Embedded legend Jack Ganssle tackles the question of how much juice you can pull from a coin cell. He writes:
About a year ago I wrote of my on-going experiments to determine how coin cells behave. This was motivated by what I consider outrageous claims made by a number of MCU vendors that their processors can run for several decades from a single CR2032 cell. Some vendors take their MCU’s sleep currents and divide those into the battery’s 225 mAh capacity to get these figures. Of course, no battery vendor I’ve found specifies a shelf life longer than a decade (at least one was unable to define “shelf life”) so it’s folly, or worse, to suggest to engineers that their systems can run for far longer than the components they’re based on last.
Conservative design means recognizing that ten years is the max life one can expect from a coin cell. In practice, even that will not be achievable.
There’s also a war raging about which MCUs have the lowest sleep currents. Sleep current is, to a first approximation, irrelevant, as I showed last year.
But how do coin cells really behave in these low-power applications? I’ve been discharging CR2032s with complex loads applied for short periods of time and have acquired millions of data points.
How Much Energy Can You Get From A Coin Cell? - [Link]
Compact battery chargers require overcurrent protection and temperature monitoring to ensure safety. These chargers also need to fit into small form factors, and generally have a lot of pressure to also be very inexpensive, but only have to provide a simple charging ability.
Furthermore, compact packaging is required to integrate the battery charger into a system. Renesas has 8/16-bit microcontrollers available in compact packages with as few as 10 pins, making them ideal for these applications.
78K0/Kx2: 8-bit All Flash microcontroller: wealth of on-chip peripheral functions such as a reset circuit and on-chip oscillator; low power consumption,30 to 80 pins.
78K0/Kx2-L: 8-bit All Flash microcontroller: wealth of on-chip peripheral functions such as a reset circuit, on-chip oscillator, and operational amplifier; ultra-low power consumption, 16 to 48 pins
78K0S/Kx1+: 8-bit All Flash microcontroller: wealth of on-chip peripheral functions such as a reset circuit and on-chip oscillator; 10 to 30 pins
R8C Family: Timer, 5 V operation, and Small Package
P-ch MOSFET: Low on-resistance, compact low-profile
Renesas Battery Charger Solutions - [Link]
The electrolyte is also modified with bio-organic nanodots made from peptide molecules. The new battery technology came about as a result of crossover research into Alzheimer’s disease at Tel Aviv University. The work identified organic peptides (amino acids) which are now being used in StoreDot’s bio-organic battery. The nanodots are made from a range of naturally occurring environmentally-friendly bio-organic raw materials and employ a basic biological mechanism of self-assembly, making them cheap to manufacture.
A conventional micro USB connector would not be able to handle the 180 A necessary for a 30 second recharge of a typical cell phone battery. These sort of charge times would remove a significant hurdle in the development of electric vehicles if the technology is transferable. The design is still at its prototype phase; the developers anticipate the final design of the battery and its charger unit will see a significant reduction in size.
Bio-Battery Recharges in 30 Seconds - [Link]
cpldcpu did a teardown of an external USB battery:
The device has a USB micro-b socket which is used as 5V input for charging, and a normal USB-A socket as 5V output. The output power can be turned off and on by a toggle button. There are LEDs to indicate active power out (blue) and charging (red) states. The pictures above show the innards of the device. Most space is taken up by an ICR18650 LiIon battery, which are relatively common devices with 2600mAH. In addition, there is a tiny tiny PCB. The rear side of the PCB is dominated by a 4.7µH inductor, which is part of the boost converter to convert the 3.7V of the battery to the 5V USB output.
Tear down of a cheap external USB battery - [Link]
Startup company Aquion Energy gave MIT Technology Review a behind-the-scenes look at their battery manufacturing process. The company’s goal is to make non-toxic, cheap batteries for storing off-grid energy. The batteries will first be sold in regions that don’t have access to an electrical grid, such as rural areas and villages in poor countries.
How to Make a Cheap Battery for Storing Solar Power - [Link]
James Wood designed a simple circuit that is able to indicate when the battery of a system is low and needs replacement. He writes:
The Design Idea in Figure 1 indicates a low-battery condition in an audio test instrument that is powered by four AA cells. As the instrument was otherwise an all-discrete design, this same approach seemed more in keeping with the spirit of the project than the use of a single-sourced integrated circuit.
