Tuesday, July 19, 2016

Q:1 Non Rechargeable Batteries, why do we still use them?

Good evening everyone, this is another new segment where I try to write about question or queries that I was asked and think they are worth writing about. So the very first post is about batteries, rechargeable versus non rechargeable. In this day and age where rechargeable cells are very common why do we still use one time use ones? If you have this question too let's see if I can answer that.


Collection of non-rechargeable AA cells
NiMH AA cells being Charged


Most devices that we use today are powered by rechargeable cells and it is understandable why because even if the rechargeable one will cost you more money to get it will cover that up with it's ability to be used for many times. Even if you have to buy a charger for it and charging will cost you some electricity bill yet your money will be saved because you will be able to charge them and use them for moderately long period of time.


Both rechargeable and non-rechargeable cells have their usage and most of the time in different scenarios. So let me mention some of those scenarios where non-rechargeable cells might perform better and then explain why.
  1. In low drain devices like Infrared Remote Controller, Electronic Calculator, Wall clocks or different other similar gadgets non-rechargeable cells are better. Lets think about the wall clock, you know those clocks that run on single AA cell. If you put a normal AA cell that might cost 1/8th of a dollar it probably will run for a year, put an Alkaline one that might cost you 1/2 dollar and it will run for around 3 years so where is the point of even putting a pricey rechargeable cell! Same thing is true for other products that I have mentioned.
  2. Electronic devices that are hardly used and might sit on the shelf for a long time and you might need them to work right away, in this case Disposable cells will be much better suited.
  3. One thing to remember is the NiMH cells have a nominal voltage of 1.2V where standard non rechargeable ones have 1.5V so in many cases the rechargeable one might be considered to be low in voltage even though it has good capacity left.
  4. Charging NiMH is a bit tricky so you will need a good charger so ultimately you will have to invest a good amount of money if you want to use rechargeable cells as oppose to non-rechargeable ones.
Now let’s think about why. Well the very first reason is self discharge rate of NiMH is much higher than non-rechargeable Alkaline cells. The AA Alkaline cells that I bought last year comes with an expiry date of 2022 and I know for fact that they will even work after that time but NiMH will need to charged up occasionally.

For low drain device it might even be the case where the current that the device drains is smaller than the self discharge rate so really not suitable for low drain devices and if for devices that are just kept for emergency like a flash light if you just keep that like for couple years chances are the NiMH cells will just discharge fully and won’t work when you will need it.

NiMH dumb chargers might not be that pricey but they are not good for the cells and might overcharge and cause them to fail prematurely to avoid this you will need a smart charger and usually those smart chargers cost much more than dumb ones.

Another important thing to remember is the environmental impact, yes primary cells(or non rechargeable cells) might be the the bigger contributor to this although the use of mercury is no longer prohibited so environmental impact is not that severe and as I was saying earlier if an AA Alkaline can power a wall clock for 3 years that impact is really negligible although we should be careful while using these cells, stopping unnecessary usage will be eventually be better for everyone.

Note:

Notice that I have spoken mostly about NiMH, why is that? Because in places where lithium ion or lead acid batteries are used it is very hard to replace them with non-rechargeable ones as the cost will go up significantly for example in mobile phone or laptop or uninterruptible power supplies but for NiMH in low drain application you might even get better value using non-rechargeable cells.

Hopefully this small discussion has given you something to think of.

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