This is a two-part question.
- When I was a kid (and dinosaurs ruled the Earth), batteries were these little things you had to put into something to make it go and then you forgot all about them. One day a long time later the thing stopped working and it took you a while to figure out that you needed to change batteries, as you did it so seldom that it didn’t occur to you.
These days (when kids have no respect for their elders), batteries last hours to days. Sure, they’re rechargeable, and I realize that a modern cellphone or MP3 player does a lot more than the walkman of yesteryear, but still.
So, the first question is: Why do batteries suck these days?
- Battery charge indicators, those gauges that battery-powered electronic devices have to show how much juice is left in the battery. They don’t work very well either. So far in life, I’ve seen two variants:
a) When you put a fresh (or newly charged) battery in, the indicator is at 100%. You turn the thing on, it drops to, say, 20-40% very quickly, and then stays there until the thing stops working due to an empty battery.
b) When you put a fresh (or newly charged) battery in, the indicator is at 100%. You turn the thing on, the indicator stays between 95-100% for a long time, and then suddenly drops to 25% or so, and soon afterwards the thing stops working due to an empty battery.
In both cases, the indicator doesn’t fulfill any kind of reasonable purpose.
So, the second question is: Why do battery charge indicators suck?
Because “a modern cellphone or MP3 player does a lot more than the walkman of yesteryear”.
Because there are no practical outward indicators of dry cell battery charge. There is just not much that you can measure to say how charged a cell is.
Batteries are actually a lot better than they were in the “good old days”. Carbon Zinc type, if you can find them, are no match for Alkaline type either in price or performance. What has changed are current demands on the device. Early transistor devices from the 50’s and 60’s just sipped the juice and battery life was almost identical to shelf life. Modern microprocessers don’t draw much current either but have a steady drain because of LCD displays, memory and so rechargeable packs are preferable. Can you imagine changing a rack of D cells every other day for your laptop??
So they really do that much more, then? And there hasn’t been progress to match in the field of battery technology?
How do battery chargers know when the battery is full? Do they notice that they can’t pump more juice into it?
Non-rechargeable alkaline batteries still exist, and they can contain more power than rechargeable ones. So comparing today’s rechargeable batteries with the non-rechargeable ones from your dinosaur-hunting days is not really a fair comparison.
The rechargeable ones are getting better, though – modern NiMH AA batteries can contain 2600 mAh, which is very close to the 2850 mAh capacity of a good alkaline AA. On the other hand, rechargeable batteries tend to lose their charge over time, so if you are going to compare them you should make sure to get a freshly charged one.
My cell phone lasts about a week on its rechargeable battery, and I leave it on day and night. An MP3 player or walkman may last longer, but that’s because you generally don’t leave it on 24 hours per day.
Actually, I’d expect an MP3 player to need less power than a walkman or CD player, simply because the latter have moving parts. On the other hand, MP3 players often contain only a single AA or AAA battery, whereas a walkman may need two or more larger batteries. Again, make sure you’re comparing apples to apples.
Colour screens are the big energy eaters in modern portable devices. That’s why, when I recently bought an MP3 player, I made sure to get one with a simple monochrome display – a Cowon iAudio G3, which according to the manufacturer can deliver 50 hours of music on a single AA battery. My own experience so far confirms that this is pretty close to the truth (on an alkaline battery). My ancient Sony Discman, on the other hand, needed two batteries and lasted less than 30 hours.
As far as I know, those power indicators work by measuring the output voltage of the battery. On a fully charged battery, that output voltage will be slightly more than the battery’s nominal 1.5V, but as the battery is drained the voltage will go down.
AFAIK, those indicators are normally intended for alkaline batteries, which have a fairly predictable curve so the indicator is reasonably accurate. If the power indicator of your device is designed for alkaline batteries and you put in a rechargeable one, you’ll get inaccurate results. Some devices allow you to set the type of battery in the software, so the indicator will be more accurate.
When a battery is charged, its internal resistance goes up as it becomes full. This can be measured by the charger, so “they realize they can’t pump more juice into it” is a pretty accurate description.
My take on it? Weight.
Back in the old days, things used to use bigger batteries, and more of them - I remember big honking rows of D cells. When was the last time you saw a D cell? Appliences these days are much, much lighter than they used to be, which means their batteries are much, much smaller. Compare the weight of a transistor radio to that of a cellphone, and try to see how much of that weight was power supply Less weight = less battery = less power.
I find batteries great these days. I wouldn’t have devices I do otherwise, because the old one sucked so bad. They were always dead unless they went in five minutes earlier.You can get the older type if you think there great. Look for the cheapest batteries you can find and buy them.
I was thinking about batteries this morning. The first digital camera I bought about 15 years ago had a battery the size of a pack of cigarettes and lasted 20-25 pictures. About 6 years ago the new camera had a battery the size of box of matches and was good for around 100 shots. I bought a new camera last month with a battery the the quarter the size of a book of matches. It’s still going on the first charge after 200 shots.
I think something’s getter better somewhere.
About inaccurate battery level indicators, for NiCd and Nimh batteries the reason for this is that the voltage is pretty constant throuout the discharge till the very end, so it is hard to accuratly measure, Alkaline’s voltage drops off with discharge in a fairly predictable manner.
I don’t know how Li-ion fits into this.
But I agree that batteries are better today, but we are making them do more and making them smaller.