MAX1555. USB Charger for Li-Po Battery

Publikovano 23.06.2012

The battery is a lithium-ion - the thing is not new and many of the ways to charge it. I will describe a practical example of a charm of a single-bounte (3.7V) Li-Po. battery using food USBconnector. Charging USB - this is the most convenient way for mobile devices and appliances.

But before describing the scheme charger, Consider the batteries themselves. Exist simple batteries, sort of such:

And batteries with a built-in charge controller. A controller is performed as a tiny board soldered to the battery conclusions. Please note that such batteries usually have contacts in the form of wires.

Indeed - this is logical: to supply the battery controller charge. Let slightly more expensive, but how much less hassle. But what lies under this title: "Charge controller"?

This is just a battery protection chip from overvoltage, excessive discharge and short circuit. The essence of its actions is simple - with extended voltages or current, the chip turns off the transistor key, disconnecting the battery from the chain. Sometimes there is a voltage of 0V at the output of such a battery. Do not be scared, it does not mean that the battery "died." Just the battery was discharged to the lower limit and the charge controller turned off it. It is enough to charge it.

How to charge such batteries? Answer: just like Li-Po. Battery without charge controller. Li-Po. Battery with charge controller is just a battery with additional protection. What battery is better - choose to you. But you must remember that Li-Po. The battery is afraid of excessive charge and excessive discharge. And if the problem with an excessive charge is solved by the charger, the probability of discharge the battery below the permissible limit is forced to apply Li-Po. Battery with charge controller.

Thus, we decided that both options Li-Po. Accumulators - and with charge controller and without it - require a special charger. What will happen if Li-Po. Battery stupid to stick to 5V power USB? You will be surprised, but the battery charges! Although the process of charging is not called normal, and with such charging the battery will not live for a long time. Moreover Li-Po. Battery with charge controller with full charge will turn off (protection will work). Although by this time the battery is pretty pretty, nothing terrible, may not happen. But without charge controller, the battery can end up life in a bright flash, and burn your computer, or where you get it there, along with the house / office / factory.

There is a cheap "Chinese" way to charge Li-Po. Battery (but only with charge controller!) Through a current-limiting resistor. And parallel to the resistor include the LED. The LED goes out with full charge. Those. When protecting protection. This method is used in children's Chinese toys, when moving / flying / floating toy is charged from the battery of the remote control unit. This method is suitable if your uncle works on the battery factory, and you have these batteries "well, they just went out" (c). We also reject it, although ... no: still reject. We are not Chinese and uncle on the rechargeable factory we have no! And we love the users of our devices, so, charge Li-Po. Battery We will be correct.

Simple battery llipo charging scheme:

For this we take a special chip and turn it on as indicated in. Please note that the microcircuit has two inputs - USB (3.7-6V) and DC (3.7-7V) To connect the DC power supply. Those. At least straightened.

I made a small test scarf for. The LED glows while the charge goes and goes well when charging the battery is completed. If the battery is not connected, the LED does not burn.

As a result, we have a miniature charger for Li-Po. batteries. Such a scheme can be built on the fee of your device and charge it from USB. In combination with Li-Po. Battery with charge controller Get a complete protection device Li-Po. Battery and correct charger. Long years of service Li-Po.!

One of the most important criteria for the correct work, good efficiency and long service life of the battery is considered its correct charge. This applies to all batteries all the batteries, be it massive industrial rather big capacity, or tiny batteries in your tablets or phones.

Most of the batteries have the so-called "memory effect" in one extent. It is expressed in the fact that the batteries "remember" the limits of the operated capacity.
For this reason, in fact, the preparatory training of batteries is carried out. Due to the presence of the above result, it is not recommended to charge not yet sitting until the end of the battery.
In this case, rechargeable batteries among other things "will remember" the limits to which they are given the opportunity to reach.
The result will be the reduction of the physical capacity of the batteries, their rapid discharge, the diligence of the service.

When purchasing new batteries, it is recommended to produce their "training". It consists in full discharge / charge the batteries itself. Speaking easier, it is necessary to discharge batteries, then charge them "until the stop". The process is repeated 3-4 times.
Subsequently, the battery procedure will serve significantly longer. With all this, you seem to "accelerate" them, increase the potential container to the limits.

The less time the battery is discharged and the less deep is each separately taken its discharge, the longer the service life will be.

How can I charge the battery?

• The optimal version is charging with a constant current 0.1 - 0.2 C for 6-8 hours.

