http://calsolarsolutions.com/rvandcabin.html

To summarise, you should know the following :

• Voltage is variable, it is like water pressure, devices can handle changes in voltage as long as it isn’t too much or to little.
• Amps are also variable, it is like the speed of the water flowing through a pipe.
• AmpHours is a rating of how long you can maintain that speed, it’s the bucket of water that will eventually get empty.
• Watts is the overall ‘usage’, Watts = Volts x Amps

Batteries

• Batteries are a 12V DC system, but they are really closer to 13V
• You need more than 17v or more to get a good charge into a battery
• Batteries do not like to be discharged below 12V, or 50% of their capacity
• A 50AH battery can give 1A for 50 hours, or 2A for 25 hours

Panels

• Panels are rated for their perfect conditions (midday, full sun, 25 deg C)
• Heat (aka the playa) reduces a panels’ output
• The angle to the sun reduces a panel’s output
• An 18V,75W panel really only puts out 15V,60A on average

Charge controllers

• 3-stage or PWM controllers are better
• controllers stop overcharging the battery
• controllers have a load (Amps) rating, if you panel has too many Amps, it will blow out the controller

John Wiles NEC Code Corner articles http://tinyurl.com/57uqfj

PHOTOVOLTAIC POWER SYSTEMS and the NATIONAL ELECTRICAL CODE: http://tinyurl.com/59thse

http://quantumgravitics.tripod.com/id9.html

So you have paid big bucks for your 30 batteries to run your house for a week, but after a month, they have all died. What went wrong?

Of course YOU DON’T WANT A CAR BATTERY!

A car battery is designed for short bursts of high output, for starting a car mostly.

You want a deep-cycle battery. They’re still 12V, but different sizes have different capacities. The Capacities are in Amp-Hours or AH. The higher the AH, the bigger the capacity (and the more expensive). If you go the roll-your-own route, take the advice here and buy a cheap costco deep-cycle, as you’ll probably kill it pretty quick.

Typically, for people who have large requirements, they get multiple batteries and wire them together.

Math Fun: Watts = Volts x Amps the “typical” 12V battery is rated at about 100 amps. You can safely use half of it, without damaging the battery. So a typical costco deep cycle battery holds 12v x 50a= 600 usable watts

How to wire for balanced voltage distribution (2 examples):

Why to “Diagonal Wire”: http://www.smartgauge.co.uk/batt_con.html

Several Different types

* Flooded (original style, open caps, add water)

* Gel

* AGM

* Spiral

* Starting

* Deep Cycle (Difference between Starting & Deep Cycle batteries)

All need to be recharged soon after being depleted, and none like more than a 60% discharge, the deeper the discharge, the more internal damage, and shorter the overall lifetime. Sitting discharged, sulfur crystals start to form, and they obscure the lead plates, reduceing capacity. (sulfation)

Hobbyist site (Bill Dardens Battery FAQ) http://www.uuhome.de/william.darden/

Commercial site explanation, but they are not the only answer http://www.battery-care.com/

]]> http://ae-zone.org/2009/09/lead-acid-batteries/feed/ 0 http://ae-zone.org/2009/09/evs-electric-vehicles/ http://ae-zone.org/2009/09/evs-electric-vehicles/#comments Tue, 15 Sep 2009 04:41:47 +0000 Transfered from previous site. http://ae-zone.org/?p=102 EV’s are electric vehicles.

Some info about Plug-In Hybrids

http://www.eaa-phev.org/wiki/Plug-In_Hybrids.

“Can I charge my electric scooter by mounting a solar panel on the handlebars?”

A small solar panel in the 5-watt range looks great mounted to a scooter. Unfortunately, the capacity of such a panel is inadequate to support practical daily use.

“What size panel would be needed for a practial scooter solution?”

About 85-watts to 200-watts seems to work well during the Burning Man art festival. Panels of this size are too large for scooter handlebars, however, and would be best placed over a larger vehicle as a shade or pulled behind a scooter on a lightweight trailer.

Although the guideline above will work, it may lead you to obtain a more expensive panel than you need, or it may lead you to run down your scooter’s battery. It all depends on the size of the scooter (and you) and the amount of time that you plan on using it each day.

A more accurate determination requires you know the power usage of your moving scooter. If you or an electrically minded friend (an engineer–they’re good for something, you know) can measure the scooter’s current consumption in amps during operation, then multiply that number by the scooter battery’s nominal voltage in volts (usually 12 or 24). The product that you get is the scooter’s power usage in watts. Expect a quantity of a few hundred watts. Compare this value to the solar panel’s power capacity, which also is in watts. If they’re about the same, you can spend about half of the time running and half of the time charging. If the panel’s rating is smaller than the scooter’s power usage, then you’ll need to spend more time charging than moving.

The estimate above is another guideline, however, because it ignores the angle to the sun, dust, whether your scooter can charge and run at the same time, and other such details. The purpose of this estimate is to teach you that 5 watts ain’t enough, and 500 watts probably is a bit more than necessary.

• Q. I need to run wire a long distance from the modules to the inverter. What size wire do I need?

• A1. Follow the link to this calculator: http://www.electrician2.com/vd_calculator.htm

• A2. Or this downloadable spreadsheet: http://www.uwgb.edu/nevermab/voltage_drop_calculator_.xls

Understanding the hazards

associated with voltage and knowing the principles of safety and the importance of certification are the keys to safe design and product use. Even low voltage is hazardous and can damage products and harm users.

http://www.edn.com/article/CA6330100.html

This article is aimed at the electronics industry, but is in mostly plain english.

