Rate this article:
Somehow recently it became necessary to measure the capacity of one battery in a smartphone, since it began to discharge too quickly, and, of course, I wanted to order another little thing on AliExpress. As a result, after spending a couple of minutes searching, we found it on AliExpress, for sure, but Aliexpress had another promotion and the price turned out to be more profitable. If you decide to buy, check it yourself, maybe the situation will change at that time, but don’t forget that, so don’t be lazy and calculate for yourself where it will be more profitable for you to make a purchase. But let's not deviate from the topic and return to the actual review of the device itself.
Fortunately, we were able to find a device for measuring battery capacity from, which has already sold more than two thousand of these testers and has only positive customer reviews about the product. If you search for it yourself, here is the original name of this tester “for your reference”; perhaps a better offer will come up at the time of your purchase. At the time of ordering, the price of the tester for measuring the battery capacity was $4.26, since we were on some kind of promotion, the regular price was $7.10, but we managed to buy it even cheaper, thanks to the cashback service on Aliexpress. Ultimately, we paid $3.90, delivery was indicated, the order was placed, all we had to do was wait.
As a result, after about 20 days, the parcel arrived. By the way, the track code was without letters, just digital and was tracked only until the moment of export from China, after which all that was left was to wait, fortunately the parcel arrived quickly, but small items usually always arrive faster than large parcels, so nothing surprising. The seller packed the device for measuring battery capacity in a standard yellow international envelope, having previously wrapped it in several layers of bubble wrap, for which special thanks to him. Inside the envelope, everything turned out to be exactly as indicated in the description of the product. On the back of our device for measuring battery capacity there is information about the permissible input and output voltage and the maximum capacity level of the indicator. This information is mainly for lovers of experiments who love playing with sockets, but since we bought it for simple household needs, such as measuring the battery capacity of a smartphone, tablet, camera, we simply took this information into account and decided to check the performance of the tester.
First of all, we connected the tester to the tester using a USB cable, which is built into the case on one side, and on the other we inserted a USB cable from the phone. Immediately all the necessary information appeared on the screen, about voltage, current strength, and a counter started working, indicating the amount of charge transferred, which is measured by mAh ( milliamp hours). Actually, the device for measuring battery capacity already performs its main function and copes with it quite well. But if you look closely, you will notice a small button next to the display. It is needed for comparative measurements, in other words, this memory of 10 cells in which the indicators of your measurements are saved. This function works according to the following principle - with short presses of the button you can scroll through the readings of saved measurements, you can activate the viewing of cells with one double press, and reset with one long press. As for us, the function itself is not particularly necessary, but perhaps it will be useful to someone.
We tested a device for measuring battery capacity on both smartphones, tablets, and (Original Xiaomi Power Bank 16000mAh), which we recently ordered from. Of the declared 16000mAh, in an almost new external charger we were able to count 15874, which is very good. We also connected it to, the results were also pleasing, after 3 months of use, the battery capacity decreased by only 2%, however, the original Xiaomi products have not caused any complaints for a long time.
If you want to accurately measure the volume of your battery, we recommend connecting the battery capacity measuring device to a completely discharged device, and only then charging it.
Of course, you can’t expect extremely accurate readings from a device for a couple of dollars, but it’s a necessary thing in everyday life, especially for all sorts of geeks who love to do all sorts of experiments. Definitely, the functions of this tester are more than enough to measure the battery capacity of your smartphones and tablets.
(function(w, d, n, s, t) ( w[n] = w[n] || ; w[n].push(function() ( Ya.Context.AdvManager.render(( blockId: "R-A -184100-2", renderTo: "yandex_rtb_R-A-184100-2", horizontalAlign: false, async: true )); )); t = d.getElementsByTagName("script"); s = d.createElement("script "); s.type = "text/javascript"; s.src = "//an.yandex.ru/system/context.js"; s.async = true; t.parentNode.insertBefore(s, t); ))(this, this.document, "yandexContextAsyncCallbacks");
I’m sharing my idea of the easiest way to measure battery capacity without buying expensive measuring instruments. The test sample was a 18650 lithium-ion battery, but my method of measuring capacity will work for other batteries as well.
The first part of the article describes the budget option.
In the second - (without a multimeter and USB tester).
At the end of the article there is a small one.
Modern electronic devices widely use lithium-ion (Li-Ion) batteries of various shapes and sizes.
Regardless of the standard size, they all have similar characteristics and, by and large, differ only in capacity.
