Putting the dots on Li: Is training for lithium batteries necessary?

Series connected batteries

For batteries connected in series, the voltage increases, but the capacity remains the same.

Two 12-volt batteries connected in series are charged with a 24-volt charger

When connected in series, the batteries must be of the same type and age. The capacity and manufacturer must also be the same. If one of the batteries has been used before, then most likely its capacity is already less than nominal and during charging it will be charged first. But the charger may not “notice” this and will try to fully charge the remaining ones. The temperature and pressure in the old battery case will increase. Gas will begin to be released, and the active material of the plates will begin to deteriorate.

Under load, the wear of the old battery will increase. After the weak cells have used up their charge, the good ones will continue to produce current. The voltage across the discharged cells will drop to zero, and then their polarity will reverse (this most often happens in large batteries). An uncontrollable increase in pressure and temperature will follow and a catastrophe will occur.

It is recommended to replace the entire battery of batteries connected in series. If you change only one, the state of charge of all batteries should remain the same. The small difference will be eliminated by the charger during the absorption phase. If the differences are large, the more highly charged battery will be recharged, and the undercharged battery will begin to sulfate.

Two 12-volt batteries connected in series are charged with a 24-volt charger. Three - 36-volt.

Putting the dots on Li: Is training for lithium batteries necessary?

It's been a long time since Ni-Cd and Ni-Mh batteries reigned supreme in mobile devices, but since the beginning of the era of Li-ion and Li-pol, there has been ongoing debate about whether these batteries need to be "trained" immediately after purchase. It’s getting ridiculous, in the ZP100 discussion thread on china-iphone, all newbies were recommended in an orderly tone to go through 10 charge-discharge cycles, and only then come with questions about batteries.

Let's try to figure out whether such a recommendation has the right to life, or whether these are reflexes of the spinal cord (in the absence of the brain, probably) of some individuals who have them left over from the times of nickel batteries. The text can and most likely contains spelling, punctuation, grammatical and other types of errors, including semantic ones. The author will be grateful for information about them (of course, in private, and even better with the help of this wonderful extension), but does not guarantee their elimination.

About terminology

• A
  (Ampere (A), or milliampere -
  mA
  , microampere -
  µA
  ) - the value of the current in the conductor. It can be both big and small. A current of 100A can weld sheets of iron, but if you pick up the wires from a 5V 100A power supply, you won’t feel anything, because no 100A will pass through your skin - the body resistance is too high for the current to pass.
• V
  (Volt (V), or millivolt -
  mV
  , microvolt -
  µV
  ) - voltage value. A high voltage will create a long spark, but with a small current from the source it will only crack you, but will not turn you into a handful of ashes. An example is static electricity, voltage is up to 10 kV, and currents are negligible.
• Ohm
  (Ohm, or kiloohm -
  kOhm
  , megaohm -
  MOhm
  ) - resistance value. It is the high resistance of your body (approximately 15 kOhms) that allows you to hold the wires from the first point. Passing through a wire that has resistance (and all wires have resistance, and the further the wire from the province of China is thinner, the higher it is), the voltage drops by a certain amount, which depends on the strength of the current. Therefore, a thick wire is needed for a heater, and a thin wire for a light bulb, even though the voltage in both cases is 220V. In relation to batteries and batteries (and indeed to all current sources), we can talk about internal resistance. This resistance will not allow you to get a large current in a short time, although the battery very much strives for this during a short circuit - the spark that occurs when the terminals are shorted is just a few amperes of current at a voltage of less than a volt. This is due to the fact that the speed of ions inside the battery is not very high. They're stuck, poor things, knee-deep in polymer.
• W
  (Watt (W), or milliwatt -
  mW
  , then you understood, right?) - in its simplest form, this is direct current power, calculated by multiplying volts by amperes. For example, a laptop power supply that produces 3A at a voltage of 20V, and a laboratory power supply that produces 3V at a current of 20A, will deliver the same power of 60W to the load. They will consume more from the network due to the fact that their efficiency is not 100% - part of the energy will turn into heat.
• Wh
  (Watt-hour) is a measure of energy.
  From the name it should be clear that 1 Wh is the energy that someone will receive (or give) by receiving (or giving) 1 W of power for an hour. Or 60W for a minute. That power supply unit above, it delivers 60 Wh every hour. This is the “correct” capacity, which does not provide information about the battery itself, but gives a complete idea of ​​its capacity. There are also kilowatt-hours, kWh
  - they are written on receipts. If you leave the power supply on, it will consume 60 Wh*24*30 energy in a month, i.e. by approximately 43 kWh, or 73 rubles. Of course, what the power supply produces at the output (those 20V and 3A) must be consumed by someone, and don’t forget about efficiency, I simplified this.
• Ah
  (amp-hours) - Charge. It is generally accepted, although erroneously called capacity. Why is it wrong? Because without voltage, you can’t understand anything from just the 5Ah figure - it only means that, for example, a battery can produce a current of 5 amperes for an hour. Or one amp for 5 hours. But how much energy will be supplied during this hour depends on the supply voltage and the gluttony of the consumer. Simply put, Ah is Wh from which the volts have been torn out (W - V*A, if B is removed, A remains). It would seem that it could be simpler - the battery says 2Ah, 3.7V, multiply 2 by 3.7, get 7.4Wh and rejoice. But there is a nuance(s). Here he is:

