How to Know When an Electric Screwdriver Battery is Charged?

Some models have an indicator light that will indicate when the unit is fully charged. Immediately disconnect the battery from the power supply after charging. Usually takes anywhere from half an hour to 7 hours to charge, depending on the battery and charger. NiCd batteries take the longest to recharge. 3 to 7 hours.

  • If a battery is being charged for the first time, it must be fully discharged before it can be used, and then fully recharged.
  • The temperature in the room should be between 10° to 40°.
  • To prevent the unit from overheating, it is necessary to disconnect the battery pack (battery) from the charger as soon as it is charged.

How an electric screwdriver battery works

The battery is a device designed as source of direct current, which is transmitted from the batteries. When charging a rechargeable battery, energy is stored in the system on the contrary.

The structure of the acb in electrical appliances has the same elements:

Energy is stored and transmitted by connecting the batteries in series with each other. A characteristic feature of the “banks”: the same size and voltage of the individual cells.

When the battery of an electric screwdriver fails, usually only one or more batteries fail.

In addition to batteries, battery performance is affected by damaged contacts. Powerful ones allow the device to draw power and release it. The temperature sensor protects the electric screwdriver from overheating. And the service wire equalizes the charges in all cells.

In addition, the operation of the device is influenced by the type of battery.

How long is the optimal amount of time to charge?

Generally, the time required to fully charge a battery is given in the instruction manual for the screwdriver. We recommend that you follow these guidelines. There are often indicators on the charger to let you know when the procedure is complete and when it is over. They will help you determine how long to keep the battery charged. Remove the battery from the charger when it is done, so as not to damage it.

The battery of an electric screwdriver normally takes from half an hour to 7 hours to charge. For example, a 1.2Ah nickel-cadmium battery will take about 7 hours to fully charge at 250mA.

There are two types of battery chargers, regular and pulse chargers. The first ones are designed for household screwdrivers and charge a battery in 3-7 hours. The latter are used in professional equipment and can restore the capacity within 1 hour.

What to do if the battery is not charging

If there is no battery charge, there may be the following reasons:

  • Charger malfunction.
  • No contact between the battery and the charger.
  • Faulty safety sensor.
  • Residual capacity is very low.
  • Failure of individual cells in a battery pack.

Charger malfunction can be checked with a voltmeter or other battery.

Batteries and chargers have 3 contacts or more. Additional contacts provide a connection to the protection sensor(s) located in the battery. In nickel cells it is a thermal switch. If the battery reaches a temperature of over 4050° then the thermal switch will switch off the charger. The thermal switch must be in the closed position. If it is open all the time, this is a sign of malfunction. You can short-circuit the “T” contact to the “minus” of the battery and charge without overheating protection. But the battery temperature must be monitored and disconnected if the temperature is above 40°C. Lithium ones can have a whole integrated circuit with many protection elements. They monitor not only the temperature of the cells, but also the degree of charge of each.

Failure of an individual cell is detected by the voltage of a charged battery. Even a battery that has no capacity should be able to charge to its rated voltage. If the nominal voltage is met, then all cells have some capacity and deliver a voltage close to the nominal. Conduct training cycles: if the capacity increases, then the battery is recoverable. Continue the practice cycles until the charge and discharge times stop increasing.

When the voltage of a charged battery is a multiple of the voltage of one cell, there is a high probability that the individual battery cells from which it is made will fail. The battery is disassembled and each cell is tested. The defective ones are removed and the defective ones are solder in their place. Two defective batteries can be assembled from one of the remaining serviceable cells.

How to Test


To check the power supply of an electric screwdriver for proper operation, simply take readings of the current and voltage while charging. And you need to repeat the procedure several times to get the most accurate values.

These observations indicate that the battery is completely serviceable and functional. In most cases there will be no need for further analysis.

A healthy battery will also have a steady increase in current strength for approximately one hour after charging begins. If after one hour the value has reached 1 A, it indicates that the device is in good working order.

There is also a method of accelerated testing of the battery, which consists of measuring the voltage at idle (no load). This voltage must reach the necessary value, which is directly related to the operating voltage of the battery cells (banks). If the indicator is lower, then there is a high probability of failure of one or more cells.

A separate type of battery capacity test with a multimeter from an electric screwdriver can be considered testing under load. This method uses auxiliary equipment, which needs to be recharged. Incandescent bulbs are ideal for this. The power of such a lamp must match the capacity of the battery. Otherwise, the test results may not be accurate enough. In most cases, the capacity is half the current delivered by the battery multiplied by the voltage. For standard batteries from electric screwdrivers in the test use a lamp 12 V.

The battery is connected to the load through the multimeter, which then reads. After a few minutes you should measure the voltage. It should be higher than 12.4 В. If such parameter has not been reached, it means that there is obviously some kind of malfunction. In addition it is recommended to pay attention to the brightness of the bulb. It must be sufficiently stable.


The fault may lie not only in the battery but also in the charger itself. That is why you must first check the battery charger for an electric screwdriver with a multimeter.

