Backyard Theatre setup

freakin out
freakin out Registered Users Posts: 14
My first post, so take it easy on me!

I'm looking at a little project that I realize is impracticle from a cost standpoint, but am doing for fun and convienence. Long-story short: I want to put a couple small panels on my shed, to power up a "mobile entertainment center" that will consist of a couple deep cycle batteries, 12v car stereo with dvd, speakers, 1000w mod-wave inverter and 300w Epson projector all in a wheeled garden wagon used as a self contained unit to project dvd's outdoors.

Idea: Build a battery box (plywood?) that will hold at least two 12v deep cycle batteries in parrallel and will fit in my wagon. Have these power up a 12v stereo the will play the dvds and power the speakers. They will also power the inverter, that will provide 110v power to the projector. Mount panels to the shed, where the wagon will be stored when not in use, to keep batteries charged. Wires coming out of controller whould be fitted with Anderson connector ( or similiar disconnect) so that wagon could be easily disconnected when needed.

Things I already Own:
2 Sunforce 15 watt 12 v panels
1 sunforce 10 amp digital charge controller
1 B&D (vector) 1000 watt inverter
1 Epson S5 projector
Car speakers
four wheeled yard wagon
misc fuses, connectors, switches, wires (including some 4/0 welding cable) and 12v LED lights

Things I know I need
Car/Marine stereo head unit with dvd
Battery ( batteries)

Things I think I need
some sort of Automatic Over Discharge protection so the 12v stereo can't run batteries down too far.
Possibly a 12v amp to boost the sound that the speakers put out. won't really know that until after its made and used.

Questions I already have
Inverter: will modified sine wave work for this application? At this point the projector is the main thing I plan to use, but I'm sure I'd put this cart to use to run lights and such during a power outage, or to run small tools in the shed.
Batteries: I was thinking a couple of $60 Costco deep cycle batteries would be adequate to run the stereo and projector for a couple hours at a clip. What do you guys recommend?
Panels/Controller: Will the two 15w panels be enough? I don't care so much about the recharge speed, because the reality is I would probably use this twice a month on average.

What do you guys think of my plan? Any recomondations, problems, or concerns? This is fairly new to me, so I have no doubt that I am forgetting or oversimplifing, which is why I am here looking for help. Thanks in advance
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Comments

  • James
    James Solar Expert Posts: 250 ✭✭
    Re: Backyard Theatre setup

    have you determined the power requirement for the projector yet? that appears to be a substantial load on the inverter. delicate electronics (LCD projector might not like MSW inverter

    also; the stereo/amp setup (12 volt?) can pull heavy peak (spike) loads from the batteries, maybe affecting the inverter low voltage shutdown.
  • freakin out
    freakin out Registered Users Posts: 14
    Re: Backyard Theatre setup

    the projector is 4 or 5 years old, not one of the newer HD jobs.
    from the spec sheet it uses 248W running ( 4.1W on standby)
  • freakin out
    freakin out Registered Users Posts: 14
    Re: Backyard Theatre setup
    James wrote: »
    also; the stereo/amp setup (12 volt?) can pull heavy peak (spike) loads from the batteries, maybe affecting the inverter low voltage shutdown.

    So would it make sense to just put the Inverter on one battery ( or string) and the 12vdc stuff on another? I have two solar panels, so all i would need is another controller to accomplish this
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Backyard Theatre setup

    The mistake most people make is to overestimate how much power a solar PV system can supply and underestimate their loads...

    In general, lets assume you run this system in the summer (nice weather) and have 5+ hours of full sun equivalent per day (you may have 6+ depending on where you live). 2x 15 watt 12 volt panels, assume ~0.52 system derating (yes, about 1/2 the rated power of panel+losses through controller, battery charging, AC inverter to power load):
    • 2x 15 watts * 1/0.52 derating * 5 hours of sun per day = 78 WH per day
    Assume you want to run the system 2 hours a night:
    • 248 Watts * 2 hours per night * 1/78 WH per day = 6.4 days to recharge
    So, it would take ~1 week to recharge from 1 night of use...