A garden-variety red LED serves as both the indicator and the voltage reference. A small current through R5 forward biases the LED, but its glow at this low value is barely visible, even in a dark room.
Simple circuit indicates a low battery - [Link]
The weak link in electric vehicle technology is the method of energy storage and renewal, making the vehicles impractical for long distance use. The majority of today’s electric vehicles use rechargeable lithium-ion batteries which still have a relatively poor energy density compared to conventional fossil fuels and require lengthy recharge cycles. A promising alternative battery chemistry is the lithium-sulfur battery. It can store as much as four times more energy per mass than lithium-ion batteries.
Unfortunately reactions at the battery’s sulfur-containing cathode form molecules called polysulfides that dissolve into the battery’s electrolyte. The dissolved sulfur eventually develops into a thin film called a solid-state electrolyte interface layer which coats the lithium-containing anode making the battery unusable after only 100 charge/discharge cycles.
Researchers at the US Department of Energy’s Pacific Northwest National Laboratory have succeeded in quadrupling the useful number of charge/discharge cycles. They have developed a graphite shield which moves the sulfur side reactions away from the anode’s lithium surface, preventing it from growing the debilitating interference layer. The new hybrid anode combines graphite from lithium-ion batteries with lithium from conventional lithium-sulfur batteries.
Graphite Boosts Battery Life - [Link]
Xeno Lithium batteries offer high capacity at extremely low self-discharge and are able to supply your device for many years.
Primary Lithium batteries (Lithium thionyl-chloride, LiSOCl2) represent batteries with the highest energy density (Wh/kg), moreover able to operate without problems even in strong frosts. Perhaps their only technical “drawback” is the fact, that they´re only suitable for appliances with low current demands (up to tens of mA). However this “drawback” is already considerably overcome, because with modern components it´s easily possible to design devices with miliWatts power consumption. In principle are the Lithium primary (non-rechargeable) batteries suitable for backup (for example memories) and for power supplying devices with low power consumption, where it´s possible to reach even more than 10 years lifetime. This is naturally a huge benefit, as it enables to construct a device fully independent from external power supply, or without necessity of an external power supply and similar. At the same time it will also eliminate necessity to use an adapter or further electric installation.
These Lithium batteries operate on a principle of reaction Li+SOCl2. Arrising LiCl film on an anode has insulating properties. It provides excellent storage properties and energy preservation, because this passivation layer blocks auto reaction of Li+SOCl2 (self-discharging). Properties of Lithium batteries are also affected by the way and the length of stocking, and it´s possible, that after loading a battery, a short-time voltage drop will occur because of this passivation layer. Maximum capacity usage can be reached at a certain range of discharge currents (according to a diagram at every battery type). If a Lithium battery is intended to supply circuits with a short-time pulse demands, it´s very suitable to use a large capacitor or a supercapacitor connected in parallel with a battery. A capacitor in these cases will supply a bigger energy amount for a fraction of time and from the battery point of view a circuit then appears as one with significantly lower power consumption peaks. This contributes significantly to a maximum capacity usage and it´s also beneficial for a device itself thanks to minimum voltage drop at pulse power consumption.
Nominal voltage of LiSOCl2 batteries is 3,6V and a big advantage is a wide operating temperature range -55 to +85°C (max 150°C). Company Xeno Energy is a producer specializing in Lithium batteries and as one of few in the world they an ISO13485 certification for usage of batteries in medical devices. Further information will provide you the Xeno short form catalogue as well as detailed datasheets of Xeno batteries. In the Xeno production portfolio can also be found special batteries with a higher pulse capacity and type for extra high temperatures -55 to +130°C.
10 years of operation on 1 battery? - [Link]
12V Lead acid battery low voltage indicator, to monitor battery condition during long term storage.