Turn on the constant current measuring mode on it and use the feeler gauges to connect it to the charger. The amperage value on the meter should be as close as possible to what is indicated on the housing. If this is not the case, it is better to replace the device with a new one.

Battery voltage

After the first step of the test it is clear whether the device is working or not. If testing shows a discrepancy in parameters, it is logical to proceed to repair, which is accompanied by the replacement of defective banks.

It is necessary to open the case of the battery and identify the fault. For this also use a multimeter which is connected to each element separately. The voltage of each bank must be at least 1.2 В. All discrepancies indicate a broken element. Faulty banks must be removed from the common circuit and replaced with new ones.

If such a check will not reveal the breakage, you must again resort to testing under load. And here already fundamental value has the level of resistance, which is directly related to voltage and current. Each element is tested separately and the resistances are also calculated. In the case of a fault, this will obviously be abnormal and will quickly identify the broken element.

electric screwdriver without a battery

Do not rule out a breakdown of the electric screwdriver itself. Using a known good battery or plugging the equipment directly into the mains will help. The second approach is also a great option in case of an urgent need for a tool. Mobility is of course lost, but functionality is quite possible.

An electric screwdriver can be used with an external power supply plugged into a socket. Then you just need to find a rectifier with the necessary parameters. Movements will be limited only by the length of the low voltage cable connected directly to the tool.

It is also possible to build your own prototype of an ordinary mains-powered electric screwdriver. The power supply will then be placed in the battery case and allow you to use the tool quite comfortably. In this case the main issue is to choose the necessary power supply of small dimensions with suitable characteristics. The process can be complicated by the need to find a powerful but compact transformer.

It is advisable to check the battery of an electric screwdriver at regular intervals to prevent various breakdowns at the most inopportune times. Of course, this only applies to the preliminary test, without disassembling the housing. Batteries are fairly short-lived components that need to be periodically replaced. But correct operation with observance of recharging norms will help to keep the devices operable as long as possible.

Testing a Battery with a Multimeter

First, check the parameters several times during charging:

know, electric, screwdriver, battery, charged

Current change mode is uniform. It rises for the first hour after switching on. If index after 1 hour is more than 1 A, the device is in order, there is no need to disassemble it to its component parts. Otherwise you will have to do it by soldering the connections with a soldering iron.

To quickly test the battery with the tester, perform the following actions:

  • by multiplying the number of cells and 1.2 V, you get the value for idling;
  • check the battery of an electric screwdriver using probes on the contacts;
  • compare the data obtained with the idle speed value.

You can compare the obtained result of measurements with the data in the manual. The corresponding value is 1.2 to 1.4 volts for nickel cadmium batteries and 3.6 to 3.8 volts for lithium batteries. Inconsistencies in the results indicate a malfunction in some part of the unit. They are removed from the case to test the battery. Carefully inspect power supplies for rust, signs of electrolyte leakage, and bump marks.

Characteristics of electric screwdriver batteries

Ni Cd (Nickel Cadmium Battery)

appeared and began to be produced before the other types

Capable of remaining in service from approx.50 to 40 degrees Celsius, it is possible to charge at negative temperatures.

Number of recharging cycles from 100. 900 to 2000, depending on technology of the manufacturer

They have the memory effect, so it is recommended to exercise, after the purchase or a long storage, from 3 to 5 cycles, completely discharging and charging the batteries (the manufacturer’s recommendations should be followed), the subsequent observance of the cycles, allows the best possible maintenance of the working parameters.

The self-discharge rate may be as low as 8 to 10%, for more advanced batteries as high as 20.30%, for older versions, of the original capacity.

Can be stored uncharged, in which case they are “immediately” ready for use, after charging.

weight, with relatively similar size to NiMh

Proceed to the replacement of the cells

So, with the types of elements, decided, now disassemble the battery housing, pre-charged to the stop.

Remove all elements from the case and measure voltage of each bank. For the lithium-ion battery, it should be 3.6-3.8 V, for nickel-cadmium. 1.2-1.4 V. Mark on each bank which voltage is less than nominal. Assemble the battery, and work until the power decreases. Disassemble and measure again the voltage of every bank. The voltage drop of unsuitable cells will be significant and they must be replaced.

It is easier to buy new batteries and replace them. Lithium-ion batteries can not be reanimated. Lithium takes about 3 years to decompose.

Batteries were ordered from AlieXpress

, 2 pieces of 3000 mA for 500, but it is important to match the size and capacity of the old batteries, so look at your cells, and then order.

So, to replace the cells, we need a soldering iron, tin, and rosin-based alcohol flux.

When soldering do not mix up plus and minus, do not keep the soldering iron on the banks for a long time. danger of overheating, for joining elements use old plates.

I then did a few charge/discharge cycles, charging the cells to full, then discharging to full with an electric screwdriver. And so several times. it is necessary for alignment of potentials on the banks.

That’s about it. The only thing, if you have nickel-cadmium banks, it’s a good reason to change them for lithium-ion ones

, you only need to choose the right number of cans for the voltage of the “screwdriver”. lithium voltage is three times higher than the nickel-cadmium one. But that is a topic for another article.

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