How to discharge the ni cd battery of an electric screwdriver
How to “charge-discharge” an electric screwdriver battery? How often? How to erase the “memory effect”?
There is a concept of a fully discharged battery for the purpose of further operations and of a battery discharged to zero that requires resuscitation. How many volts the battery should be discharged depends on the model and the number of cells in the battery. Cells are connected in series, the voltage at the output terminals is summed. This is why the discharge limit is different for acid, alkaline, and lithium batteries.
Whether a new battery needs to be fully discharged? Yes, if it is a Ni-ion or Ni-MH battery type. Such batteries have a memory effect. You must fully discharge them 3 to 5 times before use, then charge them again. Any charging of this type of battery must then be carried out after it has been fully discharged. Only leave the battery fully discharged for storage. How much can you discharge a nickel battery?? The training cell is brought up to 0.9.1,0 В. Knowing the number of cells, you can calculate for yourself how many volts to discharge the battery.
People often ask if a new lithium-ion battery has to be discharged. There is no memory effect in this type of cell. Operates steadily at moderate levels of charge. That’s why you can charge the battery at any convenient moment with a special charger. Can a lithium-ion battery be fully discharged?? It is possible, but after a discharge below 3.2 volts special charging methods are required, at 2.0 volts the cell cannot be restored. A typical deep discharge is 2.5 volts per cell.
How many volts can a lead-acid battery can be discharged? With a cell output voltage decrease of 1.70V, the total voltage of the 6 cell battery will be 10.3V. A fully discharged battery will have a minimal reserve of survivability. Do I have to discharge an acid battery completely?? Maintenance-free calcium-ion car battery can be destroyed even after one deep discharge. All acid batteries after a deep discharge inevitably lose some capacity due to plate sulfation.
Different types of batteries require a varied approach to maintenance. Therefore, whether it is necessary to fully discharge the battery, new or in the process of calibration and testing, is written in the instruction manual of the device.
Troubleshooting the Battery
Suspect a faulty electric screwdriver battery or have it repaired should not be done immediately, but first try to replace it with a second one from the set, before charging it properly. If the electric screwdriver does not spin properly, it could be caused by a breakage in its mechanics (motor or gearbox). In case of doubt, it is necessary to replace the power pack, if possible. If everything points to the battery, then you can begin to diagnose and repair it.
The first thing to do is to find out what type of battery it is. It is written on its case and the possibility of recovery depends on it. The nominal voltage should also be stated. It usually lies in the range of 14 19 V. Then, without disassembling the case of the battery pack, test it. Two methods can be used for this:
The multimeter can be used in two modes: measuring voltage and measuring current. If there are two gauges, that’s even better, you won’t need to make unnecessary switches.
A measurement scheme is shown below: One multimeter switches to voltage measurement mode (voltmeter), the other switches to current measurement mode (ammeter). If there is only one device, then instead of an ammeter you will have to use just a wire. The wires from the battery to the voltmeter can be thin, and the wires from the power source to the battery can be thicker, but do not get too carried away, after all, for the whole circuit will be suitable wire 0.5 mm cross section.kv.
If the battery voltage is normal, but the charging current is low, much less than one amp, then for Ni-Cd battery it may mean a fault of one of the battery cells. Electric screwdriver battery recovery is off the table here, repair is needed. For Li-ion, this means that either it is normal, or also a failure of one of the cells.
Suppose the Ni-Cd battery has a nominal voltage of 18 volts. Then it is easy to find out how many cells are inside without opening the case. Knowing the rated voltage of Ni-Cd 1.2 V, divide: 18/1.2 = 15. So, there are 15 cells in the case. If the voltmeter shows an idle voltage of 16.8 V, it could also mean that one of the cells is short-circuited, or just a normal battery is discharged. Such a battery, when discharged, would give 15 volts. If the charged one shows 16,8 V or so, it means that one of the cells is short-circuited. There is no way to repair it, you have to replace it.
If the battery when charging passes current of more than one amp, and the voltage gradually increases, increasing by 0.1 V every 5-10 minutes, and at the end of the charge the voltage is slightly higher than the nominal, then the battery is fine, restoration is not required.
This method is similar to the previous one and is probably easier. No need to disassemble charger or use laboratory power supply. Only the load will be needed:
Test Pattern: To do this test, first put the battery on a charge and charge in the normal manner. Then a nominal load is applied. It is easy to find out the current, just divide absorbed power by nominal voltage. For example, if your electric screwdriver has a power consumption of 50W (typical case) at 18V, the current should be 50/18 = 2.77A. To get to this current, or close to it, you can dial in parallel car turn signal bulbs.
If the battery gives the nominal current for several minutes, the voltmeter shows a voltage slightly below the nominal, and the lights do not dim, then the battery is serviceable. It may however happen that for Ni-Cd soon the current starts to weaken. This is a manifestation of the “memory”. In such a case you need to reconstruct. Lithium ion batteries have no memory effect, although in theory it exists, in practice it is believed that it simply does not exist.
Element by element check
This method requires disassembly of the battery case. It is used when the battery or a cell stops delivering a good current and recovery attempts are unsuccessful. A single bad link is enough here because they are connected in series. But to find such a cell, you must check the internal resistance of each of them.
