The modest energy of the lemon battery is offset by appearance and smell
The modest energy of the lemon battery is offset by appearance and smell. The modest energy of the lemon battery is offset by appearance and smell.
Recently, a lemon is not understood as a citrus fruit, but an appetizing pack of money - it will definitely be enough to buy a battery. However, ordinary lemon is also capable of producing current - even though the acid in it is not sulfuric, but … Which, by the way? Lemon?
GATHER THE BATTERY
The recipe is known: stick two plates of different metals, for example, copper and zinc, into a defenseless fruit. Why necessarily from different? For the current to flow, asymmetry is needed: the same electrodes will behave identically, there will be little sense from their proximity. But zinc and copper dissolve in acid at different speeds, and the corresponding electrodes acquire different electrical potentials. In copper, it is lower, and electrons will move to it. If you connect the plates to each other, then a voltmeter connected to such a circuit will show the presence of voltage. Funny fact: for the direction of the electric current in electrical engineering, it is conventionally accepted not the movement of a crowd of electrons, but the exact opposite. Thus, in our experiment, the copper electrode receives the “+” sign, and the zinc electrode receives the “-” sign.
Four lemons will be enough to wake up the indicator LED. And how many will it take to spin the starter? Let's estimate. The citrus we tested produced approximately 0.8 V, which means that for a voltage of 12 V, 15 lemons will be needed, included one after the other. And everything would be fine, but the current generated by one, even the most “strong” lemon, is from 1 mA! To squeeze at least a hundred amperes, you need to increase the number of fruits a hundred thousand times - it turns out one and a half million lemons. It is not surprising that, under the hoods, instead of boxes with citrus fruits, lead batteries settled.
The electrodes of the lead battery are also different: the negative is made of powdered lead, and the positive is made of paste of its dioxide. They are no longer immersed in the flesh of a lemon, but in a solution of sulfuric acid - an electrolyte. As the discharge progresses, both electrodes gradually become the same, turning into the so-called lead sulfate PbSO4, consuming sulfur from the electrolyte, whose density decreases. Over time, it is getting closer to distilled water. When both electrodes become the same, you will no longer squeeze any current out of the battery (as well as from a lemon with two identical plates inside).
To charge the battery, an external power source is connected to it. The reverse process occurs: sulfur returns to the electrolyte, and both electrodes are gradually restored to their original composition. But the lemon cannot be recharged like that.
Of course, everything described is a greatly simplified model of a modern battery. To give it vibration resistance, durability, and reduce self-discharge, small amounts of antimony, calcium, and a number of other additives are introduced into the lead alloy. The purity of the electrolyte is very important: even insignificant impurities of copper and especially iron sharply accelerate self-discharge, so you can’t add water from the tap.
The so-called calcium batteries are essentially the same lead, but with a small addition of the mentioned metal. Their advantages: very low self-discharge (this allows you to store already filled and ready-to-use batteries in warehouses) and a lower tendency to boil away the electrolyte during charging (the battery becomes almost maintenance-free).
IT IS FITNESS
In cold weather, chemical processes freeze, so the battery not only gives out worse current, but also refuses to take charge. Hence the unexpected refusals to twist the starter: if the trips are short-lived, the electrolyte does not have time to warm up - the charge does not recover. At the same time, the generator is working properly, but the red light of no charge does not light up. Another winter feature. Remember, we talked about a decrease in the density of the electrolyte and the conversion of the active mass of the electrodes into lead sulfate? Both of these increase the internal resistance of the battery - at high load, a fair part of the volts will remain in the battery, and will not go to the starter.
What else is worth knowing about starter batteries? First, never allow a deep discharge. This will lead to irreversible sulfation of the plates - when charged, most of them will not recover to their original state, which is equivalent to a loss of capacity. Such a battery seems to be charging, it produces 12.6 V, but it accumulates so little energy that it may not be enough even for a single start-up.