  
  This is a graph of the discharge of a lithium battery, which shows that the voltage decreases towards the end of the discharge. This means that simply multiplying Ah by V (which would work in the case of a power supply that produces a stable voltage) gives an energy value with a very large error. In order to find out how many watt-hours there are in a battery, you can, for example, build a power graph (which can be obtained by multiplying the instantaneous current and voltage values) and then find the area under the curve of this graph:

  
  It's more complicated, but the result is watt-hours.

• xC
  is just a convenient designation for the charging or discharging current of the battery. When they talk about charging with a current of 2C, or 0.1C, they usually mean that the current should be (2*battery capacity)/h or (0.1*battery capacity)/h. For example, a battery with a capacity of 720mAh, for which the charging current is 0.5C, must be charged with a current of 0.5*720mAh/h = 360mA

About reading datasheets

A datasheet for the battery was found on Google, consisting of one page:

I'll decipher what is written there. I think everyone understands what Nominal capacity
and
Minimum capacity
- normal capacity and minimum capacity.
The designation 0.2 C means that it reaches such a capacity only if it is discharged with a current of 0.2 of its capacity - 720 * 0.2 = 144 mA. Charding voltage
and
Nominal Voltage
- Charging voltage and operating voltage are also simple and clear.
But the next point is more difficult - Charging. Method: CC/CV
- Means that the first half of the charging process must be maintained at a constant current (it is indicated below, 0.5C standard - i.e. 350mA, and 1C maximum - 700mA).
And after the voltage on the battery reaches 4.2V, you need to set a constant voltage, the same 4.2V. The item below is Standard Discharge
, Discharge. They suggest discharging with a current of 0.5C - 350mA and up to 2C - 1400mA up to a voltage of 3V. Manufacturers are lying - at such currents the capacity will be lower than declared. The maximum discharge current is precisely determined by the internal resistance. But it is necessary to distinguish between the maximum discharge current and the maximum permissible. If the first can be 5A, or even more, then the second is strictly specified - no more than 1.4A. This is due to the fact that at such high discharge currents the battery begins to irreversibly deteriorate. Next comes information about weight and operating temperature: charging from 0 to 45 degrees, discharging from -20 to 60. Storage temperature: from -20 to 45 degrees, usually with a charge of 40% -50%. The lifetime is promised to be at least 300 cycles (full discharge-charge with a current of 1C) at a temperature of 23 degrees. This does not mean that after 300 cycles the battery will turn off and will not turn on again, no. The manufacturer simply guarantees that the battery capacity will not decrease after 300 cycles. And then - how lucky you are, depends on the currents, temperature, operating conditions, batch, position of the moon, and so on.