As a rule, there are batteries with a nominal voltage of 3.7 Volts (although there are also 3.8 Volts).
3.7 V Li-Ion batteries cannot be charged above a voltage of 4.23 V and cannot be discharged below 2.5 V, otherwise an irreversible process will occur and the cell will only have to be thrown away. The battery can be discharged and charged to any value (it does not have a memory effect), as long as the voltage is in the range from 2.5 to 4.23 V. However, a completely discharged battery should be charged as soon as possible so that it does not lose its capacity prematurely.
Also, lithium-ion batteries differ from each other in the presence of protection. The battery may have no electronic protection (just a galvanic cell), or it may have a built-in circuit that protects the cell from over-discharge, overcharging and overheating.
But no matter how you protect and monitor the condition of the battery, its capacity will steadily decrease over time. The higher the operating temperature and the more charge-discharge cycles are performed, the faster the battery ages.
18650 is the designation of the most common Li-Ion battery, the dimensions of which are slightly larger than a regular AA battery (18x65 mm). Everything that applies to the 18650 battery also applies to other lithium-ion batteries!
The 18650 battery size is often used in high-power flashlights, lasers, and various electronics. Batteries for laptops, some screwdrivers, and even electric vehicles are assembled from 18650 cells.
If you buy a branded battery, it most likely has built-in electronic protection. Cheap Chinese batteries, ordered for example from Aliexpress, do not have protection. In addition, their capacity is usually several times lower than declared.
The capacity of lithium-ion batteries is usually expressed in milliamp-hours (mAh). If your 18650 cell has an inscription like “1800” or “2200” on it, this is its declared capacity. It is more correct to measure capacity in Watt hours, but when marking elements, only milliamp hours are indicated.
To measure battery capacity, charging and other research, there are many special devices in a wide price range. The most famous of them, IMAX, costs about 2,000 rubles. Such a purchase will be justified only if you charge different types of batteries every day.
What was it all about? My laptop battery began to drain very quickly. Typically, a battery consists of 6 18650 cells. If even one cell fails, it affects the performance of the battery as a whole. Therefore, I decided to find out which of the elements had decreased in capacity in order to replace it with a new one. Cells from a laptop battery, as well as most budget 18650 batteries, do not have individual protection, so when working with them, they should not be over-discharged or overcharged.
Operating procedure
A few photos and a short review of the USB tester at the end of the article
Circuit diagram of a homemade USB tester, measuring the capacity of a Li-ion 18650 battery I intended to find out the battery capacity using the method described above, but the USB tester that arrived from China 2 months later turned out to be faulty, so I decided to measure the capacity without measuring instruments.
Luckily I already had a Powerbank. Its design is such that, on the one hand, it prevents the battery from being discharged below the permissible voltage, and on the other, it maintains a constant 5 Volts at its output. If we connect a 5 Ohm resistor to the 5 Volt output, we get a discharge current of 1 ampere. And this value should theoretically be maintained throughout the entire discharge time. The current (1 A) and voltage (5 V) are known, all that remains is to note the time. In order not to sit for an hour with a timer in your hand, you should connect a regular household electromechanical alarm clock (clock) to the Powerbank output in parallel with a five-ohm resistor. But the clock requires 1.5 volts (the voltage of a AA battery), and we have as many as 5. Therefore, we connect the clock through a voltage divider consisting of two resistors - 470 and 1070 Ohms. If you have a multimeter, you can use a 470 Ohm - 1.5 kOhm variable resistor instead of these resistors, setting the clock input to 1.5-1.8 Volts.
So, I set the hands to 12:00 and connect the ballast with the clock to the Powerbank. After some time, the battery will discharge to 2.5 Volts. The power bank turns off, the clock stops and the hands record the time. In my case, the discharge time was 50 minutes (50 min/60= 0.83 hours).
Now let's calculate the battery capacity.
If we wanted to calculate the capacity of the Powerbank as an independent device, we would simply multiply the current and time: 1A*0.83h=0.83 Ah or 830 milliamp-hours.
But we need to know battery capacity 18650, so you should multiply the result by the ratio of the Powerbank voltage (U.pwb) to the rated voltage of the 18650 cell (U.b). In addition, for a more accurate result, we divide everything by the efficiency of the Powerbank converter, which is approximately 0.95.