• Fast charge - for 3-5 hours. The current is about a third of the nominal.

• The accelerated charge is performed by a current equal to the value of the nominal capacity of the battery itself, it is possible to warm up and the destruction of the item.

Such batteries are used in your phones, tablets, laptops.
Standardly received a shock that their voltage is 3.7 volts, but one element may have a voltage in the range of 2.5 (discharged) - 4.2volt and this is usually maximum.
On average, their resource 1000 - 1500 cycles charge-discharge
As a rule, if the battery is discharged below 2.5 volts or charge more than 4.2 volts - the battery fails. To protect from this in most of the batteries of this type there is a security board that turns off the battery bank when the voltage output beyond the norm.
A charging device should be able to charge batteries up to 4.2 volts and automatically disable charge.

A newer variety of lithium-ion batteries with greater energy density and a smaller size (element thickness from 1mm! With significant flexibility). Use up to minus 20 degrees. And the complete absence of a "memory effect".
The batteries of this type are swing and fire-dangerous, when recharging, fast discharge or closing the element. Therefore, all elements are equipped with a built-in charge controller and discharge board.
The number of working cycles in a wound 900 full charge-discharges. It should be noted that a deep discharge can completely remove the battery. It is recommended to discharge such batteries for no more than 40% of their maximum container.
Charging is made by voltage 4.2 volts per element, current in 1C and the charging process is completed at a current 0.1-0.2c. Charge time is about 2 hours.

Often your performance as ordinary finger batteries. The supply voltage of one element is 1.25 volts.
Service life, approximately 200-500 cycles charge-discharge. Self-discharge: 100% per year.
In a minor degree, the battery owns the "memory effect", it means that if the battery is for a long time, the month - two, it was not used, then it's nada to make a full cycle of discharge - charge.
The charge with a small current extends the battery life, so the most optimal mode of operation will be charged current at 0.1 from the nominal battery capacity.
Charge time - 15-16 hours, according to manual instructions.
The charge of such batteries is better to do with a constant or impulse current with very short pulses of the negative value (asymmetric current) - this will help to eliminate the problems with the "memory effect"
The charge voltage on the element is 1.4 - 1.6 volts, and the voltage of the fully charged element is 1.4 volts. Discharge to produce up to 0.9 volts, below it is undesirable.

Most produced in the form of finger batteries and small-sized disk batteries (pills)
Power voltage of one element - 1.37 volts
This type of self-discharge is about 10% per month.
They are subject to the "memory effect" and such batteries are not recommended to be used in buffer mode. After a long inactivity of such a battery, you need to produce a circuit-discharge cycle of approximately the nominal container. The discharge cycle with 1.36 volts to 1 volt is not recommended below.
Rated charging current in the range of 0.1-1 from the nominal container of the element.
It can be used at temperatures up to minus 50 degrees.

PB (lead-acid) battery

The most common type of battery energy.
Most safe method Charging looks like this, first the battery is charged with a constant current, and after receiving the desired voltage, this voltage is maintained on the battery.
Maximum value charging Tok. 0.2 - 0.3 from the nominal battery capacity. The optimal charge current is 10% of the nominal, it is safe and is punitive for the battery.
The maximum charge voltage should not exceed 13.8 volts. For rapid charge It is allowed to 14.5 volts.
The total time of the total charge must be in a rayan 5 - 6 hours.
The minimum charge temperature is not lower than -15 ° C

AGM battery

In contrast to lead-acid, they contain absorbed electrolyte, and not liquid as in acidic, edible glass tissue gaskets between lead plates are impregnated with electrolyte. And this gives them a number of advantages: resistance to large vibrations, confident operation, even with minus 30 s Although the voltage slightly seats, hermetic design and more secure charging.
The number of full charge-discharge cycles from 500 to 1000 depending on the model brand.

Over-compact charging for lithium batteries as 1s (3.7V / 4.2B) and 2s (7.4 / 8.4B) - first of all, for all sorts of photo-video techniques and different lanterns that do not have their own built-in "carcass" Charging (as well as for charging additional batteries). The range of input voltages 5-18B (required so that at the input voltage is at least 1B higher than the voltage on the charging battery).

Charge current:

• for 3.7V - 0.75A
• for 7.4B - 1A

These charge currents are optimally universal (and most importantly, safe !!!) for the overwhelming majority of batteries of any photo-video cameras.

