The first customers of electric cars may have known them, the famous lead-acid and Ni-Mh batteries, models that are no longer up to date and have almost disappeared. However, some vehicles still use them, but this technology is however set to disappear for obvious ecological reasons, but also for efficiency.
Today, if you buy a new or even recent electric car, there is about a 99% chance that it carries a lithium-ion battery. In the future, this could obviously change, since many manufacturers and suppliers are working on batteries with other technologies, such as those based on sodium for example.
We have also produced an explanatory subject on the advantages of these new sodium-ion batteries and why they could take precedence over lithium-ion technology.
But before sodium, and even before lithium, the first electric cars were entitled to a completely different technology. These are lead-acid batteries or nickel-metal-hydride batteries. These technologies are now largely outdated, both from an energy and environmental point of view, but they have not completely disappeared.
How are they made?
Lead-acid batteries use two electrodes immersed in sulfuric acid to operate. The positive electrode is made of lead coated with lead dioxide, the negative electrode is made of porous metallic lead.
A chemical reaction between the latter and the sulphate contained in the sulfuric acid leads the charge from the negative electrode to the positive electrode, thus generating a current. This reaction can be reversed, allowing the battery to be recharged when connected to an electrical source.
Nickel metal hydride batteries, on the other hand, have a cathode made of nickel oxyhydroxide and an anode made of a metal hydride composite.
The advantages and disadvantages of this type of battery
These two types of batteries, although different in terms of materials and operation, have similar characteristics. Firstly, they are quite simple and inexpensive to manufacture. On the other hand, they are less flammable than lithium-ion batteries.
However, they have a number of limitations that did not allow them to survive the arrival of lithium-ion batteries, except marginally.
The first limit is their low durability. Lead-ion batteries (used in particular on models such as the Fiat Panda Eletra) undergo between 250 and 500 recharge cycles before their performance drops by 20-30%. Nickel-metal-hydride batteries do a little better, although we’re still in the range of around 500 cycles. To give you a little idea, lithium-ion batteries can “take” two to three times more cycles before a significant drop in performance.
In addition, they both have a low energy density. Lead-acid batteries also suffer from self-discharge, i.e. they lose some of the stored energy, even when not in use.
Nickel-metal-hydride batteries, on the other hand, suffer from the memory effect. They lose their performance if a partial recharge is made or if the charge is restored to 100% when the battery is not completely discharged.
By whom are these batteries still used?
Lead acid batteries are still used in some electric cars, but only on very cheap and very small models. They are mainly found on vehicles produced in China, city cars or even light quadricycles.
Nickel-metal-hydride batteries, on the other hand, are still very common in the automotive world, but are not used by fully electric cars.
They are found instead in hybrid or plug-in hybrid cars. Toyota, for example, has used them for decades for its hybrid vehicles. Since then, the Japanese manufacturer has switched to lithium-ion batteries.
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