In view of the above, the final formula for calculating battery capacity will take the form:
I * t * U.pwb / U.battery / efficiency = 1A * 0.83h * 5V / 3.7V / 0.95 = 1.18 Ah (1180 milliamp-hour)
The experiment revealed the occurrence of pulsations that interfere with the operation of the clock. Therefore, a capacitor had to be soldered parallel to their input (in place of the battery). The capacitance at which the circuit operates stably is 100 microfarads (more is possible), the capacitor voltage is any, but not less than 5 volts.
During the discharge, the 5 Ohm ballast resistor heats up above 100 degrees, so do not grab it. Solder the circuit so that this resistor does not touch the Powerbank body or capacitor, otherwise they will melt.
If you want the discharge to go faster, use 2 5 Ohm resistors soldered in parallel, in this case the current will double and the discharge time will be halved. The video demonstrates in accelerated mode the operation of a watch with a stepper motor, which also turned out to be Chinese and periodically jammed when lying down. For further experiments, I connected a Soviet clock with a pendulum mechanism, which works absolutely stably.
For convenience, you can calculate the price of dividing the dial in accordance with your scheme and mark the scale in American hours and/or in Watt hours. In this case, the clock will always have a ready result and additional calculations will never be needed.
So, a brief review of the USB tester purchased in China through the Aliexpress website - everything that we managed to film before it failed.
After receiving and unpacking, I decided to check the performance of the tester. To do this, I connected it between the charger and the smartphone. You can see that the device shows voltage, current, current power consumption, operating time and energy consumed (Watt-hour). To measure the battery capacity, just connect the USB tester between the battery and the load resistor; after the battery is completely discharged, the USB tester will turn off and the measured capacity will be stored in its memory. However, the matter did not go further than theory, because the tester turned out to be defective. When connecting a load of 5 Ohms, which corresponds to 1 ampere, the device stopped displaying current and other parameters to be measured, although the declared permissible load current is 3 Amps. At the end of the video, the operation of a mouse connected to a laptop via a USB tester is demonstrated. Here the tester is already in a faulty state. Previously, the mouse current he measured was from 10 to 30 milliamps for the resting and active states, respectively, but now the current is not displayed.
USB tester disassembled: 
This time - an intelligent charger for Ni-Mh batteries of AAA and AA sizes.
Why intellectual?
Unlike conventional chargers, which are sold cheaply by the Chinese or are included in kits such as “10 cheap batteries and a cheap charger for 2000 rubles”, and are charged in a “drip” way, this charger has a controller, which contains programs for fast charging batteries , and some other features - like determining capacity and “training” batteries to restore capacity.
99% of batteries sold in stores are AA or AAA form factors - Ni-MH. This is due to qualities that are more attractive to consumers - less noticeable memory effect, large capacity. True, along with these characteristics, the kit also comes with fast self-discharge (when, after some time, unused batteries have to be charged again).
LSD Ni-MH- Ni-MH with low self-discharge. Despite the intriguing abbreviation in the name, it is just an abbreviation for Low Self-Discharge :) Despite this, they have several more advantages - higher discharge currents, the ability to work at low temperatures, and an increased number of operating cycles.
More terms for those who have not read the article about charging lithium batteries.
Medium current charging with temperature control.
In this mode, the battery is charged with currents from 1/3C to 1/2C, which allows charging in an acceptable time - from 5 hours. When charging with such currents, the battery begins to heat up after the end of the charge, which can lead to its explosion. Therefore, in such chargers there is a temperature sensor next to the battery, which monitors a sharp increase in temperature and stops the charge. If charging is even a little “smarter”, it first discharges the battery to get rid of the memory effect, and then starts charging it. Some models also count the time from the start of charging, which allows you to indirectly judge the health of the battery - if charging ends in a much shorter time (an hour or an hour and a half), then the battery is faulty, which is indicated by charging.
High current charging with -ΔV and temperature control
The fastest charging technology. The battery charges at high currents (1C to 2C), allowing the battery to be charged in an hour or two. 
The basic principle of this technology is that before the end of the charge the voltage always increases, and immediately after a full charge it decreases. Not by much, by tens or even a few millivolts. The controller in the charger constantly monitors the voltage on the battery and, after a voltage jump down, reduces the charging current to approximately 10mA - to compensate for self-discharge - so that the batteries are always ready, even if they are left charging for a day.
There is a danger of not noticing this point, and seriously overheating the battery at such currents, so all chargers additionally have built-in temperature protection - thermal sensors for each battery, which temporarily turn off the charging process if the battery gets very hot.
As a rule, manufacturers do not limit themselves only to this mode - if you build in a controller, then you can add several more functions to it - current control, to determine the actual battery capacity, a training function - when the battery is charged and discharged several times to compensate for the memory effect, and others functions.