To assess the dimensions in the photo is a ruble coin :)

Waterproof performance. Protection against short circuit and crooked polarity (really works - I checked it yourself! :)

For "subjects" to battery contacts, customizable clamping contacts from the "Ketai frog" are used. There is an opportunity (with difficulty "subject" due to the battery design), change places plus and minus the contacts "Frog".

Well, naturally, there are always options to connect to the accumulator contacts "Alternatively", for example, by fixing the conductors using an elastic band or isol :)

For batteries with "very hit-up" contacts (and this, as a rule, Sony batteries) additionally attached the wiring detachable in order to slightly "upgrade" the original charger - to fall this connector to the output contacts of the original charging.

Switching between 3.7V and 7.4B is made by opening or closing the wiring (see photo). The condition is closed - 7.4V, open - 3.7V (this information is also "drawn" on the board, for forgetful :)

The output connector from the board (which is to the battery) is made by me compatible with the whole family of universal type charges imax (Dad connector of type Deans. , he is T-plug. ) - i.e. can be used at home (and in the car) imax (With the same "frog" and other contacts), and in purely hiking - for lightness and compactness, just take this scarf instead of Imax, the size of a little more ruble coin :)

Important note:

This charge charge has one feature (this is rather a "bug", but "Fich" - but you need to take into account) - she has a very slow the final part of the charging (CV - Constant Voltage). Roughly speaking, about 98% of the battery capacity charging is perfectly simply (within the framework of the indicated currents), but the final "impetitive" - \u200b\u200bsooooo slowly! Those. From the moment when the battery is already charged, and before the lighting of the LED indicator, signaling about the end of the charge, can take a very long time!

And in some cases (basically, it concerns the batteries of 7.4V from the photo-video), it is possible and not to wait for the lighting of the LED - as, for example, in the battery of my pentakovskaya mirror ... The fact is that in its battery there is a balancing board, "Balancing "Voltage up to 8.3V - while charging fee is waiting for an estimate of 8.4V :) And in the end, it does not wait for it ... :)

How to deal with it? Yes very easy!

First, you can simply estimate the charging time (and the charging current is known to us, the battery capacity is also written on it). For example, I charge the battery with a voltage of 7.4B (7.2V or 8.4B designations - it's all the same :) and a capacity of 1600mAh. Accordingly, with a charge current about 1a, the battery can be considered after an hour and a half.

Secondly, you can simply touch the throtsel on the charge charge (this is such a large square-round item on the board, the largest of all the details :) if it is warm to the touch, then active charging continues. But if its temperature differs little from the total temperature of the entire board (it is clearly not felt by the finger), it means that the active charging is over, and you can safely disconnect the battery.

Here the main thing is to remember the simple truth: a small underwear for lithium-ion batteries is not only not harmful, but everything is exactly the opposite, it is very useful to increase their service life !!! So do not be afraid of lithium batteries for no fear, we wonder only reloading (fortunately, this charging board does not allow this :)

The first company, who launched into mass production, the rechargeable lithium-ion battery of a large capacity became Sony, while the battery life has become much longer than it had nickel-cadmium analogue.

Unfortunately, in the first models there was a significant disadvantage, which was manifested by the fact that at high current discharge, the lithium anode flamped.

It took about 20 years to eliminate this problem, the solution was the controller, which does not allow to form a pure lithium on the anode of a lithium-ion type batteries.

Modern models are reliable and safe, they gradually crowded with nickel-metal hydride and nickel-cadmium nickel rechargeable batteries In portable devices, they are installed as a power source of a laptop, a camera, a mobile phone, etc.

The only niche in which lithium-ion type batteries are inferior to nickel-cadmium - these are devices whose work requires a high discharge current, for example, for screwdrivers. This type of batteries is called industrial.

Separately, it is worth mentioning the elements of Li-Pol. The only difference from the lithium polymer battery lies in the fact that another electrolyte is used in the base basis, while the principle of operation, the features and characteristics of these species are almost identical.

Features

Any type of power supply has its advantages and, respectively, disadvantages, lithium ion batteries Only confirm this axiom. Consider in detail their characteristic features.

The merits, undoubtedly, include:

• low speculation parameters;
• if you take a single element of the lithium-ion battery, the dimensions of which are equal to the batteries of another type, then it will be more charge (3.7V, in contrast to 1.2V). Due to this, it became possible to significantly simplify and facilitate the battery;
• there is no such parameter as a power memory, that is, the battery does not require regular discharge to restore power (capacity), which simplifies operation.