    In general, that is too long of time--Batteries with low charge rates tend to sulphate (the longer time they spend below 75% state of charge, the more the batteries sulphate), lack of "stirring" of electrolyte, and battery self discharge (can become a significant load in itself).

    And lastly, the Sunforce panels are, typically, amorphous panels with poor long term performance.

    Also, the marking on loads tend to overestimate the actual power used. So, using a Kill-a-Watt meter or equivalent can help you measure actual power usage over time.

    As a reference, here is a thread that talks about designing/building a small solar PV system:

    Emergency Power

    Normally, we start from measuring/defining the loads, then sizing the battery bank (true deep cycle, not automotive or marine type), then size the inverter and solar panels.

    For any off-grid/solar PV system, conservation and knowing the loads is the best point to start from.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Backyard Theatre setup
    So would it make sense to just put the Inverter on one battery ( or string) and the 12vdc stuff on another? I have two solar panels, so all i would need is another controller to accomplish this

    You really, really need to get a handle on the load requirements. Both in terms of how much will be drawn and for how long. That's the only way to size the battery bank. Once you do that I'm sure you're going to find that 30 Watts of panel is insufficient to do anything.

    Example:

    248 Watts for the projector * 2 hour movie = 496 Watt hours. Divide by 12 Volts you get 42 Amp hours. At 50% DOD you need 84 Amp hour battery just to run the projector for two hours. To recharge that battery you need at least 5 Amps * 14.2 Volts = 71 Watts of panel. See what I mean? That does not include compensation for losses in system, such as panel derating.

    Darn loads add up fast! :cry:
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Backyard Theatre setup

    And all this to be powered by a total of 30 watts PV?
    I don't think so sir - - - -
    That's not much more than a trickle / maintenance charge for your two batteries.
    Considering all system losses, you'd do well to have roughly 50 watt hours per day to work with, enough to run your system for perhaps 10 minutes. Assuming lots of sun.
    Your batteries will end up having a very short life due to lack of being properly charged.
    You've got some serious loads that are going to require serious PV.
    Your loads will be sucking probably 25 amps per hour out of the batteries, while the PV you have would be doing well to be pumping in 2 amps - - or less under full, dead-on sun for about 4 hours a day.
  • freakin out
    freakin out Registered Users Posts: 14
    Re: Backyard Theatre setup
    And all this to be powered by a total of 30 watts PV?
    I don't think so sir - - - -
    That's not much more than a trickle / maintenance charge for your two batteries.

    Ok, then how about if I simply added at 110v charger into the mix? I could show my movie then afterward wheel it up close to the house, plug into 110v charger overnight, then in morning put back into shed, plugged into my 30w panels for maintence/trickle until the next use. Does that make sense?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Backyard Theatre setup
    Ok, then how about if I simply added at 110v charger into the mix? I could show my movie then afterward wheel it up close to the house, plug into 110v charger overnight, then in morning put back into shed, plugged into my 30w panels for maintence/trickle until the next use. Does that make sense?

    Considering the high cost of solar panels, charging off AC is much more practical.

    Sometimes I want to shoot those people who go around talking about "free" power from the sun. :grr
  • freakin out
    freakin out Registered Users Posts: 14
    Re: Backyard Theatre setup

    So if I am following what everyone has said so far, I think the solution might be to introduce a/c charging into the mix. I could charge the batteries with an a/c charger after using them for any period of time, and still use the small solar panels to maintain them. I imagine this would be more cost effective than upgrading my cheapo panels.
    BB. wrote: »
    Also, the marking on loads tend to overestimate the actual power used.

    If the 248w projector load is in fact overstated, doesn't that actually play into my favor? If i "design" a system based on an overestimated consumption rate, it should give me some wiggle room. while I totally understand what you are saying, I think my project is slightly different than most as I'm not really trying to squeeze out the most cost effiecenct solution so I can hit my return on investment as soon as possible.