About charging

The standard method by which all lithium batteries are charged (li-pol, li-ion, lifepo, only the currents and voltages are different) is CC-CV, mentioned above. At the very beginning of the charge, we maintain a constant current. This is usually done by a feedback circuit in the charger - the voltage is automatically selected so that the current passing through the battery is equal to the required one. As soon as this voltage becomes equal to 4.2 volts (for the described battery), it is no longer possible to maintain such a current - the voltage on the battery will increase too much (we remember that the operating voltage of lithium batteries cannot be exceeded), and it can heat up and even explode. But now the battery is not fully charged - usually 60% -80%, and to charge the remaining 40% -20% without explosions, the current must be reduced. The easiest way to do this is to maintain a constant voltage on the battery, and it will take the current it needs. When this current decreases to 30-10 mA, the battery is considered charged. To illustrate all of the above, I colored in Photoshop and prepared a charge graph taken from an experimental battery:

On the left side of the graph, highlighted in blue, we see a constant current of 0.7A while the voltage gradually rises from 3.8V to 4.2V. It can also be seen that during the first half of the charge the battery reaches 70% of its capacity, while during the remaining time it reaches only 30%

About testing technology

The following battery was chosen as a test battery:

An Imax B6 was connected to it (I wrote about it here):

Which downloaded information about charge and discharge to the computer. The graphs were created in LogView. Then I just came up every few hours and alternately switched on the charge and discharge.

About the results

As a result of painstaking work (you yourself try to charge for 2 weeks) two graphs were obtained:

As its name implies, it shows the change in battery capacity over the first 10 cycles. It floats a little, but the fluctuations are about 5% and have no trend. In general, the battery capacity does not change. All points were taken with a discharge current of 1C (0.7A), which corresponds to the active operation of the smartphone. Two of the three points at the end of the graph show how the capacity changes at low battery temperatures. The last one is how the capacitance changes when discharged with a high current. The following graph describes this:

Shows that the greater the discharge current, the less energy can be obtained from the battery.
Although, here's a joke, even at the smallest current of 100 mA, the battery capacity does not correspond to the datasheet. Everyone lies. Although no, a battery test from Mugen Power at 1900mAh for Zopo ZP100 showed quite honest almost-two-amps:

But the Chinese 5000mAh battery only scored 3000:

About the conclusions

1. Training single cell lithium batteries is pointless.
   Not harmful, but wastes battery life cycles. In mobile devices, training cannot even be justified by the operation of the controller - the battery parameters are the same and do not change depending on the model and time. The only thing that an insufficient discharge can affect is the accuracy of the charge indicator readings (but not the operating time), but for this, one complete discharge every six months is enough. Again. If you have a player, phone, walkie-talkie, PDA, tablet, dosimeter, multimeter, watch or any other mobile device that uses a Li-Ion or Li-Pol battery (if it is removable, it will be written on it, if it is not removable - then 99 % is lithium) - “training” longer than one cycle is useless. One cycle is also most likely useless. If you have a battery for controlled models, then the first few cycles must be discharged with low currents (small, hehe. For them, small is 3-5C. This is actually one and a half amperes at 11 volts. And the operating currents there are up to 20C). Well, anyone who uses these batteries knows. But for everyone else, this will not be useful, except for general development.
2. In some cases, when using batteries with multiple banks, a full discharge-charge can increase capacity.
   In laptop batteries, if the manufacturer has skimped on a smart battery controller that doesn't balance the banks in series with each charge, a full cycle can increase capacity for the next couple of cycles. This happens by equalizing the voltage on all banks, which leads to their full charge. Several years ago I came across laptops with such controllers. Now I do not know.
3. Don't trust what's on the labels.
   Especially Chinese. In the previous topic, I provided a link in which a huge test of Chinese batteries did not reveal a single one whose capacity corresponded to the inscription. NONE! They always overestimate. And if they don’t overestimate it, they guarantee the capacity only in greenhouse conditions and when discharging with low current.
4. Keep the battery warm.
   A smart phone in a jeans pocket will work a little longer than in an outer jacket pocket. The difference can be 30%, and even more in winter.
5. Follow me.
   You can do this in my profile (“subscribe” button).

