Need help getting high current DC motors to work

Thread Starter

SesamBread

Joined May 24, 2019
8
I have an electric car seat laying around at home which has a couple brushed DC motors inside.
The motors are rated at 12V and I am trying to get them moving but for some reason neither my old PC power supply (rated at 15A) nor my li-ion battery pack (4S4P 16.6V, rated at 10000mAh and 10C) seem to be powerful enough to make the motors move the chair.
Shouldn't the battery already be beefy enough?
I was going to buy an external power supply to connect to the seat but it confuses me that the battery doesn't seem to be powerful enough.

It would be really great if someone could clear things up for me!

Thank you very much in advance! :)
 

BR-549

Joined Sep 22, 2013
4,938
You need the paperwork or specs of the motors. That will tell you what the motor is and what it needs. And it shows the wiring connections.
 

MaxHeadRoom

Joined Jul 18, 2013
20,425
Did you try them on an automotive battery? If they still don't move, there is something else at play that has been overlooked.
Can you test them off of the seat?
Some modern automobile motors are PWM, vents, windows etc.
Max,
 

Thread Starter

SesamBread

Joined May 24, 2019
8
Thank you for your quick responses! :)
I was able to find the motor no. A2108201242 but there is no datasheet or anything online.
I can make the motor work without any torque when disconnected with just 2 cables as it seems to be a usual DC brushless motor. (2 other cables seem to be for the hall effect sensor)
Am I maybe just missing something? The battery should be able to provide up to 100 A since it's rated at 10C, am I right?
Unfortunately i don't have the equipment to measure the current when I connect it to the motor.

Edit: Unfortunately I don't have an automotive battery at hand either.
 

MaxHeadRoom

Joined Jul 18, 2013
20,425
The typical BLDC typically have 3 stator connections and the motor has a controller, some automotive applications are no exception.
Max.
 

MaxHeadRoom

Joined Jul 18, 2013
20,425
The typical auto seat motor has a G.B. attached, generally worm and pinion.
Are you sure the other two wires are hall sensors for a DC brushed motor?
Max.
 

Thread Starter

SesamBread

Joined May 24, 2019
8
Well I had to open one of them to get some rust out and there are only to thicker cables which are connected to the coil and to thinner cables connected to some small pcb on top. I assumed that it's the hall effect sensor since I couldn't take analyze the pcb better due to it's location.
What exactly is a "G.B."?
Thank you very much for helping me out! :)
 

MaxHeadRoom

Joined Jul 18, 2013
20,425
Doesn't look like your typical DC brushed motor, if it can be detected what each pair of conductors feed, it may shed some light on it, is it possible to try and spin the motor shaft, if P.M. DC then the armature pair should generate if spun, if you don't have a meter, then shorting the two wires should make it difficult to spin,.
Max.
 

MisterBill2

Joined Jan 23, 2018
5,771
Power seat motors may draw quite a bit of current, possibly 25 amps, since they are only run occasionally, and never for very long at a time. They are almost always brush type because they will probably never run 100 hours in their lifetime.
So what are you wanting to do with powered seat motors? They are not suitable for many other applications.
 

Thread Starter

SesamBread

Joined May 24, 2019
8
Then I don't understand why the battery doesn't provide enough current! It should be powerful enough, shouldn't it? It has 10000 mAh and a 10C rating at 14-16v.
I just wanted to use the seat as a regulatable chair at home!:)
I was also thinking about using one of the motors maybe as a door opener for my front door. Would you suggest that use? Or would it's lifetime expectancy be reached too fast?
 

MisterBill2

Joined Jan 23, 2018
5,771
Then I don't understand why the battery doesn't provide enough current! It should be powerful enough, shouldn't it? It has 10000 mAh and a 10C rating at 14-16v.
I just wanted to use the seat as a regulatable chair at home!:)
I was also thinking about using one of the motors maybe as a door opener for my front door. Would you suggest that use? Or would it's lifetime expectancy be reached too fast?
Battery internal resistance increases as the battery ages and this means that the voltage drop under load increases as well. NEW batteries can provide a lot of current for a short time, but as they age that drops. Also, if the seat motors are not new they may have problems as well. Have you been able to run the motors from a car battery? If they are used motors there may be some failure that has happened.
 

djsfantasi

Joined Apr 11, 2010
6,338
What vehicle did this seat come from and what is/was the fuse rating? Different vehicle/motors require different fuses. If the vehicle that this came from uses fuses greater than 10 amps, you may not be able to run the motor with your battery.

Many people have asked you to try with an automotive battery. You claim not to have one. Do you drive a car? Disconnect one cable (to protect the car) and use an automotive fuse rated for 10 amps inline.

It seems that a bad ground or short to the seat or motor frame often causes abnormal current draw and fuse blowing up to a 20 amp fuse.

Trying to drive a bad motor will only lead to frustration. I recommend starting at step 1 and make sure the motor works.
 

MisterBill2

Joined Jan 23, 2018
5,771
What vehicle did this seat come from and what is/was the fuse rating? Different vehicle/motors require different fuses. If the vehicle that this came from uses fuses greater than 10 amps, you may not be able to run the motor with your battery.

Many people have asked you to try with an automotive battery. You claim not to have one. Do you drive a car? Disconnect one cable (to protect the car) and use an automotive fuse rated for 10 amps inline.

It seems that a bad ground or short to the seat or motor frame often causes abnormal current draw and fuse blowing up to a 20 amp fuse.

Trying to drive a bad motor will only lead to frustration. I recommend starting at step 1 and make sure the motor works.
In some parts of the world there are not as many cars and not everybody owns one. And it may be that the TS does not have friends who own cars. But in any case, the TS needs to monitor the battery voltage while trying to run the motor, since that may provide some really useful insight. AND, sometimes frustration leads to innovation, and that can be quite valuable.
 

Thread Starter

SesamBread

Joined May 24, 2019
8
That is not a battery capable of running that motor. Trying to run a 25Amp motor with 10amp battery is why it won't run under a load.
Shouldn't a battery rated at 10000 mAh (which to my knowledge is its capacity and not its power output) and at 10C discharge output at max. 100A and not 10A. Please tell me where my calculations are off.:)

I don't know why it seems so unbelievable that I don't have a car. Is this an American thing? As a student in Germany you just don't need a car to get around and I currently don't have access to any of my friends' cars.
I guess I will just have to buy a power supply rated at 30A or 40A.

Battery internal resistance increases as the battery ages and this means that the voltage drop under load increases as well. NEW batteries can provide a lot of current for a short time, but as they age that drops. Also, if the seat motors are not new they may have problems as well. Have you been able to run the motors from a car battery? If they are used motors there may be some failure that has happened.
The Li-po battery pack I used isn't the newest and I hardly used it but this might explain it.

Thank you all for your replies.
 
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