![]() When choosing a battery size (capacity) for our job, remember that it will last longest if it is never depleted by more than half its capacity …in other words, it is never discharged below 50% state of charge (SOC). There are several ways to destroy even a brand-new battery in a week or less – and it is those that we will be taking a look at first …but before we do let’s establish a few general rules for using our battery without causing it any life-shortening damage. To make matters worse, the functional limitations brought about by any one of these damaging events, will frequently trigger a second or third mode of failure. These are the principle maladies which cause either an unacceptable loss of capacity in a battery, or a failure to store or release energy at all. The electrolyte is the agent for chemical reaction – when it is much reduced, or absent, the battery cannot function. The cohesive structure of the lead breaks down allowing some lead to fall away – this deterioration of the plates is known as ‘shedding’.Įlectrolyte – either as a liquid or a gel – decomposes and is lost as gas. This condition is called sulphation – eventually it denies all access to the battery’s storage capacity. The spongy lead plates can become coated in a hard layer of lead sulfate crystals which prevents access to the plates. We’ll be taking a look at charge-voltages later.ĭriven by the movement of electrons, the cyclical passing back and forth of sulphate, between the lead plates and the electrolyte, sounds fairly simple – so what could possibly go wrong? Three things in the main: ![]() Such batteries are, however, provided with a pressure-release valve in case of over-gassing – caused by charging at too high a voltage. Sealing the battery prevents the Hydrogen and Oxygen gases from escaping instead they recombine under pressure, the gases are trapped and are re-absorbed during the discharge cycle. Low maintenance batteries don’t need topping-up – in fact they cannot be topped-up because they are sealed. Wet-cell batteries require topping-up periodically with (de-ionised) water to replace the liquid which has been lost over time. The decomposition of the water in the electrolyte into oxygen and hydrogen gas (electrolysis) is normal during the final stages of battery-charging – but is usually quite limited. The second thing we need to notice is that if the charging voltage is too high, or is maintained for too long another chemical reaction begins in earnest: the water in the electrolyte decomposes into oxygen and hydrogen. Conversely – recharging the battery forces the sulphate to leave the lead plates and return, once more, to the electrolyte forming dilute Sulphuric Acid. That chemical reaction is fairly complicated – but we need only notice a couple of things about it: As power is drawn from a battery sulphuric acid is lost from the electrolyte and combines with the lead plates to form lead sulphate. The porosity of the lead in this condition makes it fully accessible to the the electrolyte, enabling a chemical reaction to occur relatively easily throughout the thickness of the plate as the battery performs its task of storing and releasing energy. The lead oxide and is not solid, but spongy and has to be supported by a grid. Therefore there are six cells in a 12V battery – each one comprises two lead plates which are immersed in dilute Sulphuric Acid (the electrolyte) – which can be either liquid or a gel. In order to understand what is going on inside a battery, we need to know how it is constructed, and what happens when we discharge and re-charge it.Ī lead acid battery cell is approximately 2V. There are also many other kinds of battery chemistries such as lithium, but this information is specifically about lead. This article is specifically about lead batteries.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |