Fullscreen HTML5Med Res (??MB)HTML4

A ll A bout Part 3: by Dr David Maddison Batteries Batteries have been an important part of vehicles from some of the earliest cars, which were electric. They continue to be used for engine cranking and to run accessories in vehicles with internal combustion engines. The latest and greater lithium-ion types are being developed Background Source: once again to provide motive energy. https://unsplash.com/photos/ZZ3qxWFZNRg V ehicles like cars are a major user of batteries today, as are aircraft, submarines and so on, so we will examine some of these applications. We will also cover battery measurements and other aspects of batteries in this third and final part of the series. In case you missed them, the first part in the January issue described the history of battery technology and described common or important battery types. The second article in the last issue had more details on lead-acid batteries, less common battery types, and many still under development. Electric vehicles The history of electric vehicles could be a whole series of articles in itself, but here are some significant highlights. The first electric car (or “electric carriage”) was developed by Scottish inventor Robert Anderson. He invented this carriage between 1832 and 1839. It used non-rechargeable primary cells. Note that there are other claims to this title, but Anderson seems to be the first to produce a full-size vehicle. Rechargeable batteries were invented in 1859, and in 1884, Englishman Thomas Parker developed an electric car. In 1890, William Morrison of Des Moines, Iowa (USA) applied for a patent for an electric carriage he had built as early as 1887. The vehicle had front-wheel drive, a 2.9kW (4hp) motor, a top speed of 32km/h (20mph), 24 cells and a range of 80km (50 miles). The first commercially successful electric vehicle enterprise was by Philadelphians Pedro Salom and Henry G. Morris. They patented a vehicle in 1894 called the Electrobat (see Fig.58). By 1896, these vehicles had been developed to have two 1.1kW motors, a top speed of 32km/h and a range of 40km. They then built some electric Hansom cabs and sold the idea to Isaac L. Rice in 1897, who then incorporated the Electric Vehicle Company in New Jersey. Rice attracted investors and built electric taxi cabs that operated in New York City and surrounding areas (see Fig.59). Fig.58: Morris and Salom in the 1894 Electrobat, the first commercially-produced electric vehicle in the USA. Fig.59: an Electric Vehicle Company Hansom cab in 1904. Source: Bundesarchiv, Bild 183-1990-1126-500 (CCBY-SA 3.0) 44 Silicon Chip Australia's electronics magazine siliconchip.com.au Because of the time taken to recharge the batteries, the depleted batteries were swapped with fully-charged batteries at a central location as needed. The enterprise failed in 1907. Thomas Edison’s first car was a Baker electric vehicle, for which he designed the nickel-iron batteries. The Baker Motor Vehicle Company was based in Cleveland, Ohio and made electric vehicles from 1899 to 1914 (see Fig.60). Jay Leno owns a 1909 Baker & there is a video from MyClassicCarTV featuring this vehicle, titled “Jay Leno’s Baker Electric Car” at https://youtu.be/ OhnjMdzGusc Electric vehicles were quite successful in the early 20th century but interest faded after about 1920. Part of the reason was that road networks expanded dramatically, plus there were large discoveries of cheap oil from which gasoline was derived. Electric cars with ranges of about 80km were fine in urban areas, but the range was unsuitable for intercity travel, at which gasoline vehicles excelled. The availability of suitable batteries limited their range. There was also a lack of suitable control electronics, which would come later, using Mosfets, IGBTs and microcontrollers (among other parts). Until about the 1990s, electric vehicles remained in the realm of specialty uses such as for local deliveries or shopping vehicles, or curiosities. They relied mainly on lead-acid batteries and had much the same range as the EVs before the 1920s. A significant development was the General Motors EV1, introduced in 1999 with a range of 260km using a NiMH battery (see Fig.61). It could not be purchased and was only available to lease. GM inexplicably cancelled the program and eventually, they destroyed all but 40, with the remainder deactivated and donated to museums and educational institutions. See the video titled “Who Killed The Electric Car” at https://youtu.be/ l3OnYjP4FTk – a shortened free version of a much longer documentary of the same name. In 2008, Tesla released the Tesla Roadster (Fig.62), which used a lithium-­ion battery and had a range of up to 393km. This was a major breakthrough because it was the first EV available with an acceptable range since GM cancelled the EV1. siliconchip.com.au Fig.60: a 1904 Baker Runabout at a German motor museum. It had a 560W motor, weighed 290kg and had a 12-cell battery. Source: Michael Barera (CCBY-SA 4.0) Fig.61: the NiMH-powered General Motors EV1. Experimental variants had lead-acid batteries, fuel cells or ran on compressed natural gas (CNG). Source: RightBrainPhotography (Rick Rowen), derivative work: Wikimedia user Mariordo (CC BY-SA 2.0) Fig.62: Tesla’s first car, the Roadster. Source: Alexandre Prévot (CC BY-SA 2.0) Australia's electronics magazine March 2022  45 It was based on a Lotus Elise “glider”, a car body without a powertrain. The battery consisted of 6831 lithium-ion cells in the 18650 form factor. The battery packs had better longevity than expected, retaining 80-85% of their original capacity after 160,000km. Fig.63: this surely must be one of the cheapest EVs available at US$1040 (about $1500). It almost certainly cannot be registered for Australian roads, though. Cheapest electric cars Electric vehicles continue to drop in price, but one of the cheapest is probably the Chinese made Lu Bei LB-6 by Beijing Yezhiquan Technology Co Ltd (see Fig.63). You can buy it from Alibaba (siliconchip.com.au/ link/abbu). It seats four people and has a claimed range of 100-200km from a 30-50kWh lead-acid battery pack and costs US$1040 (about $1500) excluding delivery. It almost certainly cannot be registered on Australian roads. There are many similar ultra-lowcost EVs available from China. You can view a video about driving a similar car to this one by a different manufacturer (Changli) titled “Here’s What The World’s Cheapest Electric Car Is Like To Drive” at https://youtu.be/1GG1RC7GV0Y – that car is not street legal in the USA either. Electric boats Many electric boats of all sizes are now available. Some have solar panels to recharge the batteries. They can also be made in a DIY fashion. Electric race cars Fig.64: typical discharge curves at a constant load current for a rechargeable battery & supercapacitor. Original source: Wikimedia user Elcap (CC BY-SA 1.0) There are several racing series for electric cars of various kinds. Interestingly, all early land speed records, from 1898 and 1899, were held by electric vehicles. The Pikes Peak International Hill Climb record in the USA was set by an electric vehicle in 2018. See the video titled “World Record Run of VW IDR Pikes Peak” at https:// youtu.be/5c2m5hhh5Kw Supercapacitors as a “battery” in a bicycle Fig.65: a supercapacitor-powered electric bike. The supercapacitor bank (blue) stores 11,881J, about the same as one AA cell. The designer also compares a 400F (0.4Wh) supercapacitor to a 21700 size Li-ion cell (14Wh, 45 minutes to charge). 46 Silicon Chip Australia's electronics magazine There are many successful applications of lithium-ion batteries in small vehicles such as bicycles, scooters, skateboards, monowheels etc. We won’t review those here; however, ranges of tens of kilometres are easily possible. In recent years, supercapacitors (and ultracapacitors) have been developed which have incredibly high charge siliconchip.com.au storage compared to standard capacitors (see Figs.64 & 65). We described ultracapacitors in the article “Beyond the capacitor there is the Ultracapacitor” (April 2008; siliconchip.com.au/ Article/1793). These have the advantage of almost instantaneous or extremely fast charging and discharging. However, at the moment, they are not able to replace batteries in high power consumption or high capacity applications. Supercapacitors and ultracapacitors have different discharge characteristics to a battery. A typical battery voltage will remain relatively constant until the end of its discharge cycle, but a supercapacitor will gradually drop to zero voltage as it discharges. Thus, the control electronics have to be designed to power the load over the entire capacitor voltage range (or at least most of it). One YouTuber built a bike powered by supercapacitors to test its usability. See the video titled “Super Capacitor Bike” at https://youtu.be/V_ f8Q2_Q_J0 Fig.66: the Eviation Alice electric aircraft. It has an endurance of three hours and can make about 1000 flights before the battery pack must be replaced. Despite that expense, its long-term projected cost per flight hour is still lower than a turboprop-powered equivalent aircraft. Fig.67: an Australian-made NKD streetlegal electric motorcycle from Fonzarelli (www.fonzmoto. com). The NKDx model has a stated range of 200km, a 12kW motor and a top