How to repair a lithium-ion battery

Lithium-ion batteries are probably one of the most popular consumables in the world. They are used everywhere from portable electronics to electric cars. Unfortunately, the cells in any battery are subject to degradation whether the battery is in service or not. Sometimes the battery fails much earlier than its potential end of life.

When a battery shows no signs of life and there is no way to replace it now, users often wonder how to rebuild a lithium-ion battery. In fact, it is possible, but only if the cause of the malfunction does not lie in the active components.

Consider situations where it makes sense to try to save a lithium-ion or polymer battery, and when. not.

Charging different types of batteries

There are several types of batteries installed in screwdrivers. nickel-metal hydride, nickel-cadmium and lithium-ion. Each has unique features, and charging is done according to the recommendations for that species.


The most popular type of battery, its advantages are compact size, low cost and high capacity. Can withstand over a thousand recharging cycles, depending on the quality of the materials used in their manufacture, as well as compliance with the conditions of use.

This type of batteries has a significant disadvantage. the memory effect. If you interrupt their charging before the end, the capacity of the battery will decrease over time. In addition, their production is very toxic, so some European countries have refused to use them.

Nickel-metal hydride

These batteries represent a new generation of technology of the previous type, their production and operation is almost completely safe for the environment. They have a much smaller memory effect. They have the major disadvantage that they have a high self-discharge current. Batteries of this type are stored fully charged, and if they are not used for 30 days, it is recommended that their capacity be restored.


Batteries of this type are considered the best. Charge quickly, have no memory effect. These batteries do not need to be fully discharged, and it is allowed to connect them to power as needed. The disadvantages include high cost, as well as a fear of low temperatures.

Li-ion batteries of an electric screwdriver should be properly charged at a temperature of 10 to 40 ° C, and if they become hot during this process, they should be cooled to prevent breakage.

Can’t charge the battery

An electric screwdriver sometimes fails after prolonged use. Its operating element can no longer be charged, making it impossible for the tool to perform its functional capabilities, the tool will “die” in rough terms.

In order to extend the life of the tool so you don’t have to take it out of range, you can try three methods in turn. Each subsequent one is considered more complex and costly. They consist of:

  • restoring and increasing the capacity after a reversible loss of capacity (memory effect);
  • Adding distilled water to the electrolyte;
  • Replacement of some or all of the battery units.

BMS board

BMS (Battery Management System). a battery management system. BMS board is extremely important when converting an electric screwdriver to lithium. Why you need it and how it works? It controls the charge and discharge, preventing the electric screwdriver battery from overdischarging and overcharging, and it has a built-in “balancer” that charges each Li-Ion battery separately in the assembly. The latter is extremely important! There are BMSs without a balancer! 3S. 12v, 4s. 14v, 5s. 18v To choose a BMS board, you must consider that the minimum current must be 30A, otherwise it will go into protection.

The BMS board option at the link is 2-3 more expensive than some basic versions, but you get 100A instead of 30A or 40A. In my opinion, in terms of functionality is the best BMC board from aliexpress and deserves this token overpayment.

Instructions for setting up the charger

Everything is according to the crude description)). Works perfectly. I will use it to charge a converted electric screwdriver. Arrived in Samara in 25 days. For those who can’t figure out how the LEDs work, I found a great description:

The upper one is on as long as the inverter is able to supply the load with the set current (in the case of using it as a charger it turns out to be a CC phase indicator, as soon as it goes out. The middle LED lights up until the current in the load goes to 0.1 set, extinguished. charging is over.

0 value.1 is set by default, if you want it can be adjusted either more (charging faster, less capacity) or less (charging time increases, the battery is charged more fully) with the middle potentiometer. But the charge continues even after it is switched off, this is only an indication that the battery is in principle charged and ready for use. Lower LED. just a converter performance indicator.

charge. this LED is illuminated as long as the current in the output circuit is above the preset value. This value is set in relation to the maximum current. When setting a large maximum current (units of amperes) it may not be possible to set the indication to a small current (units and tens of milliamperes).

Possible causes of the “death” of a lithium-ion battery

Li-Ion batteries gradually lose their ability to hold a charge during use. A high number of charge-discharge cycles and prolonged exposure to elevated temperatures cause abnormalities in the movement of the lithium ions and further damage the battery. Also the reason that the Li-Ion battery does not charge can be a problem of corroded current conductors. The metal, damaged by corrosion, is unable to move the electrons properly.