This is a simple circuit that will indicate a low voltage on a 12V lead acid battery. Many that have golf carts, small EV’s, RV’s, or solar power banks for homes have a number of 12V lead acid batteries to maintain and this circuit will help protect your investment while not using these batteries. When stored, batteries will self discharge, and if left for too long, will self-discharge to a damaging level. This circuit will light an LED when the battery voltage decreases to 11.6V. When the LED turns on, charge the battery to prevent the battery from dying on the shelf.
Only a few parts are needed in the small but useful circuit. The BC557 PNP transistor controls the lighting of the LED. The BC557 transistors base is biased by the 10V zener diode. As long as the battery voltage stays above 11.6V, the zener keeps the base of the BC557 transistor high. When the battery becomes discharged, the zener stops conducting and the base bias goes low, and BC557 begins conducting, and the LED alerts you to the low battery voltage. You can use a variable resistor to fine tune the low voltage indication, and/or use a set resistor when you have a good value figured out.
Battery Self Discharge Indicator – [Link]
When observing basic rules will the top quality AGM VRLA batteries last you up to 15 years – we will advise how.
This description could start by a long list of technical improvements of Panasonic batteries. thanks to which they gained a stable place on the top of development in this segment (AGM, expanded positive grid. additives for regeneration from a deep discharge, self-extinguishing container material,…).
However those are things, which can be easily checked up from available internet source or even better from satisfied users. Instead of it, we better bring you a few advices for usage of VRLA/ SLA batteries to serve you as long as possible:
- batteries can be recharged by several ways, but one of the most reliable belongs a „constant voltage/ limited current“ method, i.e. observing max. 2.45V/ cell and a current limitation. It responds 14.7V at 12V battery and a max. current of 0.4CA. This is suitable at so called cycle usage.
- at a stable connection to a voltage source, a voltage per cell shouldn´t exceed 2.3V what is 13.8V at 12V battery. Current limitation should be set to 0.15CA.
- battery lifetime grows significantly with a decreasing temperature, i.e. it is very important to place a battery far from heat sources (transformer,…)
- number of cycles (thus a battery lifetime) is very strongly dependent on a level of discharge before consequent recharging. Dependence is so strong, that for example at discharging to 50% a standard battery will reach a lifetime of approx. 500 cycles, while when discharged in 30% (remains 70% of capacity), the number of cycles will increase up to 1200 (!). The result is, that a choice of a suitable capacity is a key to reach a good lifetime in a given device. Especially in devices, where a battery is daily discharged/ recharged, can a suitable battery (with a higher capacity) significantly prolong a lifetime (thus minimizing costs for replacement).
- if possible, avoid usage of battery on 100% discharge (so called deep discharge). Even though Panasonic batteries manage these statuses and they contain additives for a successful recovery from a deep discharge, but such a usage shortens battery lifetime significantly (to approx. 200 cycles).
- real capacity of a battery (amount of energy, which we´ll get out of it) is strongly dependent on a discharge current. 100% capacity can be reached at a current of 0.05CA/ 20°C. At 0,25CA current it is approx. 75% of capacity and at a current of 1CA it is only approx. 55%. This fact also says for a sufficient sizing of a battery. Especially in applications with a relatively higher power consumption (approx. >0.05CA) we´ll gain by using a 50% bigger battery a resulting battery, with a capacity “increased” in more than 50% (thanks to a relatively lower load of such battery at discharging). Resulting relatively lower discharging current and a lower depth of discharge in every cycle will significantly contribute to a longer lifetime..
- real capacity of a battery also depends on temperature. Difference between a capacity at +20° vs. -10°C is approx. -25%.
- cut-off voltage at which it´s necessary to disconnect the battery is markedly dependent on a discharge current (at a higher current it falls down). That´s why it´s good to set a deep discharge protection in respect to a supposed maximum discharge current.
Above mentioned values apply to standard Panasonic batteries. In the offer of company Panasonic can also be found types with extra long lifetime as well as sa called „Power“ types, suitable for high current devices (UPS,…). On stock we keep a few selected types of Panasonic batteries and upon request, we´re able to provide you any other type. Detailed information about usage and an overview of the Panasonic portfolio can be found in the VRLA Handbook document.
Maintenance-free lead batteries Panasonic will surprise by their lifetime - [Link]