speed of 100km/h. Fig.68: inside the battery room of an old diesel-electric submarine using leadacid batteries. The technician accesses the batteries via an overhead trolley system. Don’t drop that spanner! Electric aircraft Battery-operated electric aircraft are becoming commercially available. One example is the Eviation Alice from Israel (www.eviation.co), which is now being purchased for courier work by DHL (see Fig.66). It uses a 900kWh battery pack weighing 3460kg. This needs to be replaced after 1000 cycles (about 3000 flight hours) at a cost of US$250,000, which is similar to the cost of an engine overhaul for a liquid fuel powered aircraft of similar capability. The savings seem to be in lower fuel costs and less regular maintenance. The operating cost is about US$200 per hour compared to an estimated US$600-$1000 for equivalent liquid-­ fuelled aircraft. Li-S batteries Soryu class submarine SS-511 SS-512 All-solid-state Lithium-sulfur batteries (Li-S) 230,400kWh Submarine electric motor 8000hp (6000kW) maximum fully submerged speed and time 5 knots: 2094h 87 days 10,470nm (19,390km) 7 knots: 802h 33 days 5614nm (10,397km) 10 knots: 284h 12 days 2841nm (5261km) 15 knots: 90h 20 knots: 39h Electric motorcycles There have been many electric motorcycles produced. Not all of them were commercial successes. A newly developed Australian electric motorcycle is shown in Fig.67. (LiB) 2010 ~ 100Wh/kg 76,800kWh Submarine batteries Since the early days of submarines, batteries have been critical for movement underwater where they cannot run their main engines (see Figs.68 & siliconchip.com.au All-solid-state (Li-S) 2020 ~ 300Wh/kg 230,400kWh (Li-S) 2030 ~ 500Wh/kg 384,000kWh Fig.69: a modern Japanese submarine with proposed future lithium-sulphur batteries. Current versions of this submarine use lithium-ion batteries. Australia was offered the Soryu class submarine as a possible replacement for the Collins Class. Australia's electronics magazine March 2022  47 69). That has changed with the advent of nuclear submarines and, more recently, air-independent propulsion systems or AIPs, although submarines with these power plants would still have batteries. Before the Australian Government wisely decided to purchase nuclear-­ powered submarines, diesel-electric submarines were going to be purchased (although the price and delivery time frame were unrealistic). These could have used either leadacid or lithium-ion batteries; a controversial but conservative decision was made to stick with tried-and-tested lead-acid batteries. For a discussion of why lithium-ion batteries should have been used, see siliconchip.com. au/link/abbv The batteries for the existing Australian Collins Class submarines are made locally and replaced every six years, and will continue to be until 2040. (We contacted the Australian manufacturer for permission to use a photo but they did not respond.) Electric car batteries We described the main battery types used in electric cars last month, but some batteries are being specifically developed for electric vehicles as follows. BYD Co Ltd subsidiary A Chinese company (https://en.byd. com/) has developed a proprietary lithium iron phosphate battery called the Blade battery, which is claimed to use less space than other batteries and be very safe. It has a rectangular form factor. Desten A Hong Kong based company (www. Fig.70: a cross-section of Tesla’s 4680 cell (46mm diameter, 80mm long) along with an exterior image. desten.com), has developed a battery which is said to produce 900kW peak power, have a range of 500km, can be 80% recharged in under 5 minutes and has a 3000 cycle life and 1,500,000km total lifetime range. The battery is expected to be used in the Piëch GT motor vehicle. The battery chemistry and structure is not disclosed. Tesla Tesla first used 18650 cells in their battery packs, then moved to Panasonic 2170 cells and are now migrating to 4680 cells (46mm diameter, 80mm tall – see Fig.70). Tesla believes these cells will halve the cost of the battery packs and increase range by 16%, as they have a much higher energy density than previous cells. 130kWh of these new cells could occupy the same space as 72kWh of the 2170 types. The cells do not use cobalt, a strategic metal. The conductive pathway through the 800mm spiral-wrapped “jellyroll” is reduced due to multiple tabs at the edges of the roll. This is in contrast to a normal jellyroll, where the conductive pathway extends through the entire length of the roll. This is similar to the construction of low-ESR capacitors – Editor Penn State University They have potentially developed a lithium iron phosphate battery (LiFePO4) with a range of 402km in a proposed application that can be recharged in 10 minutes and is good for a 3,200,000km lifetime (see siliconchip.com.au/link/abbw). The battery operates at 60°C. Why use many small cells? Electric vehicles use battery packs made up of a large number of individual cells. There are several good Fig.71: a diagram of part of a Tesla Model S battery module, showing the shape of the coolant passages. The coolant path around individual cells is shown at the left, while on the right, it illustrates how the tubes go through part of the ensemble of cells. There are 7104 18650 cells in the pack in total. 48 Silicon Chip Australia's electronics magazine siliconchip.com.au Fig.72: a drawing of an A cell compared with an actual AA cell. Source: Wikimedia user Lead holder (CC BY-SA 3.0) Fig.73: a B size cell is on the right, compared to a common AA cell. Source: Wikimedia user Lead holder (CC BY-SA 3.0) Fig.74: a 4.5V lantern battery that contains three B cells in series. Source: Wikimedia user Lead holder (CC BY-SA 3.0) reasons for this, rather than using one giant cell (or a few large ones). • In the case of 18650 cells that Teslas initially used, these were already widely optimised for cost and performance, and were readily available as they were used in laptops. • Cooling is much easier to implement with many small cells. A cooling/ heating jacket can easily be wrapped around a stack of small cells. In the case of one large cell, the pipes would have to go through it (see Fig.71). • When many small cells are manufactured, defective or inferior cells can be recycled or used for other, less demanding applications. The best cells can be selected for use in longrange packs. • There is a certain amount of redundancy possible with small batteries. The failure of an individual cell will not destroy the pack. Plus, in theory, individual cells or modules can be replaced, whether by official repair procedures or not. For example, see the video titled “Tesla wanted him to pay $22500 to replace a battery pack, we did it for 75% less!” at https://youtu. be/T7Q0nNkQTCo • A very high density can be achieved with small cells by design optimisation. A large cell might not be so easy to optimise. The ‘wasted’ space between cells is not that large with small cylindrical cells because that space is used for cooling (or heating in winter). • In a pack of small cells, each cell is effectively isolated and can be individually fused. If something goes wrong, only the individual cell and those in series with it will be affected, unlike with a large cell, where everything is affected. This improves safety and reliability. or NiMH rechargeable cells, rather than primary cells. It was also available in fractional sizes (eg, 2/3 length). They were used in old laptop battery packs and radio-controlled vehicles (see Fig.72). The B cell is most commonly found as a group of three in series within the 4.5V rectangular lantern battery, introduced in Europe in 1901 and used in bicycle lanterns until the 1970s (see Figs.73 & 74). They are almost discontinued today. They are not to be confused with the old radio “B” batteries that typically gave 67.5V. siliconchip.com.au More battery information We now look at aspects of batteries and cells that didn’t fit elsewhere in this series. What about A & B size cells? A little mystery of life is why are there no “A” or “B” size cells. Well, it turns out that there are! “A” was a common size for NiCd Internal resistance A cell is not an ideal voltage source where the voltage remains constant The Joule Thief This interesting and simple circuit can drain just about every last drop of energy out of a zinc manganese battery. It is known as the “Joule Thief”. It is essentially a very simple voltage boost circuit that can drive small loads from as little as 0.35V. There are a great many similar designs available online if you want to build one. Only about four components are needed, and according to some designers, these can be salvaged from an old compact fluorescent light (CFL). Australia's electronics magazine A typical “Joule Thief” circuit; it can power the LED until the cell voltage is extremely low, around 0.35V. Source: Wikimedia user Acmefixer (CC BYSA 3.0) March 2022  49 Fig.75: the equivalent circuit of a real battery, showing the ‘ideal’ part with no internal resistance plus the ‘nonideal’ internal resistance. Fig.76: measuring the open-circuit voltage of a cell as part of the process of calculating its internal resistance. Fig.77: measuring the voltage of a cell under load; the reading is lower than in Fig.76 due to the voltage drop across the internal resistance caused by the significant current