    As far as run time goes, two hours at a time between charges is would be what I'd like to get out of it. Most of the movies we show are kids movies that run 90-100 minutes

    I hope I'm not coming across like one of these guys that thinks they have all the answers and just wants approval, because that couldn't be further from the truth. I really appreciate any and all insight, suggestions and criticisms. I know just enough to be dangerous, so thank you again
  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: Backyard Theatre setup
    Ok, then how about if I simply added at 110v charger into the mix? I could show my movie then afterward wheel it up close to the house, plug into 110v charger overnight, then in morning put back into shed, plugged into my 30w panels for maintence/trickle until the next use. Does that make sense?

    This is exactly what you should do. Your panels will be perfect for a maintenance/trickle charge in-between uses, bulk charging overnight just after use from A/C.

    You'll probably want two deep cycle batteries, ~100 amps each @ 20 hour rating, in parallel. So that gives you 200 amps @ 12 volts, but you shouldn't discharge a battery more than 50% most of the time so you really have about 100 amps available to you. Buy them together, always charge them and use them together for best life.

    Assuming 300 watt load for 2 hours, 600 total, @ 12 volts thats 50 amps or 25% discharge, giving you headroom for longer movies or to use this to power a light or two and TV when the power is out.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Backyard Theatre setup

    Yes, you are correct, the projector probably uses less power than you think.

    However, using an msw inverter could cause the load's power usage to go up a bit over a tsw inverter. But a tsw inverter tends to be somewhat more inefficient than a msw inverter.

    In the end, measuring your loads and taking other losses into account is important to have a successful setup.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • freakin out
    freakin out Registered Users Posts: 14
    Re: Backyard Theatre setup
    Example:

    248 Watts for the projector * 2 hour movie = 496 Watt hours. Divide by 12 Volts you get 42 Amp hours. At 50% DOD you need 84 Amp hour battery just to run the projector for two hours.

    Great, so it sounds like if i got two batteries, at least 100ah each I should be able to run the projector and 12v car stereo/dvd for 2 hours.

    Someone else mentioned that the 12v stereo and amp (if needed) could spike and cause the inverter to shut down thinking the bat's were below 10.5v. would it make sense then to have the two batteries wired up indepentant of each other rather than in parralell, so that one battery powered the inverter/projector only, and the other powered the 12v headunit and amp? I'm thinking that this would also give me the flexability to mix capacity sizes if i found that i needed, since they weren't tied together. The downside is that I would have to charge them separetly, but it really isn't that big a deal if the tradeoff is a more reliable system
  • freakin out
    freakin out Registered Users Posts: 14
    Re: Backyard Theatre setup
    BB. wrote: »
    However, using an msw inverter could cause the load's power usage to go up a bit over a tsw inverter. But a tsw inverter tends to be somewhat more inefficient than a msw inverter.

    Thanks Bill, but now you really have my head spinning! Are you saying I need to test the projectors/inverters combined load to properly size the batteries? I should have paid more attention in math class
  • Seven
    Seven Solar Expert Posts: 292 ✭✭
    Re: Backyard Theatre setup

    I would like to add a few things. First of all you are talking about sending a signal from a vehicle radio/dvd deck to a home projector. You had better be sure the output from the car deck is exactly matched to the input for the projector. It may be different like the ohm impedance for car speakers at 4ohm and home stereo stuff is typically 8ohm. It may be the same. What you may want to do is connect the projector to a laptop instead. We have done that camping and just used a sheet hanging on the side of a trailer for the screen.
    If you are set on the car deck, I have a suggestion. Mount the deck in a decent sized beverage cooler. One with a couple of wheels on it. Mount a couple of 6x9 speakers in the cooler as well. All visible from the outside. Get some reasonable 6x9s, nothing with a double stack magnet. The reason for no double stacks is the fact that the cooler will act as a sealed box and will enhance the bass sounds from the speaker, too much bass and the lid will rattle. Find a cheap 12v jump start box from pep boys. You can find them on sale for half the price of the battery itself. Take it apart and remove the U1 battery from it, as well as the little charging board. Remount these parts inside the cooler. Right now what you have is a portable stereo system. That little U1 battery will run that deck, powering those speakers for several hours. You could put one of the little battery minder solar panels on the cooler to keep the little U1 going a while longer. The $20 ones.
    Side note… As you might have guessed by now, I have built a few of these type systems. The first ones I made had the radio on the inside, not mounted to the front because we would put it in an inner tube and float down the river with it. I used $20 sets of speakers on both sides of the cooler so I didn’t care if they got wet. They sound better than you would think.

