Battery-power explained

Discussion in 'Energy & Electricity' started by NaeKid, Dec 24, 2010.

  1. NaeKid

    NaeKid YourAdministrator, eh?

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    I have been looking at / researching what I can about batteries, solar-systems, wind-generators, wiring, etc for quite a few years now. I have been using a calculator to try to figure out what works in theory vs. what works in reality.

    This morning I found a quote that explains very well what I have learned over the years:

    For a solar-panel to "push" power into a battery, it must be able to do so faster than what the draw out of the battery is. My 80-watt solar panel on my camper pushes (calculated) 5-amp of power into the batteries at high-noon. For me to replace my 80-watt panel with a 120-watt panel, I would only gain approx. 3-amp of power (about 8-amp calculated). To put on a pair of 120-watt panels would give me about 16-amp (calculated) worth of power into the batteries.

    Now, if I run all the lights / pump / furnace in the camper at the same time, the power-draw exceeds the maximum amount of power that the panel can provide, so, the power must come from the batteries, draining the power from them (think of the battery as a water-reservoir). If the solar-panel doesn't have enough time to refill the battery before the end of day, the amount of available power leaving me with less than a full "reservoir" of available power.

    For a short night in the summer where the power-draw is low, I should have more than enough power in the batteries with my current setup. For a long night in the winter (and a very short charging day-time) the power-draw could bring the batteries down to "dead" state where there isn't enough available voltage to run the camper.

    To compensate for that, I could add even more batteries to the mix for more "reservoir" available but I would still need to add more solar-panels to make sure that there is sufficient "flow" into the batteries. It is a never ending cycle of adding more till you reach a point of "more than enough" - and at that point you can stop spending money on wiring, panels and batteries and start living again.

    How do you decide when it is enough?

    Trial - trial - trial. Live it and you will figure out fairly quickly what is enough. But, sometimes that answer isn't good enough. Sometimes hard-numbers are needed and an electrical-engineer might need to be hired to really work your system over to locate areas of phantom power draws. If you cannot afford to hire one, see about talking to some teachers / students at the local college to see if they could help you out with the math as part of a "practicle" portion of the class.



    Closing-thoughts

    We have members here who are living off of solar-panels and batteries and they have shared their experience with all of us. If you are seriously considering making your own power, search the forum and answers will slowly appear.


    Good LUCK!!
     
  2. nj_m715

    nj_m715 www.veggear.blogspot.com

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    The best way to save when using solar is to cut usage as much as you can. Running energy star appliances, using cf or led bulbs and stop phantom loads etc. A kill-a-watt will tell you how much any item is using. Needing less solar is the cheapest way to use solar, if I'm explaining myself well enough.
     

  3. mosquitomountainman

    mosquitomountainman I invented the internet. :rofl:

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    Very, very good point!!!! The biggest mistake we see is people trying to live off-grid the same way as they did on the grid. It won't work unless you have lots of money to invest. It's much more economical to cut your needs than to expand your soalr power system.
     
  4. mosquitomountainman

    mosquitomountainman I invented the internet. :rofl:

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    Generally, if by sundown your batteries are not fully charged you need to add more generating capacity (more or larger solar larger panels) or reduce daytime usage.

    If by morning your batteries are drawn down to the minimum you need to add more batteries or reduce your night-time usage.

    Use power strips everywhere and shut them off when you aren't using the appliance hooked to them. Televisions, computers, microwave ovens and many other appliances have circuitry that draws power even when the appliance is turned off.

    Learn to use less power on overcast days.

    There's an article on the web that's somewhat dated now but has some good information for those contemplating an off-grid life. The title is "paring down for off-grid living." Run a search and it should turn up. I believe it was first published in Backwoods Home magazine.
     
  5. Sonnyjim

    Sonnyjim Prepping

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    Paring down for off-grid living by Steven Gregersen Issue #93

    Just read it, great article.
     
  6. The_Blob

    The_Blob performing monkey

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    and once you're dialed in... add 30% ;)

    once thing many first time solar panel owners forget... keep them accessible enough to keep clean easily! IMO that means only put them on the roof if you have to :p
     
  7. NaeKid

    NaeKid YourAdministrator, eh?

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    That guy sounds like he knows what he's doing ... would love to meet him and chat with him in person some day! :beercheer:

    The best reason to put panels on the roof is so that they are relatively protected from certain elements that can do them harm, but, they become a "fixed" asset and it is difficult to adjust them due to the angle of the sun through-out the year. A combination of fixed panels and adjustable panels might just be the better choice to go with.