Of course you start with a general inspection of all the jars, check for cracks, leaks, etc.д. A faulty cell will immediately give itself away.
Check for the current output using Ohm’s law for a complete circuit (aka Kirchhoff’s first law). To do this, you need to take a resistor of 10 ohms, rated at 25 W, and an ammeter. The cell to be tested is short-circuited by a resistance included in series with the ammeter.
For example let the Ni-Cd battery with a voltage of 1.2 V have a current of 100 mA. Let’s write it down and measure again but not the current but the voltage on the cell. First we measure the no-load voltage, without connecting the resistor, and then we connect the resistor and see how much the voltage has dropped. Suppose the first time it was 1.2 V, and after connecting a resistor it was 1.05 V. Then the internal resistance of this cell: This is not too low, if all the cells are like this, then the battery can only supply half the power to the electric screwdriver. The lower the internal resistance, the better the cell is, but with a prerequisite: it must deliver the rated voltage, or close to it. If the voltage is too low or too close to zero, then the cell is shorted, it is useless and can not be restored. If the internal resistance is greater than 3 Ohm, then we can try to repair it (see Fig.1). see below) or replace.
How to disassemble the battery
If a faulty battery is detected, you need to proceed to the detection of faulty banks. all cells rarely fail at the same time, and to create problems it’s enough to one or more lagging banks. Therefore, the repair of batteries for an electric screwdriver should begin with the disassembly of the battery and removal of the cells. Do not disconnect them yet.
The order of disassembly depends on the design of the case. Somewhere you have to unfasten the latches, and somewhere you have to remove the self-tapping screws or screws. After removing the cover pull out the battery cells.
Battery jars removed from the case.
Before you disassemble the battery, you must visually inspect each cell. If among them there are bloated, mechanically damaged, with traces of electrolyte leakage or corrosion, such banks without a second thought should be marked as faulty. There is no need to remove them.
Voltage of other elements should be measured. If it does not meet the rating (or even below the lower limit), the jar should be tried to charge. It is not necessary to disconnect the battery in this case, either.
Charge a single cell.
For this you will need a voltage source with a regulated output. If charging fails, the battery is discarded. Cells, which were successfully brought up to par value, must be tested separately for capacity and current efficiency according to the methodology mentioned above. If the bank does not hold the charge or does not give enough current, it is rejected.
Important! Pull up the charge of the lithium-ion battery with the balancer board turned off. It can interpret a deep discharge as a fault and block the cell.
Capacity and current output of a single cell.
Correct discharge: how to do it?
How to properly discharge a battery. a question that may seem strange. It is worth noting right away that you can not do it by turning on the tool at full power. over, if you continuously and idly “twist” connected to the electric screwdriver, it can lead to the fact that it simply broke. And full discharge of cadmium batteries in this way still can not be achieved due to the fact that the remaining charge they hold long and stable.
There is a much more reliable and gentle method in which the battery is discharged quickly and without harming the electric screwdriver. For this you need to use an ordinary light bulb.
How to discharge the battery of an electric screwdriver
The electric screwdriver battery uses cylindrical cells of nickel-cadmium, lithium-ion batteries. They are different in maintenance. New nickel cadmium cell battery needs to be run down. To discharge the battery, you have to use a 12-volt bulb as a load. The battery is discharged when the incandescent light goes out.
Lithium-ion batteries do not need to be pumped. It may be necessary to calibrate, for the correct operation of the controller. In such a case, you must use a smart device with a discharge function.
How to properly charge a new battery?
For nickel-cadmium and nickel-metal hydride batteries, initial charging cycles are important to allow them to use their full capacity. Batteries of the first type should be completely discharged, and then charged three times to reach the maximum capacity. They are then only fully charged, the end of this process will be indicated by indicators or a warming of the case. The second type batteries require 4-5 cycles of full discharge and recharging. Next, charge them as needed without waiting for complete discharge. Nevertheless, the discharge-discharge cycles are regularly repeated 4-5 times to restore the capacity.
Lithium-ion batteries have no memory effect, so there are no recommendations on how to properly charge a new li-ion battery for an electric screwdriver.
How to Recharge an Electric Screwdriver Battery
When working with a cordless electric screwdriver sooner or later the battery begins to run down quickly, or it stops charging at all. To work in such conditions is almost impossible, so you have either to buy a new battery, or restore it with your own hands. On how to restore the battery of an electric screwdriver, and we will talk in this article.
How to correctly and reliably charge the battery of an electric screwdriver?
Everyone should know how to properly handle the tool so that it will last for the longest possible period. Every tool has its weaknesses, and with an electric screwdriver it is the battery. It is important to know in advance how to correctly charge the battery of an electric screwdriver, so that you don’t have to wonder why the device failed so quickly.
Schematic diagram of the charger to charge the battery of an electric screwdriver.
The nuances of charging different types of batteries
Charging drives of different materials is distinguished by the following aspects:
- rated voltage, current and recovery time;
- The need for a charge-discharge cycle;
- storage characteristics;
- the ability to recharge when not fully discharged.
Charging parameters are indicated in the instruction manual of the tool and the battery label. Nominal voltage is a multiple of the voltage of 1 power cell and depends on the number of banks.
A full discharge and charge cycle is required to restore the rated capacity when the “memory effect” occurs. It is recommended to repeat the procedure several times.