is there any difference in using cheaper or expensive AA batteries?
402898
You are doing the experiment right? I advise you to buy 2 portbale flashlights to put the Batteries in. Make sure they are the same brand of flashlight.\n\nFlashlight A: Cheap Batteries\n\nFlashlight B: Expensive Batteries\n\nTurn the Switches on and check them every 45 minutes. Once you see one of the lights go dead, you know which batteries are not good. I tried my best to give you a suggestion.
550137
It depends on the conductivity of the metal and how long they're connected to each other.  If you hook them up with one small wire, the wire will get hot and possibly burn after some time.  However, if you do it for a very short time, it won't be a big deal.  It's not good for the battery, sure, but it won't kill you.\n\nHere's a mildly interesting experiment.  Tune your AM/FM radio to any frequency.  Take a 9V battery and a nickel (or quarter) and tap the battery so the nickel touches both leads.  You'll hear your taps on the radio.  Explanation of this can be found in the link below.
845830
I have 6 of these exact cameras.  I use rechargeables in all of them (this will save you big bucks in the long run) but when I hook up a solar panel it does not seem to help (if anything I would say it drains it faster, and yes I have the polarity correct)  I charge the batteries at home and swap them up when I can.  There are a few things that might be the problem.  One is old batteries, after a while the rechargeables just don't hold a charge and you need to replace them.  Two if you have the camera set to video it sucks alot of power from the battery, so try switching to still photos.  Three if you are getting alot of night time shots the flash will drain the battery, try to reduce the time between photos.  Last but not least I believe that some cameras are just not as good as others, I have a few that will last for a month and take 500 pictures and I have others that will die in a few days with less than 50 pictures.  I am not sure if moisture in the area affects the life or not but my camera in the swampy area always dies first.  Also you will get less battery life in the winter time when it is cold. I know I didn't really answer your question but at least you have some thoughts based on experience.
776490
'good' and 'affordable' are both relative terms, but you might give Edmuns Scientific a try, they are having holiday sales, are reputable, and i never got any duds from them. Once you look there, you may totally luck out and find one you get the specs for on ebay.
762945
Rechargeable batteries.
549008
I'd recommend a 36 or higher.  Keep in mind at the top speed setting the battery life of an average deep cycle battery will only be about 2 hours.  You might get a little more time out of top-of-the-line deep cycle batteries (like the Batteries Plus Optima).  I'd suggest getting two batteries (make sure they're deep cycle batteries, regular car batteries will drain much, much faster) and hooking them in parallel.  This will double the time you can spend on the water.
709887
The battery voltage is mainly a function of the metals used for anode and cathode. The lemon merely provides the electrolyte through which the metals can exchange ions. The copper-zinc combination typically used for lemon batteries generates a bit less than a volt.
1095215
The above answers about using a voltage regulator sound ok.  Just make sure to check out the regulator's data sheet so that it can safely regulate what DC voltage you are giving it (though with this 12V case you shouldn't have a problem).\n\nAlso, when a battery is rated at 12V, 30A the battery doesn't necessarily output 30A at all times; that is just a full load rating given for safety reasons (don't want to overload the battery).  The battery is a constant voltage source so you can certainly have a load that pulls much less than 30A.\n\nWidth of wire?  You shouldn't be too concerned with this at these low voltages.  Just use breadboard type wire (around 22 AWG I believe).\n\nAlso, one final comment from me... why use a car battery when you can use a more convenient source of DC voltage?  If you want something that can conveniently power your IC's try one of those nifty AC/DC plugs that charge cell phones and the like.  They are rated in various output voltages and can surely supply all the current your IC's will need.  Just cut off the DC plug end and strip the wire.  Boom, now you have DC voltage for your breadboard supply terminals or whatever.
623921
Just use standard. Even though the others recharge. After you use them the charge doesnt hold as long and it becomes a hassle keeping your equiptment working.
520542
yes they will hold a charge longer.  batteries natually burn off a small amount of energy due to an imperfect storage method.  putting them in a colder environment slows down the chemical reaction responsible for this.
