Accumulators and batteries What is the difference between a lithium battery and a nickel-cadmium battery. Calculation of t component schemes of alteration. Operating conditions of the lithium battery. Features of alteration of batteries and chargers from different manufacturers.
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Converting a Makita screwdriver to a lithium battery
There is a Makita screwdriver with a 1.3 A / h battery and a voltage of 9.6 V. To change the power source to a lithium-ion one, you will need 3 18650 components. Alteration will give the old tool new opportunities: power, as the operating voltage rises to 10.8 V.
The design will require the use of a BMS, a control controller that maintains the lithium cell operating mode within operating limits. With this breaker, each cell will be charged evenly without exceeding 4.2V, lower voltage 2.7V. A built-in balancer is used here.
The parameters of the controller should accompany the operation of the instrument when the operating current rises to 10-20 A. The Sony VTC4 30 A board, designed for a capacity of 2100 A / h, can ensure operation without shutdown. Of the 20 amperes, the Sanyo UR18650NSX accepting energies of 2600A / h is suitable. The board is needed for 3 elements, which is marked in the 3S classification. In this case, the board must have 2 contacts, plus and minus. If the conclusions are designated with the letters P-, P, C-, they are intended for later models of screwdrivers.
A step-by-step instruction on how to convert a Makita screwdriver to lithium batteries looks like this.
- You can disassemble the battery with glue if you tap the junction with a soft-headed hammer while weighing. The direction of impact is downward, into the joint on the lower part of the body.
- Take only contact plates from the old assembly, carefully disconnecting them from the battery. Leave the sensor and breaker.
- Solder 3 elements in series using TAGS flux and insulated jumpers. The wire cross section must be greater than 0.75 mm2.
- Assemble the circuit with the controller, and connect the power supply to the contact connectors with 1.5 square wires.
- Check the functionality of the circuit and reassemble the case by placing it on the glue again.
In a screwdriver with an old DC9710 charger, after charging the 18650 lithium battery, the red LED on the panel will turn off. The built-in controller monitors the charge level.
The Makita DC1414 T charger is used to charge 7.2-14.4 V power sources. While charging, the red light is on. But when charging a lithium battery, its voltage does not fit into the standards of salt products, and after 12 V, the charger will flash red and green. But the required charging is already there. The screwdriver is ready for use.
Conversion of a screwdriver to lithium batteries 18650
Every craftsman is faced with the problem of reduced tool performance, or complete failure due to the battery. Manufacturers use nickel-cadmium batteries in 12, 14, 18 volt screwdrivers. The sequential assembly of several elements creates the required voltage. Replacing nickel-cadmium batteries with lithium batteries extends battery life, making the design easier. Mandatory BMS board installation adds reliability. Therefore, the conversion of a screwdriver to lithium batteries, mainly to the 18650 form factor, is justified.
Translation of the Hitachi screwdriver into lithium
At present, there are a great many different batteries, protection boards, balancing boards, chargers, etc. It was necessary to select the right one and glue it together.
So, it was decided to supply high-current Li-Ion batteries. The consumption current of different screwdrivers can reach 30A and the batteries must be able to deliver such a current. Cheap fingers costing 80r apiece cannot do this.
It was also decided to abandon the balancing BMS board, since all batteries were selected and were the same. By and large, at the beginning of operation it is not important.
The following pair of batteries in a collapsible case was subject to alteration:
It was necessary to collect a battery of 4 batteries. The protection board was used on the basis of 4 batteries and 20A current. I do not specifically give the link, because very soon it will be inoperative. Search for a position by keywords
4S 14.8V / 16.8V 20A peak li-ion BMS PCM battery protection board bms pcm
The set turned out like this:
We assemble the battery with soldering of all contacts with an ordinary soldering iron. Please note: the connection of the assembled battery to the protection board MUST be carried out strictly in the following sequence: B-, B1, B2, B3, B:
It turns out such a set for assembly:
Now we are preparing the contact pads:
You need to add a terminal for the charger to the case and you will get this final assembly:
Pay attention to how you fix the contact pad on the top of the battery. The self-tapping screw must be screwed in exactly in this place.
Here it is necessary to clarify. There are also protection boards with one contact group per charge and discharge. Here it is used with separate connectors, so the charging terminal is taken out separately. I recommend placing it in the specified place.
Now with regard to charging such a battery. You can remake a native charger (this is not difficult and will be discussed in another article, perhaps), but I decided to sell my own charger, and use an extra power supply from a laptop with a voltage of 18 volts. At its output, a controller for the end of charging was made of the following type (built into the power supply case):
After charging is complete, the LED will turn off reliably. The charge current in this case was 1.5A and at the end of the charge before disconnection was about 1A. The full charging time of the battery was about 1.5 hours.
Budget: each set for one unit was 1000r and its service life will be unlike a regular nickel-cadmium battery.
Minus one: it is not advisable to use it in cold weather.
It is also necessary to take into account that in a more powerful screwdriver it is necessary to use protection boards with an operating current of 30A, otherwise, under difficult operating conditions, the protection board will go into protection and de-energize the screwdriver. In this screwdriver with this protection board, such a problem has never been noted.
Let’s start with the benefits:
- The energy density of lithium-ion cells is much higher than that of nickel-cadmium, which are used by default in screwdrivers. That is, the battery on lithium cans will have less weight than on cadmium with the same capacity and output voltage;
- Lithium battery cells are charged significantly faster than Ni-Cd. It will take about an hour to charge them safely;
- Lithium Ion batteries have no memory effect. This means that they do not need to be fully discharged before charging..
Now about the disadvantages and difficulties of lithium batteries.
What do you need to estimate before starting work?
Also, more lithium cells will give more capacity. This means more operating time of the screwdriver.
Lithium battery cells 18650
The nominal voltage of lithium cells is 3.6-3.7 volts, and the capacity in most cases is 2000-3000 mAh. If the battery case allows, you can take not 4, but 8 cells. Connect them two by two in 4 parallel assemblies, and then connect them in series. As a result, you will be able to increase the battery capacity. But not every case will be able to pack 8 cans of 18650.
And the last preparatory stage is choosing a controller. According to its characteristics, it must correspond to the rated voltage and discharge current. That is, if you decide to assemble a 14.4 volt battery, then choose a controller with this voltage. The working discharge current is usually chosen to be two times less than the maximum permissible current.
Charge-Discharge Controller Board
All pros and cons of converting a screwdriver battery to lithium cells
First you should think about whether I need this alteration? After all, it will be a frank self-propeller and in some cases can lead to failure of both the battery and the screwdriver itself. Therefore, let’s consider all the pros and cons of this procedure. It is possible that after that some of you will decide to abandon the conversion of the Ni─Cd battery for a screwdriver to lithium cells.