    Use your garden cart for the big batteries to just power the projector.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Backyard Theatre setup

    Or just use 1/0.85 to estimate the efficiency of a genetic inverter to increase the "248 watt load" to the 12vdc load power/current.

    I am on my phone right now, so it is pain to type a bunch of math and links.

    I can do more later today. But if you are within 20% or better with your estimates, that is pretty much dead on for solar.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • freakin out
    freakin out Registered Users Posts: 14
    Re: Backyard Theatre setup
    Leper wrote: »
    I would like to add a few things. First of all you are talking about sending a signal from a vehicle radio/dvd deck to a home projector. You had better be sure the output from the car deck is exactly matched to the input for the projector. It may be different like the ohm impedance for car speakers at 4ohm and home stereo stuff is typically 8ohm. It may be the same. What you may want to do is connect the projector to a laptop instead. We have done that camping and just used a sheet hanging on the side of a trailer for the screen.
    If you are set on the car deck, I have a suggestion. Mount the deck in a decent sized beverage cooler.

    Not dead set on a car deck at all. I just thought it would be more effiecient since it's already 12vdc, has am/fm built in for listening to a ball game, would act as a dvd player and it would give me enough sound. I thought of using a laptop but I fear I will get no where close to the volume I need. I have also thought about something similiar to the cooler idea, but it defeats one of my main goals, which is to not have any wires laying around on the ground. maybe i can get one of those things that will wirelessly trasmit the sound over the fm airwaves ( fm modulators?). if i did that i could start my own drive-in!!
  • Seven
    Seven Solar Expert Posts: 292 ✭✭
    Re: Backyard Theatre setup

    A set of powered computer speakers would give you all the sound you need. I used a set that cost $40. Don't know the amp draw though.
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Backyard Theatre setup
    Ok, then how about if I simply added at 110v charger into the mix? I could show my movie then afterward wheel it up close to the house, plug into 110v charger overnight, then in morning put back into shed, plugged into my 30w panels for maintence/trickle until the next use. Does that make sense?

    Why don't you just run an extension cord from the house and power everything off the grid?
  • freakin out
    freakin out Registered Users Posts: 14
    Re: Backyard Theatre setup
    ggunn wrote: »
    Why don't you just run an extension cord from the house and power everything off the grid?

    That's what I do now. We usually invite a bunch of neighborhood kids over when we show a movie. Trust me when i tell you, they rarely sit still: Kids and cords don't mix well. Having everything in one self contained unit would make set up and take down a breeze. Plus having it mobile will allow me to take it cul-de-sac, lake. etc. I could bring it up close the house during a power outage and run a cord in the house to run a couple lights or the coffee pot when it's too early/late to wake the neighbors with my genny.
  • freakin out
    freakin out Registered Users Posts: 14
    Re: Backyard Theatre setup
    Leper wrote: »
    A set of powered computer speakers would give you all the sound you need. I used a set that cost $40. Don't know the amp draw though.

    Something to think about for sure. Although i like the idea of mounting a $150 splash resistant marie stereo/dvd over sitting my $800 laptop outside, in the dark, with a bunch of sugared up elementary school kids running around.
    I will deffinetly look into the ohms though for the video connections, i would have never thought of checking that. thanks
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: Backyard Theatre setup

    If the kids hadn't already seen the quality of the projector, I'd be tempted to try one of the pocket LED Digital Video Projectors and run everything of DC current, You'd have to rip the movies (not strickly legal for library or rental movies) but you could run a DC DVD player into one as well.

    From a very high quality, MPro150, that gets passing remarks Here.

    Or, A Cheap alternative, Eyeclops, that gets good marks for the price Here.