Using the Mode button you can select the operating mode - Charge, Discharge, Test, Refresh. To select, you need to hold the button for 2 seconds, after which you can select the mode with single presses. The first mode is Charge. It is installed by default and simply charges the batteries to full capacity. The second is Discharge, discharges and then charges the battery. The third one charges the battery if it was not charged, then discharges it, measuring the capacity in the process, then charges it again. Recovery - the fourth mode, cyclically discharges and charges the batteries until the capacity stops changing. 
As I understand it, the point of use is this - if you need to charge the batteries quickly, then you just need to insert them and select the charge current. And if time is of the essence - for example, if the batteries are useful only in the morning, then it is better to select the discharge or test mode - the batteries will be discharged, and then automatically fully charged. Thus, both the wolves are fed and the sheep are safe - the batteries will be charged without your intervention, and the discharge-charge scenario will eliminate the memory effect.
The testing mode takes longer because to determine the capacity, you must first fully charge the batteries. But after its completion, you will receive information about the battery capacity, and if something happens, you will be able to replace a suddenly dead battery in time (this is better than finding out about it during operation).
I talked about the main functions, everything else is in the manual: 
You can view all photos, including those not included in the review, in original resolution in the Picasa album. There you can ask a question or leave a comment.
If you do not have an account on Habrahabr, you can read and comment on our articles on BoxOverview.com
Only registered users can participate in the survey. Come in, please.
If you are going to buy batteries, but you do not yet have a charger, or you want to buy a charger to replace the old one, then the question inevitably arises - which charger to buy, what to choose from the huge variety?
Why do you need a quality charger?
The service life of high-quality NiMH batteries with proper care is on average 3-5 years. The capacity of modern batteries is comparable to the capacity of expensive alkaline (Alkaline) disposable batteries, but unlike them, batteries can be used from 500 to 3000 times. The benefits of buying batteries are obvious!
In order for batteries to last a long time and work efficiently, it is necessary to choose the right charger. A common mistake many buyers make is buying expensive high-quality batteries and buying a cheap charger or using an old one they bought a long time ago. As a result, even the most expensive batteries will quickly fail.
There are at least 3 reasons why you shouldn't skimp on a charger:
1. Cheap chargers can charge batteries extremely slowly - up to several days;
2. Also, cheap chargers can charge batteries very quickly, but at the same time they may not have proper protection against overheating and overcharging of batteries, which significantly reduces their service life.
3. Cheap chargers do not allow you to control the charging process and may not have automatic shutdown after the battery has finished charging. You have to calculate the charging time “by eye”, this is not convenient and not accurate - the batteries can either be undercharged or overcharged;
All these factors negatively affect the quality of the batteries and also significantly reduce their service life.
Problems can be prevented or solved with a quality charger. Manufacturers offer a variety of chargers aimed at a wide range of consumers: from advanced users who want complete control of the battery charging process and parameters, to ordinary buyers who do not want to know anything about the battery charging process.
What should you consider when choosing a charger?
When choosing a charger, pay attention to the following important points:
1. Availability of independent channels for charging each battery separately
Many cheap chargers only charge batteries in pairs. This creates a number of inconveniences in use. Firstly, you need to ensure that the pairs of batteries used in devices are not confused. Secondly, many devices use an odd number of batteries, which cannot be charged in such a charger. You have to look for some kind of additional battery to supplement the pair for charging, which is very inconvenient.
In addition, over time, the batteries in a pair begin to differ in capacity, which affects the duration and quality of operation of the pair. The difference in capacity can reach such an extent that, due to one undercharged battery, the pair practically stops working and it becomes impossible to use the batteries.
for AA/AAA+CROWN
for Li-ION+AA/AAA:
XTAR MC2 XTAR MC2S
TrastFire TR-001
4. Availability of the “discharge” function
The “discharge” function is a very useful function that allows you to extend the life of batteries and maintain high performance. The fact is that batteries are considered discharged when the voltage on them is 0.9 Volts, while many electronic devices turn off when the voltage on the battery drops only to 1.1 Volts or higher. When charging a battery that is not completely discharged, the “memory effect” appears over time, which consists of a loss of battery capacity and a decrease in its operating time.
To prevent the “memory effect”, it is recommended to completely discharge the battery before charging it. You can drain the battery using a flashlight or a child's motorized toy, but doing so runs the risk of over-discharging the battery. If the battery voltage drops below 0.9V, smart chargers may perceive it as faulty and not charge it.