Strongly suggested for AEZ members

NEC code interpetions for AE systems http://www.sandia.gov/pv/docs/John_Wiles_Code_Corner.htm

HV arc info http://205.243.100.155/frames/longarc.htm http://www.teslamania.com/

When working with over 42 Volts, keeping one hand in your pocket will help prevent a fatal current flow thru your heart, thereby possibly saving your life.

• A 60% chance of mortality exists for a hand-to-hand current pathway through the heart, and 20% mortality exists for a hand-to-foot path. An old adage says to place one hand in your pocket when working near hazardous electricity so that current does not pass through your chest. A better recommendation is not to touch hazardous voltages!

Contains no Hero Engines, Ammonia, or Razor Blades.

Let me use an arbitrary example from my own camp. I have a 20-watt panel to charge a small lawnmower battery (i.e. even cheaper than a car battery – and actually two of them). I plan to run an MP3 player rig all the time that draws 0.2 amps from a cigarette lighter plug (12 volts) and I have a string of LED lights that go through an inverter and are only on at night with a night-day switch – they draw 2 watts or so.

So my MP3 player uses 0.2 amps * 12 volts = 2.4 watts; * 24 hours = 57.6 watt-hours per day. The LED lights are on for about 10 hours or so, so that’s 2 watts * 10 hours = 20 watt-hours. In total, I’m talking about needing 77.6 watt-hours per day – which I’ll just round up to 80 watt-hours.

Now, given 4 usable hours of light in a day, 80 watt-hours / 4 hours = 20 watts. (I swear I didn’t do this before.) That’s the minimum size of my solar panel rig. For the battery, 80 watt-hours * 2 = 160 watt-hours; / 12 volts is about 13 amp-hours.

Thus, what I should have is 20 watts of solar panels and a 13 amp-hour battery. The lawnmower batteries have a capacity of about 15 amp-hours each for a total between the both of them of 30 amp-hours. Technically, this is what’s called “too much”, but it’s okay I guess because the lawnmower batteries are not deep-cycle batteries and shouldn’t be drained like deep-cycle ones. Plus, to charge them, you should be right around the “0.1C rate” – that is, the capacity in amp-hours * (0.1 amps/amp-hour) – so I should be charging them with about 3 amps. The 20-watt panel can only deliver about 20 watts / 12 volts = 1.7 amps so it’s not going to properly charge them. However, it’s not _that far off_ so it’ll still work. Trying to charge a 300 amp-hour battery just wouldn’t work with a 20-watt panel: the 0.1C rate would need to be 30 amps, and the 1.7 amps from the panel will barely overcome the battery’s self-discharge.

]]> http://ae-zone.org/2009/09/sample-calculation-of-one-camps-power-requirements/feed/ 0 http://ae-zone.org/2009/09/ohms-law-or-how-i-learned-to-love-electricity/ http://ae-zone.org/2009/09/ohms-law-or-how-i-learned-to-love-electricity/#comments Tue, 15 Sep 2009 04:27:51 +0000 Transfered from previous site. http://ae-zone.org/?p=83 DISCLAIMER – I am not an electrician, I are an engineer of the rocket scientist variety. (but I am still alive) I may mis-quote something here, or someone else may make a poor edit. Mistakes can kill or injure you, it’s your choice to listen to (or not) any advice you find on the internet. Mike

Some basic abbreviations

Electromotive Force = Volts = V or rarely, E

Current = Amps = I

Resistance = Ohms = R

A common analogy is Volts is like water pressure, low or high.

Amps – like a small tube, or a firehose, a little flow or a LOT

Ohms – a restriction in the water line, or a kink in the hose, slows the flow down

Power = a measure of work energy = Watts = W or P (Also handy to convert from different voltage scales – 100W at 5V (20 amps) is the same as 100W at 120V (0.833A))

Formulas (secret electrical incantations):

The power triangle (power formula) The magic triangle can be used to calculate all formulas of the “electric power law”. You hide with a finger the value to be calculated. The other two values show then how to do the calculation.

Shortcut – the Ohms Law Triangle V over I * R

This simple formula describes the relationship between voltage, current and resistance:

Voltage = Current X Resistance or V = IR

Current = Voltage / Resistance or I = V / R

Resistance = Voltage / Current or R = V / I

Ohms law can easily be remembered using the triangle below. Cover Up the value you want to find, and treat letters next to each other as multiplications, and letters above each other as divisions. Try it!

Formula Wheel (uh oh – no more secrets now ! ) http://www.sengpielaudio.com/calculator-ohm.htm

All of the above is valid only for DC circuits and AC circuits that contain only resistive loads, like incandescent lights and simple heaters. AC circuits with reactive loads like motors, transformers, florescent lights, require one to consider the phase angle offset between voltage and current which makes the math more complex.

And when working with over 30 Volts, keeping one hand in your pocket will help prevent a fatal current flow thru your heart, thereby possibly saving your life.

Working with batteries or heavy currents, remove metal jewelry – if it shorts and arc welds itself to something, it will get very hot, with your little finger trapped inside!

And, least I forget – House Wires, are commonly Black, White and green. Always remember the Black Death. That is the color for the HOT wire – Black, if the place was wired right. It should always be connected to the toughest thing to touch, the shorter of the 2 slots in an outlet, or the deep center contact of a lightbulb.

Building wiring may also involve wires of many other colors, all of which are likely to be hot at least part of the time. Also it is entirely possible (and legal) for white or green wires to be hot. The best rule is to assume all wires are hot until you prove otherwise by testing.

There is a simple wattage calculator here
http://shop.altenergystore.com/Calculators/OffGridCalculator.html
that can help you determine size of panels you may need.

You can buy simple voltage testers here:
http://www.thinkgeek.com/stuff/41/lebedev.shtml

Back to the Electrical Faqs page.

Back to the AEZ Wiki Start page.