    These will get in you power draw range you could charge from your panels, maybe charge 10- 10amp D cell NiMH, that could run either of these and a dvd player and low power speakers for a few hours. NiMH can be somewhat abused, they can handle upto a 10% constant charge sheding the overcharge (as heat) with minimal damage to the battery. I would verify this with any cells you purchase for such a project.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • freakin out
    freakin out Registered Users Posts: 14
    Re: Backyard Theatre setup
    Photowhit wrote: »
    If the kids hadn't already seen the quality of the projector, I'd be tempted to try one of the pocket LED Digital Video Projectors and run everything of DC current.

    Great Idea, but not sure it will cut it. A friend of mine has a similiar projector and the biggest problem with these for my application is that you have to wait until it's really dark to see the picture at all. my kids and their friends are pretty young so if i have to start the movie later in evening, a lot of kids will have to go home before it's finished. the other problem is I've been showing outdoor movies for a few years now with my current projector, so it's hard to get away with a downgrade (kid's are tough critics) . since I have a projector already, it might make more sense to spend the $250+/- on a stronger panel rather than a weaker projector, but i appreciate the suggestion.

    I have no problem with the idea of a/c charging, and using my little panels for mantaince/trickle use. The things I still need to figure out is if the A/C projector and D/C dvd will play nice, and if i should wire the two batteries in parallel, or seperate them with a/c hooked to one, and d/c stuff to the other. I have been thinking that if i wire them seperate i might be able to get away with using a smaller capacity (cheaper) battery on the stereo side.
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Backyard Theatre setup
    I have no problem with the idea of a/c charging, and using my little panels for mantaince/trickle use. The things I still need to figure out is if the A/C projector and D/C dvd will play nice, and if i should wire the two batteries in parallel, or seperate them with a/c hooked to one, and d/c stuff to the other. I have been thinking that if i wire them seperate i might be able to get away with using a smaller capacity (cheaper) battery on the stereo side.
    I don't see how you have anything to gain by splitting the DC load. The capacity you need is the capacity you need whether it's in one battery or two.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Backyard Theatre setup
    ggunn wrote: »
    I don't see how you have anything to gain by splitting the DC load. The capacity you need is the capacity you need whether it's in one battery or two.

    He's concerned about the possibility that the DC equipment may pull so much current in a "spike" that the apparent Voltage at the inverter will drop below cut-out, shutting down the show.

    If the batteries are large enough this shouldn't be an issue. It is in fact more likely to be a problem with the systems separate, as two batteries in parallel obviously have greater surge capacity.

    Me, I'd go all AC and make it easier. But I'm old and lazy. :p
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Backyard Theatre setup

    If you go with a flooded cell battery, the maximum continuous steady state discharge rate is usually C/8...
    • 248 watts * 1/0.85 inverter eff * 1/12 volt bank = 24 amps average
    • 24 amps * 8 rate of discharge = 192 Amp*Hours
    Typical rate of charge for a solar charger is around 5-13% with ~10% recommended for "tall" cased batteries (an AC charger can be larger, but 10% - 30% of Capacity is fine):
    • 192 AH * 0.10 rate of charge = ~19 amp battery charger nominal
    • 192 AH * 0.05 rate of charge = ~9.5 amp battery charger minimum
    Solar panel size at 10% rate of charge:
    • 192 AH * 14.5 volts charging * 0.10 rate of charge * 1/0.77 derating = ~362 Watts Nominal
    • 192 AH * 14.5 volts charging * 0.05 rate of charge * 1/0.77 derating = ~181 Watts minimum recommended
    C/8 is an "8 Hour" capacity battery bank... For normal operation, we recommend not going below ~50% state of charge--So such a bank would power your setup (at ~248 watts) for four hours.

    You can power up to 80% total discharge of 0.8*8hours=6.4hours (or closer to 6 hours). Going below 20% state of charge is not recommended as it can permanently damage the battery bank.

    If you are only doing this once a week during nicer weather--Going below 50% state of charge is probably still not going to be reason the batteries eventually die--Age will probably the reason (not enough deep cycles of ~500 cycles or so of life vs aging).

