I was replacing the batteries in my digital voice recorder and was wondering something. Why do most batteries (AA,D,AAA) seem to have to be placed in a device going opposite directions? Seems only flashlights have them going the same direction?
Any Resident Electricians in the house? Q.E.D?
The cells in most devices are chained up in series to provide a higher voltage than the (usually) ~1.5v supplied by a single cell.
The simplest way to achieve this is to lay two alongside each other in opposite directions, connect + to - at one end and connect the two open ends to the device.
Actually they are the same in flashlights and other devices (positive to negative). As you should have learned in school, each battery has about 1.5 volts of potential. To get three volts, you have to place two in series. In a flashlight, you do this by stacking. Most devices, however, can’t be so long so they have to be side by side. the shortest connections between positive and negative result in placing them in opposite directions.
Because the only way to hook them up without shorting them out is positive to negative.
Putting the batteries in opposite directions side by side means the contacts only have to be thin strips of metal (with springs or whatnot) instead of wires crossing all over.
It’s simple cost savings.
The reason they are connected in series like that, is because it multiplies the voltage.
It depends how they’re arranged, if they’re in a colomn they need to be pointing in the same direction, if they’re in a row then it’s easier to have them in oppoiste directiobns as it means that the postive terminal of one battery is nearer the negative terminal of the other and these are what has to be connected.
rereading my post, I did so without thinking.
You can also hook them up ++ – (parallel) but you will end up with only 1.5 volts total as hooking them up parallel multiplies the amperage, not the voltage.
The positive from one battery toches the negative end of the next battery. In a flashlight they all go in a row with the positive end touching the negative end of the next battery. In a device where the batteries go side by side the positive and negative ends are connected by a small strip of metal and must face the oppisite direction of the one next to it. Picture two flashlight batteries in a row with the positive of one touching the negative of the other. Now turn one battery so they are side by side, but keep the positive and negative ends as close as possible.
Flashlight
-±*+
Other device
-+
+-
And damn all of you and your fast typing.
…Which, in most cases would be achieved by designing the device to accomodate a larger cell.
I was about to correct you, and say it ADDS, not multiplies the voltage: 1.5 + 1.5 = 3 volts.
But if you were thinking that 2 X (one 1.5v battery) = 3 v, then I guess you would say it multiplies, so never mind.
I can’t remember any consumer device that didn’t arrange batteries head-to-toe.
Shhh. Q.E.D.'s sleeping. No need to wake him for this. We’ve got it covered.
Perhaps we should design a battety compartment that includes rectifiers and extra wiring so that no matter which way any of the cells were inserted, the correct power would be achieved anyway…
Oh you guys!! so quick this monday morning…though it’s not morning in the UK is it? Thanks guys! gals?
Well, not really. While it is true the open circuit voltage will stay the same, putting them in parallel will lower the Thevenin equivalent source resistance. This means there will be less voltage drop as the current increases.
[sub]All of this assumes the batteries are “matched” pretty well…[/sub]
So how many of these batteries would it take to power a 1920’s-sty…
Never mind.
This would increase the cost of the device by a penny. And the typical US consumer would go “Oh, this other one is a penny less, I’ll buy that one instead.” (In actuality, dozens of such cost saving “features” are added to products to make them a lot less than a penny cheaper. But the effect is the same. Crappy and cheap wins over good and reasonable nowadays.)
Actually, inserting diodes to auto-correct battery polarity would reduce performance significantly.
There is a voltage drop across a diode junction when it is forward biased (i.e. conducting [1] ) This characteristic drop is 0.7v for some germanium diodes to 0.2-0.25v for the silicon diodes most common today. I’m sure there are fancy schmancy diodes that have a lower forward voltage drop, and other readers will inform us about them.
When the no-load voltage on a nominal 1.5v battery drops below 1.4v, it’s definite heading down for the count. Some devices won’t be able to use it at all (which is why some digital cameras don’t work with NiMH cells, which have a voltage of 1.4v to begin with) others won’t care (TV/VCR remotes often work quite well down below 1v, and I’ve seen people nurse them dow to close to .6v)
While many devices that require a battery voltage of over 1.3-1.4v really need the increased current output at that part of the dry cell (does anyone use those anymore) or alkaline cell discharge curve, almost all of them will have an effective battery life that is several times shorter. You could easliy end up changing batteries 2-5x as often (or more)
[1] There’s also a voltage drop when it is reverse biased. A voltage drop of 100% in fact, since it is not conducting. Well until you reach breakdown voltage, and then all bets are off.