Corrosion in batteries is usually caused by the interaction of the electrodes with the electrolyte. Graphite reacts with the electrolyte from the very first charge. As a result of this interaction, a porous layer is formed that protects the anode from subsequent influences. It is effective in normal temperature conditions, but at higher temperatures and excessive discharging of the accumulator, it partially dissolves in the electrolyte. When normal conditions resume, a new protective layer is created, but this process consumes lithium. As a result, the battery has to be charged more and more often.

If the layer protecting the graphite anode gets very thick, it prevents the free movement of the lithium ions. The result is a decrease in capacity. Therefore it is very important when using lithium-ion batteries to avoid critical discharge and extreme temperatures. If you neglect these requirements, you can soon wonder why the lithium-ion battery does not recharge?

Ten battery features to compare. Which is better?

Each type of battery has its own advantages and disadvantages, and to determine which type of battery is best for an electric screwdriver, you can only compare them by features and characteristics. I have selected the 10 most important factors to give you a full comparison of all battery types. As a result you have the possibility to choose the battery that best suits your purpose, your applications and the conditions in which you use your electric screwdriver.

How many charge-discharge cycles the battery can withstand. Determines how long it will last. The longest-lasting batteries. nickel-cadmium.

  • Electric screwdriver with nickel-cadmium battery. 1000 cycles. Often this number is not a limit and the equipment is still able to work, charge and discharge for a while.
  • An electric screwdriver with a Li-Ion battery. 600 cycles.
  • The nickel-metal hydride batteries that screwdrivers are equipped with are 2-3 times inferior, their index is 300 cycles, the highest quality devices. 500 cycles.

If you have a lot of work to do, a lot of screwing and unscrewing, then li-ion or ni-cd batteries are the battery of choice. They charge very quickly.

  • charge time for lithium ion batteries (depending on capacity). half an hour to 2 hours. It is very convenient to take two of these batteries to replace. While you work with one battery, the second battery charges.
  • Charging time of nickel batteries for screwdrivers. 4 to 8 hours. Again, it all depends on how big the battery is.

Undoubtedly, lithium-ion, because they are the most high-tech. Rechargeable lithium-ion type battery. This is the lion’s share of the price of an electric screwdriver, not less than half its cost. The cheapest batteries. NiCd. NiMH batteries are slightly more expensive, but compared to lithium-ion batteries. They are very inexpensive, and replacing a dead battery is simple and inexpensive.

If you are planning to drive screws into hard materials or to tighten long, thick fasteners, the electric screwdriver must be used with high loads and at full power. The battery has to be able to withstand that kind of treatment in order not to shut it down. In this case the nickel storage batteries (NiCd or NiMH) are relevant. They are immune to power gain. But lithium-ion batteries are weak in this regard, they are better to buy for home. for domestic work, where there are not strong power loads.

Negative “memory effect”. Who has it stronger

The memory effect. is a very unpleasant and widespread problem. This is because the battery “remembers” the residual capacity where you started charging it. If you had, for example, 20% left, and you put the battery to charge, it will “remember” this number as zero. Then, when working, when it reaches 20%, the drive will show you that the charge is gone and you need to recharge. This is very inconvenient. To avoid this problem you should always make sure the discharge is down to zero. But what can you do if you still have 20% to 30% of the charge and you have a lot of work to do the next day?? Then you’d better choose a lithium-ion battery. It has no memory effect at all. There is a reason it is so expensive. You can recharge it whenever you want or when you need it. With nickel batteries this Focus does not work, they just “remember” the level of the previous residual charge.

If you charge an electric screwdriver, use it for a while, and then hide it in a drawer, it will run out after a while. So the next time it’s ready to go, it’s not going to be ready to go. You have to charge it again. This is called self discharge. It appears differently with different types of batteries. Here we see again why lithium-ion batteries are considered the most advanced and so expensive. They have negligible self-discharge, only 1.6% for a month without operation. That’s with proper storage (25 degrees warm and 100% full charge). If the temperature is lower, it can lose up to 3%, but no more. Just to compare. Nickel batteries have a self-discharge rate of 10 percent for a month out of service. That is, a charge of 60 percent, disappears in six months. And lithium-ion screwdrivers, with this residual charge, will be ready to use even after a year of storage.

The battery is located in the handle of the tool. The lighter and more compact it is, the more convenient it is to work with an electric screwdriver.