112178
no, It merely helps to conserve the the battery.  Even you you freeze it to near absolute zero, batteries typically aren't made of superconducting materials so there would be no beneficial effect.\n\n^^
1078524
I once read about a device with which reconditioning may be achieved 90% of the time on some types of batteries by applying a very brief, high voltage pulse (kinda like a camera's flash system) across the terminals of individual rechargeable cells.  I tried an improvised version of it with NiCD and sealed lead batteries, and it seemed to work most of the time.  I couldn't find plans for the device when I searched just now, though, so I can't really tell you more than that.  Unless you're knowledgeable in the field of electronics, I suggest you just get another battery because the method of recycling I just described may be dangerous.
442134
Sure they can be useful.  If you're camping where you don't have access to electricity, for instance.\n\nThere are problems of course.  A bright flashlight uses a lot of power and there isn't enough surface area for solar cells to capture much energy throughout the day.  So you get a few minutes of use from a whole day of charging.  The newer LED flashlights go a long way to fixing that, though.  And usually it's not a problem because you don't usually need flashlights every night for long periods of time.\n\nAlso you really would want to charge the flashlight outdoors because there isn't very much energy in indoor light.  Sure it's enough to charge a tiny calculator battery, but flashlights need a lot more.  But leaving it outdoors exposes it to the heat/cold/rain/snow/wind/thieves.\n\nDon't store it in the toolbox. :)
308877
you can get 16 AA batteries for $9!!!!!! anyway, i guess they're water birds. wings are built for underwater type penguin events, what those consist of, i'm not quite sure
162542
AC has less loss over longer distance so is better for wide-area power distribution.  It is also better for high-voltage appliances with high amperage demands (like electric stoves, ovens, dryers, etc.).  Also, before the advent of reliable quartz crystals and such, AC provided a reliable timing source to synchronize signals for televisions (AC in U.S. operates as 60Hz) that is was much more difficult to obtain with DC.\n\nHowever, for local low-voltage, low-amperage power DC is more efficient as most of the types of devices that fit into this category cannot utilize AC directly - they need to convert AC to DC.  It would be more efficient to have a single DC power source using step-down transformers to adjust voltage, than have a bunch of separte AC/DC converters.\n\nIncandescent light bulbs don't care which type of current they are powered from (although LED's do).
263714
The best project will be one that has some interest to the 8th grader. So my granddaughter likes animals. But my youngest boy likes photography. So a pinhole camera would bore my granddaughter but would have caught the interest of my son.\n\nThat being said... Here's an easy one. Go to a store and find some cheap analog clocks (clocks with hands) that run on a single AA battery. Then go to Radio Shack and get some battery holders and some "aligator clip leads" -- short wires with clips on either side. And get a bunch of different brand batteries of different sizes (if you are trying to get by simply, use only AA batteries and then you just need the clocks and the batteries).\n\nTake off the battery covers and hook up the battery holders to the clocks with the clipleads (unless you are only using AA batteries). Then put batteries in and see how long it takes for the clocks to run down. This may take a long time. If you are short on time, try this. Get a flashlight bulb at radio shack and put it across the battery with the clock. So this way the battery is running the clock and the flashlight bulb at the same time. Note the time on the the clock and check it every day to see when the clock stops. You can graph the results easily.\n\nQuestions (form a hypothesis and answer one or more of these):\nWhat lasts longer, a AA, a C, or a D battery?\nWhat brand of battery lasts longer?\nWhat lasts longer, a standard carbon-zinc battery or an alkaline battery? What is the cost difference per unit? Per run time?\n\nA little research on the internet about how batteries are built, and the different technologies (carbon-zinc, alkaline, nicad, NiMh, lithium, lead-acid) and you have a great project.
287049
I have used several, and in my experience BD logic is the most INACCURATE and Freestlye Flash is the most accurate.  The BD logic could have killed me if I believe it's readings, giving me high results when I was low and vice versa.\n\nThe Freestlye Flash I have compared to the lab, and it is almost always exactly the same.\n\nOneTouch Ultra is good too, but I prefer the Flash for it's small size and small amount of blood.