Parallel connected batteries

Parallel connected 12-volt batteries are charged with a 12-volt charger.
When connecting batteries in parallel, the capacity increases, but the voltage does not change. The batteries in the battery should be of the same type and age, and the cables connecting them should be short and thick to reduce voltage drop.

Several 12-volt batteries connected in parallel are charged with a 12-volt charger. The battery charging time will be longer than for a separate battery.

Recommendations for creating rechargeable batteries

• When connected in series and parallel, all batteries must be of the same type, age and from the same manufacturer. The capacity of the batteries when connected in series should be the same; batteries of different capacities can be connected in parallel.
• If, when connected in series, one battery fails, all batteries in the battery must be replaced. If one battery fails when connected in parallel, it is removed and the remaining ones are used until they exhaust their service life. After this, the batteries are replaced.

To avoid premature aging, do not allow batteries to heat up. Every 6 °C increase in temperature above 20 °C reduces the service life by half. Install batteries in well-ventilated, cool areas and leave air space between them to encourage heat dissipation.

• Do not increase battery capacity by using batteries installed in another room. Batteries located in different locations will operate at different ambient temperatures, and their discharge and charging will occur unevenly. This will further increase the temperature difference and lead to premature aging and failure of the battery. If batteries are charged or discharged with high current, thermal runaway and explosion may occur.

  
  Connecting a charger to a battery of parallel connected batteries.

• If batteries are charged or discharged at 200 A at 12 V (100 A at 24 V) for an extended period of time, a significant amount of heat will be generated. To disperse it, use forced ventilation. To do this, install a fireproof fan in the air inlet of the battery compartment. An inlet fan reduces the risk of ignition of hydrogen emitted by the batteries. (Some standards require forced air ventilation any time batteries are connected to a charger with an output power greater than 2 kW, i.e. 167 amps at 12 volts or 83 amps at 24 volts).
• The voltage regulator of any powerful charger must have a temperature sensor that reduces the charging voltage when the batteries heat up
• High-capacity rechargeable batteries with high charge and discharge currents are installed in residential compartments only in sealed containers with ventilation vented to the outside.

Chargers with multiple outputs

To simultaneously charge several batteries from a 220 V network, chargers with two or three outputs are used. If it is necessary to connect a larger number of battery groups, install one of the previously listed decoupling devices.

For example, to charge four batteries, you will need one charger with three outputs and one decoupling relay or charging separator.

Examples of chargers with multiple outputs:

• Ultra Light charger
• 30 Amps
• Charging profiles for Gel, AGM, liquid acid and LiFePO4 batteries. Power supply and half power mode. Login for BMS
• Two outputs Each charger output is capable of carrying maximum current. The total current does not exceed 30 A

ORDER

2 year warranty

• Ultra charger
• 60 Amps
• Marine charger. Efficiency > 90%. Three exits. 12 charging profiles. Gel, AGM, liquid-electrolyte, LiFePO4.
• Temperature sensor included The device reduces the charging voltage if the battery temperature exceeds 20 C

ORDER

5 year warranty

• PS1255 charger
• 10 Amps
• Waterproof charger. Two exits. Current 10 A
• Suitable for one or two independent or series connected batteries Charging current varies from 0 to 10 A per channel

ORDER

2 year warranty

Features of charging in parallel connection

During the start of this process, it is preferable to transmit a fairly large charging current. After all, the surface of the battery will be restored first, and then its lower layers. At the same time, it is desirable to reduce the current, since the intensity of the electrochemical reaction decreases, as a result of which, due to the large amount of energy, the electrolyte may “boil” (its decomposition will occur).