Therefore, to discharge batteries, it is recommended to use chargers with the “Discharge” function.
When using batteries in toys or flashlights, do not allow the batteries to become deeply discharged. If you see that the battery is already low (the flashlight is dim, the motor in the toy is spinning weakly, or the sound is distorted), replace the batteries.
5. Availability of additional functions and features
Currently, the most popular are smart chargers that allow you to independently set battery charge and discharge currents, accelerate battery capacity, measure and restore battery capacity.
Buying such a charger makes sense if you constantly use batteries and you need to be confident in the capacity and performance of the batteries, or if you just like to experiment and explore. Also, such a charger is an excellent gift for anyone who uses batteries.
Smart chargers:
Separately, it is worth noting the smart chargers of the device, which are equipped with various additional accessories: AA and AAA batteries, travel bags, adapters. The quality of complete batteries and accessories is usually quite high, and the cost of batteries included is usually lower than the cost of similar batteries separately. Therefore, purchasing chargers with accessory kits can be very profitable.
Smart chargers with accessory kits:
Among the smart chargers, advanced chargers can be distinguished. These chargers are distinguished by the presence of additional functions and capabilities: screen backlight, measurement of internal battery resistance, a wide range of charge and discharge current settings, manual setting of the number of charge/discharge cycles for training/overclocking.
Advanced chargers:
6. Ability to work with batteries of different formats and sizes
If you use batteries of different types (Ni-MH, Li-ion) and different sizes, in order not to buy a separate charger for each type of battery, you can purchase a universal charger that is suitable for charging several types of batteries. Universal chargers are no worse than separate chargers for each type of battery. In terms of functionality, they can also be simple, which simply charge batteries, or advanced, which can charge, discharge, test and train batteries, and measure their capacity. Universal chargers combine the ability to work with Ni-MH batteries of sizes AA, AAA, C and Li-Ion batteries of sizes 18650, 14500, 16340, 26650, 20700, 21700, etc.
Universal chargers:
7. Ability to work with a large number of batteries
There are situations when it is necessary to charge many batteries at once - 6 -12 or more. It is quite obvious that using the most common chargers for 4 batteries in this case is inconvenient; the charging process takes a lot of time and requires additional attention. Using multiple chargers can also be an inconvenient solution to the problem.JBC-017
8. Super-fast chargers.
More and more Li-ION batteries with high load capacity are appearing on sale for electronic cigarettes, power tools, and powerful flashlights. In most cases, such batteries can be charged quickly without affecting their service life. For these purposes, special chargers are produced that allow the use of maximum charge currents for Li-ION batteries:MiBoxer C2-4000
(the paragraph below is intended only for Ni-MH batteries; modern Li-ION batteries can be charged by fast devices with currents of up to 4 amperes.)
Currently, you can find many chargers on the market that are called super-fast, ultra-fast, etc. This means that they are able to charge batteries quickly. What does this mean in practice? This means that chargers use high currents to charge batteries - 1000 mah per channel and above. Without temperature control of the batteries and cooling system, high charging currents cause the batteries to overheat, which has an extremely negative impact on their life expectancy. A high-quality super-fast charger must have a good cooling system, thermal sensors for monitoring battery temperature, and an overheating protection system. Otherwise, the lifespan of the batteries may be reduced by several times that stated by the manufacturer.
Special fast chargers with temperature and battery charge level control:
As a summary, we can say that to charge high-quality batteries, it is advisable to purchase a high-quality charger that will ensure a long battery life and high performance. Choose the optimal charger, which in its functionality will allow you to work with your batteries at the level you need. Before purchasing, it is also advisable to consider whether additional functions may be useful to you in the future, even if you do not intend to use them now.
Thank you online store
http://batterex.com.ua/ for the materials provided
Battery-powered personal devices can range from a single battery cell, such as mobile phones, to several, such as electric vehicles. Anxious anticipation of an impending battery discharge (in English this is called range anxiety) is typical for working with all autonomous electronic devices. Users worry about whether they can get through a movie before their tablet battery dies, or whether they can drive their electric car to the next charging station without getting stuck in the middle of the highway. The charge sensing system is the component responsible for determining the remaining energy in the battery. This article describes a charge sensing system used in single cell devices. Various algorithms for determining battery capacity used in such systems are considered, as well as the pros and cons of these algorithms. The article also touches on some of the factors that need to be considered when selecting a charge sensing system for consumer battery-powered applications.