flow. regardless of the load. In reality, the voltage a battery produces depends on the load due to a property called internal resistance (see Fig.75). This arises from the electrical resistance of the connecting components such as electrodes (eg, carbon rods or metal) and ionic resistance due to aspects of the electrochemical reactions inside the battery such as ionic flow, electrolyte resistance and electrode surface area. The lower the internal resistance, the better. As a battery ages or is discharged, the internal resistance tends to increase. The internal resistance can be calculated by measuring the voltage drop under a known load, but many test parameters affect the value. Internal resistance can be measured using AC impedance methods, provided by a dedicated meter or some battery chargers. AC methods will give a different result to DC methods. Strictly speaking, AC measurements of a battery’s “internal resistance” are actually measuring internal impedance. For batteries, these measurements are typically made at 1kHz. According to Energizer, the internal resistance of a fresh alkaline cell is 150-300mW, depending on size. Other typical values are around 1mW for a car battery or other large lead-acid battery, and for an 18650 Li-ion cell, 30-60mW (AC 1kHz) or 100-130mW (using the DC method). Lead-acid car starting batteries have a very low internal resistance to deliver very high currents for a short period. Note that quoted values for internal resistance vary a fair bit. This same current flows through the internal resistance, so we can reverse Ohm’s Law by saying that the voltage across this resistance is 54mV (1.5V − 1.446V), then since R = V / I, determine that R = 149mW (54mV ÷ 361.5mA). That’s the same answer as using the resistive divider formula. Some other methods of measuring internal resistance or impedance that you can try at home are discussed at siliconchip.com.au/link/abbx Measuring internal resistance Internal resistance (DC) can be measured as follows: 1. Measure the open-circuit voltage of the battery or cell (Fig.76). As there is no external load, this will be the ‘true’ voltage regardless of internal resistance. In this example, we get Voc = 1.500V. 2. Add a load to the cell or battery. In this example, a 4W resistor is used. 3. Measure the new voltage of the battery. In this example (Fig.77), we get Vloaded = 1.446V. The voltage drop is due to the battery’s internal resistance forming a voltage divider with the load. 4. Calculate the internal resistance: Rint = Rload × (Voc ÷ Vloaded − 1). In this case, we get Rint = 4W × (1.5 ÷ 1.446 − 1), ie, Rint = 4W × (1.037344 − 1) which gives Rint = 0.149W or 149mW. For a longer but easier to understand method, calculate the current flow through the load using Ohm’s Law as 1.446V ÷ 4W = 361.5mA. Reproduction batteries for classic cars Some companies produce periodcorrect-looking batteries to provide a perfect authentic look to a restored classic car (see the adjacent photo). Note the external lead bridges connecting adjacent cells. See siliconchip.com.au/link/abca for more details. A reproduction battery for a classic car, in the original style. The internals are modern, however. 50 Silicon Chip Australia's electronics magazine Depth of discharge and battery life Depth of discharge and storage charge can both affect battery life. Panasonic says that their NiMH cells should be recharged when 70-75% of their capacity has been used for maximum service life. A lead-acid car battery should not be discharged more than 50% of rated capacity unless it is a deep-discharge type. Lithium-ion cells benefit by minimising the depth of discharge, avoiding full discharges and charging the battery as often as possible. Many factors affect lithium-ion battery life and these are examined in detail at siliconchip.com.au/link/abby Battery storage It is not necessarily ideal to store batteries fully charged. For example, a lithium-polymer (LiPo) battery rated at 4.2V when fully charged should be stored at around 40% to 50% of battery capacity, a terminal voltage of about 3.6V to 3.8V. One study showed that when a LiPo battery was stored at 40% charge, it only lost 4% of rated storage capacity after one year due to degradation. Another LiPo battery stored at 100% capacity lost 20% of its storage capacity over the same period. Also note that most batteries should not be stored fully drained either. In siliconchip.com.au general, follow the manufacturer’s recommendation for battery storage voltage and temperature. Storage temperature Panasonic recommends storing its NiMH Eneloop cells at 10-25°C, but they should ideally be kept in a refrigerator for maximum life. However, condensation