If we consider one of the most popular types of batteries - lead-acid, then if this requirement is violated, it is unlikely to immediately fail. But its service life will obviously be significantly reduced. In general, if we talk about charging power supplies, then it is worth focusing on the fact that it is advisable to use factory devices. If you exploit something else, then certain aspects may not be taken into account (or incorrectly taken into account), which will result in problems in the future.

Selection and installation of equipment

Connection diagram of three battery groups to one charging source.
A battery separator and a DC-DC charger are used, providing four-stage charging of service and additional batteries. If the electrical system consists of starting and service batteries of small capacity, and the charging speed is not critical, use an decoupling relay. For complex systems with multiple subsystems, different operating voltages and powerful charging devices, a battery controller and DC-DC chargers are suitable.

Device rating and cable cross-section

The current consumed by a severely discharged battery reaches 100% of its capacity and, in a large service battery, can exceed the capabilities of the generator. In this case, the charged starting battery will try to equalize its voltage with the service one and will also become a source of current for it. Therefore, the cable and the decoupling devices themselves must be designed for this.

All cables coming from the separation system must be of the same size, cross-section and as short as possible. The same goes for the cables running from the negative terminal of the batteries to the bus and connecting the batteries in the battery. All batteries must be the same type, size, age and discharged equally

Protection devices

The cables coming from the batteries must be protected. To do this, install a fuse or circuit breaker as close as possible to the positive terminal of the battery. Only the cable section from the terminal to the fuse remains unprotected, and the risk of fire from an accidental short circuit is reduced.

An additional safety feature is a main switch that completely disconnects the batteries from the charging source.

Force connection

Separate charging systems separate the starting and service batteries when the engine is not running. But if the starting battery is dead and the engine cannot be started, the batteries must be connected intentionally. Some models of decoupling relays have this capability. However, a large starting current can weld the contacts together and damage the relay. To prevent this from happening, a shunt switch is installed parallel to the decoupling relay and used for emergency engine starting.

Ask a question,

and get advice on outboard electric motors, batteries or chargers for a boat or yacht

Features of battery packing

All three methods of connecting individual power sources into a complex are subject to simple, but important rules for effective and long-term operation.

Series-parallel connection diagram using the example of lithium-ion batteries

Prolonged battery operation and its economic feasibility can be ensured by observing the following rules:

• the electrical capacity of the sources included in the complex should not differ by an amount exceeding 5% of the nominal;
• the operating voltages of individual battery cells must be in a reasonable ratio;
• the operational technical condition of the elements included in the autonomous power supply complex must be as balanced as possible;
• the cross-section of switching lines and buses must be calculated taking into account current loads both inside the battery and in external electrical circuits.

The range of power sources offered by the market, with a competent approach, allows you to create batteries with all the characteristics necessary for reliable use.

Why combine batteries into one unit?

During operation of the systems, ohmic voltage losses are observed. This is the part of the expended energy that is converted into heat without producing useful work. By combining batteries in a certain way, you can reduce losses, increasing efficiency. There are cases when the capacity of one galvanic cell is not enough to operate the equipment. Buying a larger capacity battery is expensive and not always convenient (for example, placement problems). It is more practical to combine two similar chemical energy sources.

Requests for power specifications vary from area to area.

Having identical and similar storage elements, it is easy to satisfy them by connecting sources in different combinations. It's cheaper and more practical.

What's the difference between iPhone and Android batteries?

Battery is one of the areas where iPhone and Android smartphone manufacturers compete. At the same time, representatives of each group think that their counterparts with the battery are doing much worse . Some say that how can you use a 2500 mAh battery when they have 5000 mAh and still don’t have enough, while others talk about optimization and the fact that if you spend it thoughtlessly, then 10000 mAh will not be enough. As usual, both sides are right and wrong at the same time.