    IE: If you are running independant power circuits for charging batteries that are dedicated to certain sections of the home, you could use smaller fixed-mounted panels to keep those batteries topped-up. Main living areas such as living-room / kitchen are primary zones of the house, so you would want the best panels / batteries dedicated there. For other zones of the house where you visit for short amounts of time (like a bedroom or bathroom) a small battery and small panel could keep that area safely powered all year long.
     
  8. Tirediron

    Tirediron RockyMountainCanadian

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    The other thing to remember is that Lead acid batteries involve the transfer of material every charge/discharge cycle and have a life span, factor this in when planning a system , also bear in mind that one bad battery can wreck the others.
     
  9. labotomi

    labotomi Well-Known Member

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    Sorry to nitpick...If this works for you then great, but it is flawed in it's explanation and actually it's logic.

    Increasing the resistance in a circuit does not increase the voltage, so increasing the resistance will decrease the flow and therefore reduce power.

    A 40W light bulb has more resistance than a 100W light bulb (and 100W is definitely more than 40W)

    Power in a simple DC circuit is equal to (current squared*resistance)
    if resistance is doubled the current is halved and since it's effect is squared it has more of an effect therefore actual power is reduced.
     
  10. labotomi

    labotomi Well-Known Member

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    This is true, but a properly maintained battery can last for quite a long time. We had a very large battery on submarines. 128 cells, each over 1100 lbs dry with a 11000 amp hour capacity (3 hour rate). I was involved in one battery change out and it was just due to scheduling not because of any problems. The battery was over 15 years old and not a single cell had gone bad in that time. We charged it weekly and discharged it very slowly the rest of the time (trickle discharge). Once a month we discharged it rapidly and then performed an equalizing (conditioning) charge.

    If you don't abuse the battery it will last a long time. If it's neglected (over discharged, overcharged, never conditioned, too hot/cold, electrolyte levels not maintained or improper acid concentrations) it will fail prematurely. The electrolyte concentration shouldn't change if the level is maintained. Just remember that any charge or discharge causes hydrolysis turning the water into hydrogen and oxygen. this causes the level to go down so you routinely should monitor the level and add water to maintain level and thus acid concentration.
     
  11. The_Blob

    The_Blob performing monkey

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    a good Ohm's Law chart

    [​IMG]

    you should be able to do any DC calculations you need with it

    AC only takes a little more math, but not much ;)

    Ohm's Law for AC

    is a simple calculator
     
  12. labotomi

    labotomi Well-Known Member

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    LOL...It may seem simple to you now, but it looks intimidating to those who haven't studied the subject. How many here would have an idea of what CosΘ represents or even that voltage and current aren't necessarily in phase with each other?
     
  13. The_Blob

    The_Blob performing monkey

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    luckily, I've always been an 'engineering nerd'... ever since I found a Radio Shack 200-in-1 electronics hobby set at the flea market for $1, I was hooked
     
  14. labotomi

    labotomi Well-Known Member

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  15. dawnwinds58

    dawnwinds58 The Kentucky Lairkeeper

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    Could you please relate the patterns of "trickle discharge, and conditioning" as it applies to the use of deep-cycle batteries in an energy array?

    We're aimed more at wind being the primary source and solar for selective potions of the load here.

    Let some dummy set off a bomb or one volcano have a "hissy fit" and sunlight is reduced which in turn reduces your ability to produce enough energy, and reduces daylight for plant growth. I figured on having a backup plan. No matter how hot, or cold, or dark, there is always wind being produced somewhere due to temperature fluctuation and base topography. We're in a wind funnel here between lakes and rivers which gives a higher than average wind speed for this area.
     
  16. CulexPipiens

    CulexPipiens Still waiting for the zombies.

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    Take a look at

    DIY Solar Panel help - tutorials, calculators and design tools for solar power

    and specifically the "Solar Simulator" and "Design Tools" buttons near the top.

    I'm following these solar discussions with great interest as I'd like to setup a system that will supply power for 3 days with no sun for the following:

    a refrigerator (24 hours/day),
    a couple of lamps (3 hours each/per day, CF or LED bulbs)
    15 minutes (per day) of some other high capacity load (microwave, for example)

    So enough batteries to supply all of above (for 3 days), plus solar panels to refill the battery bank in one day winter or summer. Eventually I'd like to add a small scale wind turbine as supplemental power when the sun isn't shining.

    Ideally it would also be grid tied but with a cut off switch to keep it running isolated from the grid if/when it goes down.