  • The lightest and smallest. Lithium-ion. They are placed directly inside the handle.
  • NiCd and NiMH batteries. heavy and massive. Brought outdoors. Holding an electric screwdriver by its weight, over your head, makes the tool very heavy and makes your hands tired.

those who only work with an electric screwdriver indoors can skip this point. And here’s one for those craftsmen who have outside work planned, outdoors. it is very important how the battery reacts to frost. Here’s where our beloved lithium-ion batteries lose a lot to nickel batteries. The Li-Ion battery is designed to work in the temperature range from.20 to 60. But in fact, in the cold quickly loses capacity. And nickel storage batteries also work at sub-zero temperatures, below.20.

Zero discharge. Who can take it better?

  • Nickel batteries not only tolerate this temperature well, even the opposite. you have to work so that the tool is completely discharged.
  • Lithium ion batteries are best recharged at 15-20% charge. They don’t like full discharges.

Service life depends in part on the number of charge-discharge cycles. But in many respects it is also determined by the design of the battery itself, by the interaction of the electrodes with the electrolyte. In general, although lithium-ion batteries have 600 charge-discharge cycles, and nickel-cadmium. 1000, lithium batteries have a much longer life. I will therefore reassure those who do not understand why they paid so much money for an electric screwdriver with a lithium ion battery. I explain: for durability, absence of “effect” of memory and absolutely negligible self-discharge.

How to handle, store, where to dispose of leftovers

Because of the above, lithium-ion batteries should be handled with caution. Danger of fire and explosion arises from incorrect charging, short circuits and mechanical damage. The latter is especially true for lithium polymer batteries, which do not have a rugged protective casing. Accidentally or intentionally piercing or tearing the film protecting the battery, you can already in 10-15 seconds get in your hands a blinding red flame. It can also happen when bending or squeezing the battery, and particularly if you pierce it with a tool. This can occur when trying to remove the battery glued with double-sided adhesive tape from the cell phone in order to replace it with a new one. The risk is lessened by removing a discharged battery and this should be done before you start working. For the same reason, and the fact that when shorted it can give dozens if not hundreds of amps of current, such batteries should be stored safely and carefully packed, not in a pile of junk.

In general, these batteries should be brought to a 30-50% charge level before storage. They should be stored at room temperature. Some “experts” say they should be kept in the refrigerator. You do not need to. But old, dead and especially bloated batteries must not be stored under any circumstances, you must get rid of them as soon as possible, as they are unpredictable and can at any time cause a fire.

The question of “where to dispose of” is complicated enough. Given the environmental hazard of lithium (on the MAC is close to lead), they must be disposed of by special organizations, but in our country I do not know such organizations working with private individuals. Do not throw them in the trash and especially not in battery containers. Perhaps the ideal solution is.- Some kind of sealed box with sand in the open air, the contents of which would be picked up by special services.

You can’t (and if you really want to, you can’t either!) trying to solder the batteries. Spot welding only! The exception.- Lithium polymer ones with specially lengthened solder pins and cylindrical batteries with pre-welded ribbon blades. Even slight overheating can lead to depressurization followed by self-ignition, melting of the separator and internal short circuit.

All sorts of shamanism like “push the battery” or “unlock the controller”.- is the risk of having a fireball in your hand,. or bed. Remember, if your battery controller locks up, it’s not because a money-grubbing manufacturer wants you to buy a new one. That’s because the manufacturer doesn’t want to pay for damage caused by batteries catching fire.

Assembling a battery charger (whatever.- as an independent product or as part of any design), it is necessary to carry out the first charging cycle by connecting a voltmeter and milliammeter together with the battery, and making sure that it works correctly. And pay attention to the measurement accuracy: the maximum allowable deviation from the nominal voltage of 4.2 V does not exceed 1.2%, and the error of common inexpensive multimeters with 3.5 digits when measuring this voltage to the limit of 20 V reaches 1%.

Assembling a battery of several batteries, you must select the closest (within 1-3%) to the capacity of the cells in series connection, and the internal resistance.- in parallel. Before connecting the cells in parallel, equalize their voltages. Cells for the battery must be strictly of the same batch.

Do not repair a battery by replacing one cell with a new one. Unbalancing is almost guaranteed. And you already know the danger of unbalance (hint.- fire and explosion).

Fuse.- This is what should be in the circuit of any lithium-ion battery.

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