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Why the cordless drill motor not run? Answered

Hi all,
I have a problem with the motor of the cordless drill.
I converted my cordless drill from Ni-Cd battery to Li-ion battery 12v6 using the protected PCB as this image: http://www.ultest.com/shop/image/cache/catalog/Power-Modules/HX-3S-A01-1-500x500.jpg.
After connecting the 3 cells Li-ion battery to PCB, I measured the voltage at P+ and P- is 12v.
So the connection between the battery and PCB is correct!
Try to connect P+ and P- (from PCB) to the positive and negative terminals of the motor, then the PCB cut-off voltage at the output pin.
The reason is the 2 terminals of the motor is connected (using the Digital Multimeter to check).

How to resolve this problem with the motor working properly?
Sy Do



7 months ago

A comparitor IC can be set up to open a switch (relay) when the battery voltage reaches the proper stop level..

I will try your way but I don't know what kind of relay is suitable for my case?

If you want I will draw it up 4 U ?

I'm very happy if you do it for me.

Start with a DPDT 12v relay place a 0.1uF disc capacitor C2 across the motor to quiet brush noise. Whenever you push the button the relay will latch closed and stay that way until the relay current is interrupted by the 2N2222 NPN transistor being driven by U1 the 30V LM311 comparitor 8pin DIP IC..

The LM311 will drive the transistor as long as pin2 is more positive then pin3..

The 3.3 volt zener diode Z1 and resistor R2 holds pin3 at 3.3 volts until the battery falls below say 5 volts..

The 20K pot V1 lets you adjust the voltage to pin2 which is going to be proportional to the battery voltage...

You can adjust the pot to a setting that makes pin2 fall below 3.3v pin3 at 10v or 9v or less battery and shut off the motor relay... The .01uF C1 capacitor prevents pot noise from tripping the ckt when you turn the pot

The zener is 11 cents at.


Please click the pic to see the whole circuit..

Motor V Stop.bmp

Assuming that 1. Your getting electricity to positive AND negative terminals of the motor.

2. The voltage is correct

3. The battery pack can supply enough current for the motor to run

Then there isn't any reason why it wont work.

SO one of these 3 things isn't hapening.


1. correct

2. voltage is 12v => correct (I have tried to connect the motor to the 12v power source of the computer PSU and the motor working properly)

3. my battery has the max ampere is 10A => correct

I guess the cause is BMS board. It cut off the power when 2 poles + and - are in contact with each other, but I don't have ideas to fix it.

Just wire the battery direct to the motor with a switch, forget the speed control.

In your way the motor will work properly, but I'm afraid my battery will be broken because it is not protected over discharge.

That depends on how you use it.

IF the protection cct is not allowing your battery pack to provide the necessary current I suggest you have a battery miss match.

You need a battery pack that CAN provide the current. Other wise my suggestion is your only choice.

I would consider using a new battery pack :D.