    Those are my goals, but this is still very preliminary as I know very little and am trying to learn enough to be able to spec out a system at which point I can first see if/when I'll be able to afford it.
     
  17. NaeKid

    NaeKid YourAdministrator, eh?

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    Culex - if what you are hoping for is a grid-tie system, you might want to look at something like a UPS ( Uninterruptible power supply - Wikipedia, the free encyclopedia ) to provide your power for you. There are some units available on eBay right now (search-term: 5000 inverter will find it or look for member dcacpower) that will pass-through 120-volt and will charge batteries attached to the unit. When the power goes out, it will automatically switch-over to the battery-power and continue to provide 120-volt AC to anything downstream. You don't need to worry about back-feeding the grid with this as it is directional-power (only feeds power to stuff attached to the unit).

    You can also attach solar-panels and/or wind-generator to the system to keep the batteries alive in case the power goes out for long-term (anything greater than a week).

    You can see a picture of the 5000 watt (10,000 watt peak) unit below and there are also 2500 watt (5000 watt peak) units available as well. The best prices I have found are around $600 for the "inverter" (which is more of a UPS-based controller) in 5000-watt draw and only slighly cheaper for the 2500-watt units ...



    As as aside: there are some inverters designed for OTG as well that do not have the 120-vac system to charge the batteries and they are significantly cheaper than the ones that have the built-in battery charger.
     

    Attached Files:

  18. dawnwinds58

    dawnwinds58 The Kentucky Lairkeeper

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    I've done alot of "surf, save, and study" looking for wind power ideas. And as I my husband says, I never leave it alone but modify and customize everything. I spent mu whole life in a world that didn't "fit" me, so I'm used to changing things to fit my needs. These 3 links are the plan right now, unless we come up with a better modification.

    Link 1- information on building a vertical axis turbine based on the mag/lev design to take friction out of the rotation.

    NEODYMIUM MAGNET LEVITATION Vertical Axis Wind Turbine

    [ame=http://www.youtube.com/watch?v=PfZUmbxzUM4]YouTube - NEODYMIUM MAGNET LEVITATION Vertical Axis Wind Turbine MAGNETIC LEVITATION[/ame]

    Link 2- set up multiple vertical axis with no expensive tower, roof mount, that will have rotation no matter which direction the wind comes from and that can handle severe gusting like we get here, freak gusts 50 to 70mph (note, though we like these winged ones made of a boat repair type fiberglass product, I doubt they can survive the gusts we have)

    Vertical Wind Turbines Santiago, Dominican Republic

    [ame=http://www.youtube.com/watch?v=ayGQyo616Ns]YouTube - Vertical wind turbines Santiago, Dominican Republic[/ame]

    Link 3- user made verticals from metal barrells, but alternate the fin cuts so each one it working counter to the one beside it in pairs to increase wind force between barrels just as you would get a jet effect between two buildings close together, squeeze it and force increases. We plan on changing the design to generator on top, levitated over magnets for ease of turn and securely anchoring the low-rpm generators to the type of structure shown in the Santiago link. It will give better maintanence access to the mechanicals, and the secure mount should keep them quiet. The structure mount also allows weatherheads to cover the mechanicals and take the belts out of direct sunlight. Yes I know belts break, but they also will be readily available if any pulse takes out a vehicle, and there are tons in wrecking yards. In a pinch, leather or hide strips braided will work. (haven't worked out a manual brake on this yet, suggestions??)

    Gwindoline - vertical axis wind turbine

    [ame=http://www.youtube.com/watch?v=vCcHKikC8I4]YouTube - Gwindoline - vertical axis wind turbine[/ame]

    Link 4- a low-rpm generator that makes 12volt at 40rpms, that is the icing on the cake, just remember a charge dump is necessary with wind to keep from over charging your batteries

    Hurricane Cat 5 MARK I Low Wind Wind Generator PMA

    Hurricane Cat 5 MARK I Low Wind Wind Generator PMA
     
  19. CulexPipiens

    CulexPipiens Still waiting for the zombies.

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    Interesting suggestion... I'm quite familiar with them as they are involved in my day job, but had not thought of using one for a disaster... instead I was focusing on the solar panel aspect.

    The long term idea is that I can have power in the even of an outage and with surplus feed back to the grid... but if the big one happens, I'd still have some basic power capabilities (lights+) along with working refrigeration... and would continue to have this even if power never came back on.

    Utilizing a UPS and a set of solar panels/wind to act as an alternate to the grid charger might be a viable alternative. I'd have to look for something that would play nice with future battery needs but it just might work.

    Thanks for the nudge to look at this from a different angle.