if it rubs.
So basically we are eliminating the need for tight tolerances and ferrous cores (hard to build in a home shop) by throwing lots of magnets at the problem! It works. DANF
We've made machines both with laminates and with ferrous cores, and low windspeed (much more common than high winds, and the most important part of the power curve) performance suffers. So the large air gap and large amount of magnetic material is a compromise to help low wind power output.
There's very little power available in low winds (see my recent article in the Energy Self Sufficiency Newsletter for more details), so it's critical to extract all the power possible from it.
Fortunately NdFeB magnets have dropped so much in price since the early 1980s when they were invented, that compromise is now cost-effective....not many years ago, it would've been prohibitive. Hugh Piggott's pioneering Brake Drum Windmill used big ferrite magnet blocks, and required a very small airgap and salvaged transformer cores to make good power. Hugh has also switched to a large-airgap design with big NdFeB magnets, and no longer builds or gives classes in making that older design.
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Off grid folks up here use a variety of batteries, all depending on budget. RV/Marine batteries are also not that great -- maybe a year's life in a offgrid home. Going from cheapest to most expensive (and shorter life to longer life), these are the most common: 6v golf cart batteries Glass matt 6v gel cells L-16 size 6v deep cycle batteries 2v Forklift batteries (these ROCK! Absolutely the best choice, but very expensive). DAN
Car batteries are made to put out lots of amperage for a short time, then get recharged immediately. For running an off-grid home, you need batteries that can survive being deep-cycled. Car batteries usually last under a year when used to power an off-grid home. And, you won't find many regular incandescant lights in off-grid homes, either -- we use all fluorescents and compact fluorescents to save power. DANF
The issue is cost -- batteries for off grid come in 6v or 2v, never 12v. So a dozen (or 36) more at $200 a pop would be cost prohibitive. And, there are no readily available inverters to convert this to AC. There are industrial inverters, but they are very expensive and lack the features off-grid dwellers expect from an inverter.
The folks that DO use 120vdc systems usually scored a great deal on a truckload of surplus batteries! And 120vdc is common in industrial backup systems -- radio relay towers, etc. My battery bank of 12 2v batteries was split up from a 120vdc system like that. My 12 batteries weigh a ton -- literally! DANF
So basically we are eliminating the need for tight tolerances and ferrous cores (hard to build in a home shop) by throwing lots of magnets at the problem! It works. DANF
There's very little power available in low winds (see my recent article in the Energy Self Sufficiency Newsletter for more details), so it's critical to extract all the power possible from it.
Fortunately NdFeB magnets have dropped so much in price since the early 1980s when they were invented, that compromise is now cost-effective....not many years ago, it would've been prohibitive. Hugh Piggott's pioneering Brake Drum Windmill used big ferrite magnet blocks, and required a very small airgap and salvaged transformer cores to make good power. Hugh has also switched to a large-airgap design with big NdFeB magnets, and no longer builds or gives classes in making that older design.
DANF Otherpower.com IT director http://www.otherpower.com/contact_op.html
PS and, yeah, we are in the magnet business too! ;~)