Monthly Archives: October 2013

How to calculate the number of cells in a Li-ion cordless power tool battery

In my last article, we know how to calculate cells in Li-ion laptop battery, and what a 18650 battery cell is. And, let learn How to calculate the number of cells in a Li-ion cordless power tool battery.

It is known that the Li-ion Cordless tool battery is also made by 18650 battery cell. So, it is very easy to calculate the number of cells in a Li-ion power tools.

For example, the Makita BL1830 Battery, it is a 18 V, 3000mAh battery. How many cells in it? Let’s calculate it.

To make the voltage to 18 V, it needs 5 series of 3.6 V cell, and to make capacity to 3000mAh, it needs 2 parallels of 1500mAh cell. So, the total of a 3000mAh Makita BL1830 battery is 5*2 = 10 cells.

But, some people may say, why not use a 3.6 V 3000mAh battery cell to build it? The reason is, power tools is heavy duty machine, it need much more power than the nomal laptop battery, so the density of the chemistry material is much more than laptop battery cell. It is hard to do it.

For Li-ion cordless tool batteries or notebook batteries, normally speaking, the higher capacity (mAh), the larger in size, and heavier in weight. Of course, more capacity means longer run time. A 1500mAh 18 V battery will run longer than the 3000mAh 18 V battery, but may not the running time.

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How to Calculate the Number of Cells in a Li-Ion Laptop Battery

You may find that most of laptop manufacturers will state how many cells in their Li-ion laptop battery, such as Dell, Sony, ACER and so on. Further more, many laptop battery reseller also say the number of cells of their Lithium-ion Laptop battery.

But, do you know to calculator the number of cells?

First of all, let’s know the inside of a Li-ion Laptop battery, it is made with outside plastic case or aluminum case, circuit boards, 18650 battery Cells. These are the main three parts of a Li-ion notebook battery.

So, what are 18650 battery cells?

It is called by its size, the diameter of it is 18.6 mm and the length is 65.2 mm, so the name is combined with the first two numbers of the diameter and length. This cell type is used in many laptop batteries, the Tesla Roadster, Tesla Model S, and LED flashlights.

Because most of the Li-ion notebook batteries are made with 18650 battery cells, and the capacity of it is 1800 mAh to 3400 mAh, this depends one what cells the battery use.

The voltage is 3.7 V, but, some battery cell manufacturer may say 3.6 V, in fact, 3.7 V and 3.6 V rechargeable is the same thing. Those are the mean/average voltages under load and it has to do with fully-charged-open-circuit-voltage. 10 years ago Li-ions were only charged up to 4.1 V and the mean/average voltage under load was 3.6 V. A few years later the manufacturers changed this to 4.2 V to increase the capacity of the batteries. Obviously this else made the mean voltage under load increase.

Even today, though it still makes sense to only charge your batteries (18650 for example) only up to 4.1 V as this drastically increases the life expectancy (number of cycles) of the batteries while only reducing the capacity by ~10%. Many hobby chargers allow doing this.

Now, we know what a Li-ion laptop battery is made of, and let’s calculate the number of cells.

As we know, series in physics makes current the same, but voltage will plug one by one, parallel makes the voltage the same, but Current will plug one by one.

For example, a 10.8 V 4400 mAh Lithium-ion laptop battery, in order to have the 10.8 V, it must take 3 battery cells, and in order to have 4400 mAh, it must have 2 cells. So, this needs 6 cells, and this is the number of the Li-Ion Laptop battery.

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5 different shapes of Bosch cordless power tools Battery

When using a Bosch cordless power tools, you need a battery. If you have many cordless drills, hammer, planer, circular saw, impact wrench and so on, the rage of the voltage is from 3.6V to 36V, so you have a large selection on Bosch tools. But, do you know how many battery shape of all Bosch cordless tools battery? Let me show you.

There are 5 shape of battery on batteries for Bosch cordless tools.

First, Bosch straight-shape battery packs.

In this range, you can find it in 3.6V, 10.8V tools.

For example,

3.6V straight-shape battery: Bosch 2 607 336 242 Battery
Bosch 2 607 336 242 Battery
10.8V straight-shape battery, Bosch 2 607 336 014 Battery

Second, Bosch Flat-shape battery packs

Here are the examples:

7.2V flat-shape battery: Bosch 2 607 335 033 battery
Bosch 2 607 335 033 battery
9.6V flat-shape battery: Bosch 2 607 335 037 battery

12V flat-shape battery: Bosch 2 607 335 055 battery

14V flat-shape battery: Bosch 2 607 335 210 battery
Bosch 2 607 335 210 battery
Third, Bosch bulb-shape battery pack, it just looks like a bulb.

7.2V bulb -shape battery: Bosch 2 607 300 001 battery
Bosch 2 607 300 001 battery
9.6V bulb -shape battery: Bosch 2 607 300 002 battery
Bosch 2 607 300 002 battery
12V bulb -shape battery: Bosch 2 607 335 021 battery
Bosch 2 607 335 021 battery
Fourthly, Bosch pod style battery pack

9.6V pod style battery: Bosch 2 607 335 540 battery
12V pod style battery: Bosch 2 607 335 262 battery
Bosch 2 607 335 262 battery
14.4V pod style battery: Bosch 2 607 335 694 battery
Bosch 2 607 335 694 battery
18V pod style battery: Bosch 2 607 335 266 battery
Bosch 2 607 335 266 battery
24V pod style battery: Bosch 2 607 335 510 battery
Bosch 2 607 335 510 battery
The last one is the Bosch slide-in battery packs, this type of battery is always Li-ion batteries.

14.4V slide-in battery: Bosch 2 607 336 224 battery
Bosch 2 607 336 224 battery
18V slide-in battery: Bosch 2 607 336 236 battery
Bosch 2 607 336 236 battery
24V slide-in battery: Bosch 2 607 335 216 battery
2 607 335 216 battery
36V slide-in battery: Bosch 2 607 336 002 battery
Bosch 2 607 336 002 battery

Now, you know the shape of the Bosch power tools battery, the next time when buying the battery, I suggest you to check the shape of your old battery, otherwise, you may buy the wrong one.

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10 tips on making the Ni-CD and Ni-MH rechargeable Cordless power tools run longer

If you want your cordless power tools to be durable use, you must know how to maintenance it. But, for tools used with Ni-CD or Ni-MH batteries, the main point is how to protect the battery and charger. in order to better protect the battery and charger, here are some particular attentions:
1. When in summer, the temperatures are high, long working hours make the battery to high temperatures, and even produce burst phenomenon, so, attention should be adapted to control the battery temperature.
2. After a battery is fully charged, the charger will be hot, so it is better to charger another battery after 10-15 minutes.
3. Because the Ni-CD and Ni-MH battery has the “Memory effect”, long-term improper charging and discharging will made the battery life shortened.
4. Batteries are chemical substances is prohibited hit the water, otherwise there is risk of a problem but will not be able to repair, to replace the battery, the old battery can only be scrapped。
5. Unplug the power of charger when there is no battery.
6. Charging the best in the room, the temperature is below 38 degrees is best.
7. Thunderstorms often occur in summer, when lightning and voltage instability, please do not charge the battery, because this will may the charger easy to burn.
8. Pay attention to the working environment, to avoid metal is sucked inside the motor magnetic motor, this will cause the motor stuck phenomenon.
9. Recharged the battery for every two months if not used, otherwise it may appear the phenomenon of cell necrosis.
10. Old batteries should appoint good collection and treatment, so as not to pollute the environment.

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