AA and AAA Ni-Cd Nikkel-Kadmium battery:
This type was invented in 1898, it was famous until the 1990s when the Ni-Mh became more popular.
1,2V is its nominal voltage, it can only be used limited instead of the normal not rechargeable batteries with 1,5V voltage. They can withstand high current drains. Their capacity is not too big, I do not have good experiences with this type of batteries. They are inclinable to a so called memory effect. If these batteries were not charged fully for a couple of times, then at the next recharge the full capacity became lower. The Cadmium inside them is highly toxic, the European Union has already limited their market.
AA and AAA Ni-Mh Nikkel-metal-hidrid battery:
Their research began in 1967 and they are still popular today, but the manufacturers use Li-ion in more and more places recently instead. Ni-Mh capacity is more than Ni-Cd, they also have 1,2V nominal voltage. They cannot withstand that high drain current as the Ni-Cds. They are not likely to have memory effect. They are also used today in hybrid and full electric cars.
For both the mentioned battery types the electrical devices do not have an easy task to measure the remaining capacity for them. It made me nervous that after recharge I put the Ni-Mh batteries into my camera and it showed after some picture that the battery is now only half full. And as the time went by after 50% capacity the camera said the batteries will be discharged soon. Now I know why this happens. This is in connection with the voltage while they are discharging, which can be followed on the following picture:
On the left is the voltage in mV, on the bottom are the seconds while I was discharging a Ni-Mh AAA battery. It can be very nicely seen that the voltage does not drop consistently like with the not rechargeable batteries, instead in the beginning the voltage drops to 1,2V then it stays there for a long time, and at the end it suddenly drops under 1V. That is why the current capacity cannot be measured accurately by the devices.
They are very irritating at charging as well. There are so called dull chargers for them, which charge them with a small constant current, not watching the voltage in the meantime. They may also overcharge the batteries. On the other hand there are the smart chargers. I do not like them either. Recently the batteries were discharged in my camera and I have put them in the smart charger. One of them was charged for 6 hours, the other was "full" after 10 minutes, however it was empty! I had to discharge it under 1V so the smart charger would recharge it fully. They are a mess.
Li-Ion batteries:
they have begun to develop this type in the 1970s. They went out to the consumer market in 1991 first. They have a much greater power density, they are much lighter than the previous types. They are the stars of the today’s mobile world, they are used everywhere. They are even using them in electric cars.
Their nominal voltage is 3,6-7V. Their voltage drops consistently while discharging so it can easily be measured how much power they have left. They do not have a memory effect, however they cannot be recharged that much like the older types. They are much more sensitive than the others as well. Unfortunately today they can even also be dangerous.
If they get shorted because of some reason, which can be an outside effect or a manufacturing error, they can get hot very fast and a so called "thermal runaway" may begin. This means a sudden overheating which induces a chain reaction inside the cell which can cause an explosion if the battery has a closed sealing package. For instance the 18650 Li-ion cells which are used in the laptop batteries are made in this way. If a cell gets overheated and starts to burn, it will very likely get the other cells to overheat as well. One has to be careful not to leave for example devices with li-ion batteries on the sun or in the car. Their transportation was already limited on the planes because of the fire hazard.
They must not get discharged under a certain voltage (around 3V), because it damages the chemistry inside. They must not get overcharged over the set voltage, as they can overhear and damage the cells. They are very fragile. But there is no better alternative today instead of them. The researches are ongoing to find a safer alternative.
The Li-Po batteries does not differ much from the Li-ion cells, mostly just in their name and the used Anode and Cathode materials. They may have different characteristics.
The recycling of the mentioned batteries is only feasible in huge quantities today, however in the future as the resources will begin to run out on earth, this trash will worth a fortune. After selection of the battery types they are grinded and then on high temperature they get melted and the metals separated then reused.
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