upon removal can be a problem. In general, most cells, such as alkaline types, will have their storage life extended if they are kept in a refrigerator. But don’t put them in a freezer as the electrolyte might freeze and damage the cell. The general principle is that chemical reactions (including those which cause degradation) are slowed down at lower temperatures. Grouping cells When combining multiple individual cells into a battery, such as in a child’s toy or a torch, use matched cells. Cells will age differently in different equipment due to varying current draws or depth of discharge, usage temperature and ageing. If cells are mixed, this can lead to unbalanced cells, and most likely one will go flat before the others, killing the battery prematurely. Low temperatures and lithium-ion cells I was once camping in the snow and found that my camera and phone both stopped working. This is because most common lithium-ion batteries do not work well or at all below about 0°C. This is also a problem with electric vehicles in cold climates. According to the American Automobile Association, temperatures below 4°C reduce the range of typical EVs by 41% or even more if the heater is used. Links for further reading An interesting free book to view online, from 1922, is “The Automobile Storage Battery Its Care and Repair” by O. A. Witte. It’s a fascinating look at the automotive battery technology of that era. See: siliconchip.com.au/link/abc9 Another interesting, short book available online is “General Information and Instructions For the Operation and Care of the EDISON ALKALINE STORAGE BATTERY” from 1925 at www.evdl.org/docs/edison_Fbrochure.pdf There’s also this web page about No.6 dry cells: https://prc68.com/I/No6. shtml Other interesting videos on batteries are: ● “Taking Batteries Apart - Free Carbon Rods & More” at https://youtu.be/ pqmGFfiuXrM ● “Get Lithium Metal From an Energizer Battery” at https://youtu.be/ BliWUHSOalU ● “Don’t Waste Your Money On Batteries – The Shocking Truth I Discovered When Testing RV Batteries” at https://youtu.be/iy3hga_P5YY ● “Shocking Things With 300 9 Volt Batteries!” at https://youtu.be/ ousUTivJoaM ● “Build a DIY Lithium LiFePo4 Headway 12V Battery replacement” at https://youtu.be/5IPnQieycyA ● “Lemon battery breaks Guinness World Record - Royal Institution Christmas Lectures 2016 – BBC Four” at https://youtu.be/6fDail5bvss – they achieved 1275V! ● “This Startup Says Its New Battery Tech Will Beat Every Rival!” at https:// youtu.be/7bgWNQzByOw (Nanograf batteries) short circuit and may also include battery balancing to ensure the individual cells are kept at similar voltages. If you are purchasing a device powered from Li-ion cells such as a torch and you plan to use a protected battery, make sure it will accommodate the several extra millimetres of length taken by the protection circuit. Alternatively, the torch or other device might have its own inbuilt battery protection circuitry. A good discussion on the subject of protection circuits can be found at siliconchip.com.au/link/abbz and more information on batteries and torches in general at siliconchip.com. au/link/abc0 Be wary of cheap chargers Like all extremely cheap items from sites like eBay, be wary of chargers that don’t come from a reputable manufacturer or don’t have good reviews. Some don’t charge according to the correct sequence or termination voltage and can even cause fires. Even with quality chargers, it’s best to avoid unattended charging and to charge batteries (especially lithium-ion types) in a fire-resistant area such as on a concrete or tile floor “Protected” lithium-ion batteries Some lithium batteries are “protected” while others are not. Protection circuits prevent overcharging, overdischarging and damage from short circuits or overload (see Fig.78). You can buy protection circuit boards for 18650 cells and modify or rewrap batteries with them, such as cells salvaged from laptops. There are numerous inexpensive battery management boards available online (eg, from eBay) that protect against overcharge/overdischarge/ siliconchip.com.au Fig.78: the anatomy of a protected 18650 Li-ion cell showing protection circuit, spacers, separators, wrapper and connecting leads. Source: siliconchip.com.au/ link/abbz Australia's electronics magazine March 2022  51 Previous Silicon Chip articles on battery technology Say Goodbye to the 12V Car Battery – July 2000 (siliconchip.com.au/ Article/4313) Fuel Cells – May, June & July 2002 (siliconchip.com.au/Series/226) Get a LiFe with LiFePO4 Cells – June 2013 (siliconchip.com.au/ Article/3816) Tesla’s 7/10kWh Powerwall Battery: A Game Changer? – June 2015 (siliconchip.com.au/Article/8597) Lithium-ion cells – What You Need to Know! – August 2017 (siliconchip. com.au/Article/10763) Grid-scale Energy Storage – April 2020 (siliconchip.com.au/ Article/13801) ● ● ● ● ● ● with no flammable materials close by. Also, never use a charger or other mains-connected device while taking a bath or a spa. Surprises inside some batteries If you open up a 6V lantern battery as used in a “Dolphin” torch, you will typically find four “F” cells or smaller D cells in series. The non-alkaline 6V versions of lantern batteries are a good source of four carbon rods or D cells. Inside a 9V battery, as used in smoke alarms, there are often six 1.5V cylindrical AAAA-like cells in series, although they are 3.5mm shorter (cheaper types contain non-standard ‘pancake’ cells). 9V lithium batteries usually have three 3V lithium metal cells in series. Inside an A23 12V battery as used in some remotes, you will find eight LR932 alkaline button cells in series (see Fig.79) Fake batteries Battery capacities are often massively overrated on websites like eBay and AliExpress, beyond what is physically possible. It’s also quite common for the packaging and branding of a reputable manufacturer to be faked. A real high-quality NiMH AAA cell like the Panasonic Eneloop will have a capacity of 950mAh, while an Eneloop Pro AA cell is rated at 2500mAh. Any ratings significantly above this for NiMH cells indicates that they are almost certainly fake and probably have an actual capacity that’s a fraction of a good quality cell. No genuine 18650 Li-ion cell will exceed 3600mAh. The record is held by the Panasonic NCR18650G, which is no longer available. Typical capacities for good 18650 Li-ion cells are between 2600mAh and 3400mAh. And certainly not 9900mAh as claimed for some cells (Fig.80). These fake cells usually have a capacity well under 1000mAh. Not only do you lose your money, but fake batteries can also leak and destroy your equipment, or in the worst case, can catch fire or explode. Mercury in zinc batteries Standard zinc-carbon batteries such as AA, C and D cells often say Fig.79: inside a 12V A23 battery we find eight 1.5V LR932 cells. Unsurprisingly, 8 x 1.5V = 12V. Source: Wikimedia user Lead holder (CC BY-SA 3.0) Fig.80: a fake 18650 battery. You can tell this from the impossibly high claimed 9900mAh rating. Its capacity was measured (see https://budgetlightforum.com/ node/45556) and found to be 525mAh. 52 Silicon Chip Australia's electronics magazine “mercury-­free” on the label. Why is that? Once, mercury was alloyed with the inside surface of the zinc case to prevent undesired side electrochemical reactions such as hydrogen generation due to the zinc anode’s corrosion, which would lead to battery leakage. Manufacturers changed to a more pure form of zinc to eliminate the problem, and therefore, the addition of neurotoxic mercury is no longer required. Avo multimeter battery Some old AVO multimeters used a 15V BLR121 or B121 battery. These are hard to find and expensive, although they are still made. Many people make up substitute batteries from common and cheaper cells instead. Battery vs chemical fuel Batteries have a much lower energy density than chemical fuels like gasoline (petrol). That is, they contain less energy for a given volume or weight. While gasoline has a much greater energy density than a lithium-ion battery, in a vehicular application, that is somewhat offset by the fact that electric motors are close to 100% efficient compared with modern internal combustion engines, which are about 40% efficient at best. Also, while an electric motor of a given power is generally lighter than a gasoline motor of the same peak power, battery packs don’t get lighter as they are drained, unlike liquid fuel tanks. Vehicle battery packs can be hefty; for example, the 100kWh battery pack in a Tesla Model S weighs 625kg and gives a range of 560-647km. A typical full petrol tank weighs closer to 50-60kg and can provide a similar or better range in similarly-sized vehicles. Exact comparisons between gasoline and batteries are difficult, but gasoline has about 53-129 times more energy per weight than a lithium-ion battery and about 13-37 times more energy per volume. Batteries will not likely ever achieve similar energy densities to chemical fuels because a battery has many components that do not actively store the chemical energy. Electric vehicles can have decent ranges despite this because they are designed to maximise their efficiency (eg, using low-drag shapes, including the wheels). That allows them to make the best use of the available energy and keeps the battery weight reasonable. SC siliconchip.com.au