Wednesday, January 23, 2019

Are Dead Batteries Really Dead?

Have you ever used battery operated hand mixer? Or any other battery operated high current drain device (typically one that has a motor inside)? If so, you know that typical batteries don’t last long in those devices. Alkaline might provide better service hour but still not very much.
So, what do you do with those batteries (or cells)? They can’t run those devices for any longer so throw them out perhaps? If you do that you are actually wasting quite a lot of energy. How so? Let’s start the explanation with an image from Wikipedia.

What this picture describes is an AA Alkaline cell that is being drained at 100mA constant current. In other words, you can imagine an Alkaline cell to run a device that consumes 100mA current constantly. If the device you have is designed in a way that cuts off at 1.3V (for sake of explaining) in other words it will not work if the cell voltage drops below 1.3V you are only using the Green Portion of the energy that was in the cell. If, however your device can use up to 1.1V it can use additional blue portion of the graph and as you can see the area has increased a lot. So, further you go down on the voltage more power you can extract from the cell. Although you can not really go below 0.8V because at that voltage or below this type of cells usually cannot provide enough current or majority of devices won’t run below this cell voltage.

Back to my original example, if you get some used cells out of your battery-operated coffee mixer and measure the voltage you would probably see something like 1.2V-1.3V which means they still hold a lot of energy in them. Energy in the blue portion of the graph is still unextracted. So, throwing away such cells is wasteful and not good for both environment and your wallet. You can easily use these cells on wall clocks, if you have good quality ones that can use Alkaline/Zinc Carbon cells down to 0.8V-1V. This way you can extract a lot more energy out of them. 

A cell gotten out of such a mixer can power a wall clock for months or even year in case of Alkaline. Bottom line do make sure you have got the maximum capacity extracted from disposable cells before throwing them out. To ensure this use devices that can go down to such voltages, usually Calculators, Infrared Remote Controllers and Wall clocks can go down to that level. Do keep in mind all of them are not made equally so not all of them will be that good.

Disposable AA/AAA cells start their life at 1.6V and more you can go down more energy you can get out of them.  

Ajanta Wall Clock - Good or Bad?

Ajanta Wall Clock, The Worst one in the Market?

So, I recently went out to buy a wall clock, something cheap with large dial and feeling a bit lazy I went to New Market near Nilkhet. I was hoping to get a Citisun wall clock but couldn’t find one. This place mostly sells Ajanta Wall clocks which boasts as the number 1 seller of clocks in Asia or something. Hesitantly I bought one because previously I had one Ajanta Wall clock and it died within a few years whereas my Seiko Wall clock kept on working despite being older than me. Anyway, took me about 10US$ to buy it. 

Bought it, got back to home and the very same day it stopped working. Turned out the second hand was touching the glass and that made the clock stall. I took it back to the seller, he didn’t replace it simply bent the second hand a little so it wouldn’t touch. Within a week same thing. This time I opened it up and fixed it, after couple days again same story. So, I lifted up the glass a little with help of some small plastic pieces this time it kept on working however as it is no longer sealed dust crept in and dial got dirty. I thought whatever at least it is working but it didn’t work for long. I was a bit curious and measured the voltage of the cell that retired from this clock. It was at 1.35V, which means this stupid clock hasn’t even used most of the energy that was in the cell.

Somewhat disturbed I put in an Alkaline cell (it originally came with Zinc Carbon Cell). Again, after couple months it stopped and voltage of the cell that I got out of the clock was around 1.5V. I plugged in a new cell and nothing happened. After doing some testing I came to conclusion that the clock is gone. So much for the number 1 seller.

Bottom line? I am not going to buy Ajanta clocks, not only they might come faulty but they also will pile up huge number of cells that has a lot of energy left in them. I would much prefer Citisun as a cheap wall clock, yes it does sound like a Citizen clone and Citisun’s calculator does look that way but they are pretty good to be honest.