Figure 1 shows a block diagram of a standard charge meter. It consists of at least two ADCs, one of which is designed to measure battery current. The second ADC is multiplexed and can be used to measure battery voltage and temperature or serve as a general purpose ADC. The measured voltage, current and temperature are fed to a microprocessor, which implements a charge determination algorithm. The microprocessor's non-volatile memory contains certain information about specific battery characteristics, such as impedance or cell capacity versus voltage. A built-in or external regulator provides the microprocessor, ADC and other circuits with regulated supply voltage. The charge meter communicates with the rest of the system using standard protocols, such as I 2 C.
The simplest algorithm for assessing charge is to determine the battery capacity from the voltage measured on it using the graphs in Figure 2. Figure 2 shows the standard dependence of the voltage of a lithium-ion battery on its capacity. From the graph you can obtain the capacitance value at a given voltage. Figure 2 also shows how capacity decreases with increasing number of charge-discharge cycles. The method based on voltage measurement is easy to implement and allows you to find out the exact value of the maximum battery capacity (Q MAX) when there is no load on it. However, the actual usable battery capacity (Q USABLE) is less than the maximum capacity due to the battery's internal impedance (Figure 3). The average battery impedance (R BAT) can be used to estimate usable capacity, but this estimate is likely to have large errors because R BAT is a function of the battery's temperature (T), age (Age), and state of charge (SoC). Although, in principle, a large multivariate table can be used to adjust the battery resistance, calculating the resistance requires a lot of information about the battery and the circuit.
A more advanced solution is the charge counting method. In this case, the charge flowing into and out of the battery is integrated to obtain an accurate estimate of the current capacity. This method works well provided that the initial charge state is precisely known. If the original capacity of the battery is known, integrating the total current can obtain the current capacity. The main problem with this method is that it does not take into account the self-discharge of the battery, since the self-discharge current does not flow through the external circuit. This may lead to inaccurate capacity estimates. Self-discharge can be modeled, but all models are imprecise, and the level of self-discharge depends on the temperature and age of the battery.
To overcome the problems of both methods, battery voltage and current information as well as battery temperature can be used to predict capacity. In this case, the open circuit voltage is measured when the battery is not loaded, and the current measurement is performed while the battery is charging or discharging. The battery voltage is measured continuously, even when there is no load. Continuous voltage measurement is used to update the current state of charge based on the graph shown in Figure 2.
Then, when a load is applied, the resulting charge flowing into or out of the system is determined by counting. After removing the load, the battery is given some time to recover, and the voltage is measured again. Using the data from two voltage measurements and the results of calculating the total charge, you can determine the maximum battery capacity. It is also possible to calculate the current impedance based on the measured current, the open circuit voltage adjusted for temperature and state of charge obtained from the lookup table, and the voltage measured under load. Thus, knowing the maximum capacity and impedance value of the battery, you can get an accurate estimate of the remaining usable capacity.
Choosing a chip for measuring charge
When choosing a charge detection microcircuit, the main attention should be paid to the accuracy of the algorithm, current consumption and the number of external components necessary for its normal operation, primarily voltage regulators and current-sensing resistors. Even when the actual load is disconnected, the IC remains on to periodically measure the open circuit voltage. Any energy used by the charge meter will reduce system runtime, so the chip must have low quiescent current. It requires a regulated power supply for the ADC, microprocessor and other blocks, as well as a low-impedance resistor to measure battery current. Ideally, all of this would be integrated on a single chip to reduce the number of external components and save board space. An example of such a meter is a microcircuit containing an LDO regulator.
Factors considered at the system level are where the meter is installed (battery side or host side), its initialization, and algorithm design. When installed on the battery side, the meter is placed directly on it. This allows it to be in sync with the battery at all times and provide instant information about it. If installed on the host side, the meter must be properly initialized each time the battery is installed. When installed on a battery, the algorithm is developed by the battery manufacturer, so the system integrator simply needs to request a battery that meets the required parameters. The only downside to this method is that the chip will be thrown away along with the battery when it becomes unusable, potentially increasing the overall cost of the system. When placed on the host side, the system integrator must have experience in charge measurement and the time required to develop the algorithm must be factored into the work schedule.
Conclusion
Estimating battery capacity is a complex task because capacity is affected by many interrelated parameters. Simple algorithms can lead to inaccurate results, which can potentially reduce system runtime. Therefore, when designing charge sensing devices, trade-offs must be considered at both the chip and system levels.
