A part of Celltech Group EN SV Menu Battery schoolBattery School Part 1 Part 1 – Battery type För den som känner sig vilsen i strömförsörjningsdjungeln har vi satt samman en snabbkurs om batterier och laddare. Här finns även en ordlista. Choosing a battery type There are so many things to consider when choosing a battery system. How does it consume power? Does it require quick recharging? What is the ambient temperature during charging and discharging? The desired total longevity? Price? All of these factors are important. Some batteries are used as back-up for critical systems like life support, while others simply keep a light on longer. However, it is always worth investigating the scope, size, and maintenance requirements – in order to make the right investment. First off, it’s important to remember that a battery is an energy converter that stores chemical energy. This energy is converted into electricity when it completes the circuit through an external circuit, load, etc., or conversely takes electrical energy from a charger and stores it as chemical energy. A capacitor can also be recharged with electricity and emit energy, but in this case it is really an electric charge which is stored up. See below for capacitors and batteries. Lead-acid batteries Small and medium-sized sealed lead acid (VRLA, AGM / GEL) batteries, are sometimes called, a bit erroneously, “maintenance-free” batteries. They manage to deliver large currents for a short time, but to get out the battery’s total capacity, the power consumption should be relatively low. The nominal capacity applies normally with 20 hours of discharge, with higher currents (less time) the total capacity becomes lower. Energy density around 30-50Wh / liter or 20-30Wh / kg, nominal cell voltage is 2V. Lead acid batteries provide a cost effective solution and are relatively easy to load and take care of. They have no so-called memory effect, can be recharged even when they are not entirely empty, but should never be left discharged, or they can be destroyed in a short time. NiCd NiMH Lithium-ion Lithium-Polymer Lithium-ion Polymer Lithium-ion iron phosphate Rechargeable alkaline cells (RAM) Lithium (primary cells) Smart batteries, SM Bus, BMS, SBS, etc. Power consumption is decisive Ordinary alkaline cells are sometimes used in for example a portable two-way radios instead of rechargeable cells. These have on paper a higher capacity than a NiCd or NiMH cell of the same size. For example an AA / LR6 alkaline cell can have 2800 mAh while the corresponding Ni-Cd perhaps has around 900 mAh but the operating time becomes not always longer. This is because the internal resistance is higher, and the terminal voltage drops rapidly when the battery is charged. The battery is simply not optimized to work with large currents. Even the so-called manganese dioxide battery which is the predecessor of alkaline batteries is sold as an alternative with lower price, most suitable for applications with low consumption Capacitors and batteries, “Supercaps” In some contexts, the combination of a rechargeable battery and a capacitor with high capacitance can be useful. Primary Lithium (non-rechargeable) are connected in parallel too often with capacitors, in order to counteract the short voltage dips that would otherwise arise in the lithium battery when one applies a load after the battery has “rested” for a long time. In conjunction with major effects, in rechargeable systems, like with electric vehicles and in conjunction with energy storage on a large scale so-called Supercaps are often used, which are a special type of multilayer electrolytic capacitors. Very high capacitance from a few F (Farads) to several thousand F may occur and the capacitor can briefly give many kW, at the same time as it can be recharged as quickly. Compared to a battery, however, the capacitor has significantly lower total energy content or energy density, around 2-3 Wh per liter or kg where for example a lithium battery can easily have 100 times higher or more. The effect that can be handled instantaneously, however, is higher for the capacitor; cycling lifespan of capacitors is significantly better than for batteries. The combination of Supercaps and batteries or other power sources often gives good results. Fuel cells A system that directly and continuously converts chemical energy into electrical energy. Can be likened to a battery that can continuously be filled with a fuel. The most common fuel is hydrogen gas which then decomposes electrochemically and generally uses a so-called reformer that converts a hydrocarbon based fuel such as methanol into hydrogen and carbon dioxide. The principle behind the fuel cell stretches back to the early 1800s, but not until the 1950s were more practical fuel cells produced with high effect. NASA and the space program was a driving factor and today you can buy practical, usable systems. The efficiency can theoretically reach more than 80% but in practice usually around 50-60%. Emissions from a continuously operating fuel cell are “clean”, often plain water if the cell for example is supplied with hydrogen. The longevity and economy of batteries and battery systems The lifespan of the various battery types depends on a variety of factors, ambient temperature, depth of discharge etc. A Ni-Cd battery can last 500-1000 cycles or more in favourable conditions, especially for large industrial systems, Ni-MH and Lithium-ion batteries last usually slightly fewer. Many newer Li-technologies, like Lithium Iron Phosphate can be optimized to last through many cycles, considerable resources are being applied and research is being done in this area, especially in relation to electric vehicles. Even lead-acid batteries can be optimized for either cyclic or standby operation, and can in the latter case function for at least 10-15 years. One factor that is important to, for example, lithium and lead technology, is the depth of discharge (DOD), which then is determinate for the overall life expectancy. If you for example utilize only 80% of the nominal battery capacity, you get significantly more cycles in total and a longer life, lower risk of battery failures and so on. Rapid developments make it difficult to give too detailed data and special formulations exist within the different chemical systems. Always consult with Celltech for your current application. Part 2 Contact Visiting address: Kista Science Tower Floor 19 Färögatan 33 164 51 Kista Tel: +46 8 445 78 70 Mail: info@celltech.se Delivery address: Tredenborgsvägen 16 294 35 Sölvesborg Follow us We'll assume you're ok with this, but you can opt-out if you wish.AcceptReject Find out more...