Speaking about the advantages that this accumulator element has, it is impossible not to take into account certain flawsTo which include:

• built-in "fuse", that is, the protection board, the task of which limit the supply voltage when charging and not allow full discharge The battery, in addition to this, smoothes the maximum current, and also controls the temperature. Because of this, the price of lithium-ion batteries is higher than that of the analogues;
• despite the restoration of lithium-ion type batteries, they are exposed to "aging", even if they store them in accordance with the rules of operation. About how to slow down this process will be discussed below, where the operation and its features will be considered.

Video: Overview, Opening of a lithium-ion battery from a mobile phone

Form factor

Lithium ion batteries are available in two form factors - cylindrical and tablet.

Many devices use several connected lithium-type batteries, for example, to reach voltage 12V or increase the discharge current, it must be considered if you want to buy a similar device (as a rule, the connection type is indicated on the housing).

How to charge

There are rules, thanks to which you can significantly extend the service life of lithium-ion type batteries.

The rule is the first: it is impossible to allow complete discharge, due to this you can increase the number of cycles in which charging and discharge occurs. Charged battery by 20%, it is possible to significantly extend its life, at least twice. As an example, we give the table of the dependence of the recharge cycles, depending on the depth of the battery discharge.

The rule is the second: with a frequency once every three months, it is required to produce a full cycle (that is, completely discharge and charge), due to this the process of "aging" of the batteries is slowed down significantly.

Rule Third: You cannot store a lithium-ion type battery fully discharged, it is desirable that the battery is charged by 30-50%, otherwise the restoration of its capacitance is not possible.

Rule Fourth: To charge the battery, use the original charger, which came complete from the manufacturer, this requires the difference in the battery protective circuit. That is, for example, batteries HTC, EN-EL, Sanyo, IRC, ICR, LIR, MAH, Pocket, ID-Security, etc. It is necessary to charge the Samsung battery device.

Rule fifth: You can not allow the battery overheating, the lithium-ionic device can be operated at ambient air temperature ranging from -40 to 50 ° C. With violated temperature mode It is not possible to restore the battery or produce it, it will be necessary only to replace it.

Separately, it must be emphasized that rechargeable batteries famous brands Significantly superior to the specifications of analogs of unknown manufacturers. You may not doubt that DMW-BCG batteries, VPG-BPS, SAFT, as well as original models, such as BL-5C, BP-4L (Nokia), D-Li8, NB-10L (Canon), NP-BG1 (Sony ) Or LP243454-PCB-LD will definitely better than Chinese analogues.

Homemade charger

If you wish, you can make your own hands a device that will serve to charge lithium-ion type batteries, its scheme is shown below.

Designations in Figure:

• R1- 22;
• R2 - 5,1K;
• R3- 2;
• R4 -11;
• R5 - 1kom;
• RV1 - 22kom;
• R7 - 1kom;
• U1 is the LM317T stabilizer (be sure to install on a radiator with a large area of \u200b\u200bscattering);
• U2 - TL431 (voltage regulator);
• D1, D2 - LEDs, you can use SMD type, first, signing about the start of the charging process, it is desirable to choose red, second - green;
• transistor Q1 - BC557;
• capacitors C1, C2 - 100N.

The input voltage on the lithium-ion type battery charging scheme should be from 9 to 20V, a pulse power supply can be removed for this purpose. The power of the resistors must be selected the following:

• R1 - minimum 2W;
• R5 - 1W.
• the remaining is not less than 0.1255W.

as a variable resistor RV1, it is desirable to take CG5-2 or its imported analogue of 3296W. This type allows you to more accurately set output voltage, which should be about 4.2.

The principle for which the charging scheme is following:

When you turn on the battery is enabled, the current value depends on the resistor R5 (in our case it will be at the level of 100mA) the charging voltage ranging from 4.15 to 4.2V, the diode diode will be promoted on the start of the process. When the battery approaches the charging threshold, the load current will be reduced, which will turn off the D1 LED and turn on D2.

Note that when a voltage is reduced by about 0.05-0.1V, you can significantly increase the life of the battery, since it will not be charged to the end.

Contacts for charging block through which the battery will be connected, you can take from a broken device, do not forget to clean them before.

It is necessary to note that with incorrect adjustment, for example, an overestimated voltage or charging current, you can output the battery.

The production of the charger costs much cheaper than the price of a lithium-ion battery, whether it is a city of Moscow or St. Petersburg, so save (considering how the selling them is developed), risking with the battery, using the homemade device, does not make sense.