How to check battery wear on Android

Examples are given that an iPhone can be used for three years without clearing the cache, while on Android it must be cleared X times a day. In response, accusations fly that Apple saves on everything, including battery capacity (of course, if this can be saved at least a little). Objectively, we can only say that the iPhone is more resistant to damage to the smartphone itself and the battery in its composition (cases of explosion or failure are immeasurably less common), and Android does provide more capacious batteries , but the numbers are deceptive and the devices work for a comparable time.

There is no big difference between an iPhone and an Android smartphone in terms of charging

Smart decoupling devices

Sterling Power Pro Split R Zero Dropout Battery Isolator and Connection Diagram for Charging Three Batteries
Charging relays are constantly being improved. One of the latest models, Sterling Power Pro Split R, has a voltage drop of 0.01 Volts and the following features:

• First of all, it charges the starter battery until its voltage reaches a preset value.
• When the starter battery is charged, it isolates it and brings the voltage on the next battery to the same value. Returns to charging the starter battery if it detects that its voltage has decreased.
• Repeats this process for all connected batteries.
• After all the batteries are charged to the same voltage, connect them all in parallel.
• If the voltage on any battery drops, for example due to a high-power load connected, Pro Split R isolates all batteries and charges only the one whose voltage has dropped.
• To accurately determine the moment of switching, it controls the rate of change of voltage, and does not simply trigger when a certain threshold is reached.
• The 180 A model allows overcurrent up to 2000 A

How to properly connect two batteries?

To successfully carry out this operation, you should follow the following tips:

1. It is necessary that both the first and second batteries are in perfect condition. As you know, rechargeable batteries, after a certain number of charge and discharge cycles, begin to deteriorate, become unusable, and, as a result, discharge faster. If you connect an old battery to a new battery, the old battery will “absorb” energy from the new one, and eventually both batteries will be discharged. This, in turn, will not allow the power unit to start.
2. A switch should be used for the second battery. This device will use the energy of the first battery, but will allow you to retain the charge of the second charging capacity. This will also allow you to always remain confident that you can calmly “sit down and leave.”
3. In order to avoid damaging the vehicle's electrical wiring, it is worth using a more powerful generator, or installing another one.
4. The batteries should be approximately the same power, but if the batteries are of different power, this can lead to failure of the batteries.
5. It is necessary to use short cords to connect the batteries, then the operation of these batteries will be most efficient.

So, by trying to follow these recommendations, you can make your leisure time in nature, fishing, hiking or hunting truly colorful and unforgettable.

However, you need to decide on how to connect the two batteries to each other.

The first method: serial connection: a jumper is placed over the terminals: its own jumper for the “negative”, its own jumper for the “positive”, then the remaining two “opposite” terminals of the two batteries are connected to each other, and the “positive” and “negative” wires are connected to the rest of the vehicle's electrical system.

Second method: parallel connection: with this type of connection of two batteries, the jumper is placed as follows: the “negative” and “positive” terminals of the batteries are connected, then wires are removed from the paired batteries, which are connected to the rest of the vehicle’s electrical system.

After the batteries have been connected to each other, you should install either a switch or a switch between them.

This step will allow you to use the energy resource of only one battery. For example, when the engine is turned off, the car lights or audio system will work.

If the vehicle's engine is turned on, the energy required to operate electrical appliances in the car is generated by a special generator. But, the truth is, fuel in a vehicle is wasted much more, and this, in turn, leads to incredible fuel costs.

Conclusion

Summarizing the above, it is worth saying that installing a peripheral battery in a car will be the best solution. Now you don’t have to worry about sudden battery discharge and subsequent problems getting a spark for ignition.

But the second battery will only be effective if it has been installed and connected to the first in accordance with generally accepted recommendations and standards. Incorrectly connected batteries will become a real headache for the car enthusiast. When choosing a battery, you need to focus not only on the size, capacity and brand, but also clearly understand the purpose of the battery and its scope of application. For example, there are starter and traction batteries designed for different purposes.