    Deep Cycle Battery FAQ

    Picking an inverter. FAQs:

    All About Inverters
    Choosing an inverter for water pumping

    For a 12 volt system under 300 watts load--The MorningStar TSW 300 watt 12 volt / 115 VAC inverter is hard to beat.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Backyard Theatre setup

    Me, I'd go all AC and make it easier. But I'm old and lazy. :p

    I'm older and lazier. I'd run an extension cord to the house and throw a rug over it. ;^)
  • freakin out
    freakin out Registered Users Posts: 14
    Re: Backyard Theatre setup
    ggunn wrote: »
    I'm older and lazier. I'd run an extension cord to the house and throw a rug over it. ;^)

    Yea, I may just have to concede the fact that my idea was even less practicle than I had originally thought.

    I am still in love with the idea of putting everything in the wagon, so I may just build something to hold all my gear in an organized fashion, that I can wheel out and run an extension cord to when needed. I may still get a single battery and mount a 12v car stereo and speakers, just to play music or listen to a ball game when I am fooling around in the backyard ( like a kick-ass boom box on wheels). I'd also like to add some 12v LED's to use as task lighting when needed. I could also add my inverter so I can plug in a tool or a couple 110v lights during a power outage. I can still use a/c to charge it after a long use, and use my "toy" pv panels to keep it topped off between uses.

    Thanks for killing my dream ;) , at least now I'm a little better informed and didn't have to learn the hard way (expensive way) like I usually do!!!!
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Backyard Theatre setup
    Thanks for killing my dream ;) , at least now I'm a little better informed and didn't have to learn the hard way (expensive way) like I usually do!!!!

    Hey, that's what we're here for; dream killing. :p

    Better to find out the awful truth before you spend the money. A large number of the posters here join up after-the-fact and ask; I just spent mega $ on this solar power system, why doesn't it work? The answer is usually because 45W of panels, one car battery, and an MSW inverter will not run a 5000 btu AC unit no matter how much the stuff cost.

    Define your goal. Do you want the portability? That's key. If you really need/want something then that is what determines the value of going for it.
  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: Backyard Theatre setup
    ...and if i should wire the two batteries in parallel, or seperate them with a/c hooked to one, and d/c stuff to the other.

    Keep them in parallel. Look up Peukert Efffect, here is one link describing it: http://www.smartgauge.co.uk/peukert2.html

    Basically, the larger your battery, the more amps you can pull from it compared to smaller batteries that add up to the total of your larger battery. Two 100 amp batteries by themselves will give you 50 amps each (to 50% depth-of-discharge), or 100 amps total. Parallel them and you'll get more than 100 amps out of them.

    Edit: and don't kill your dream. You still have a good reason to not use your extension cord, plus you'll end up with a great overnight power source for a night light and your bedside clock while the neighbors are in the dark.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • NEOH
    NEOH Solar Expert Posts: 74 ✭✭
    Re: Backyard Theatre setup
    techntrek wrote: »
    Basically, the larger your battery, the more amps you can pull from it compared to smaller batteries that add up to the total of your larger battery. Two 100 amp batteries by themselves will give you 50 amps each (to 50% depth-of-discharge), or 100 amps total. Parallel them and you'll get more than 100 amps out of them.

    I think you meant to say amp-hrs instead of amps ...

    ... Basically, the larger your battery, the more amps you can pull from it compared to smaller batteries that add up to the total of your larger battery. Two 100 amp-hr batteries by themselves will give you 50 amp-hrs each (to 50% depth-of-discharge), or 100 amp-hrs total. Parallel them and you'll get more than 100 amp-hrs out of them. ...

    Example: at the "standard" C/20 Discharge Rate you get 20 Hours x 5 amps = 100 amp-hrs and at the slower C/40 Discharge Rate you can get 49 hours x 2.5 amps = 122.5 amp-hrs. So, adding the second battery in parallel, without increasing total amps drawn, will increase the total amp-hr rating to 245 amp-hrs instead of just 200 amp-hrs (peukert effect).

    BUT, if you double the total current draw from 5 amps to 10 amps after adding the second battery in parallel then you will only get 200 amp-hrs (no peukert effect).