Lack of power batteries overheating

Question

Dewalt dc390 cordless circular saw

Mark Watts @markwatts26519

Rep: 1

1

2

Publicado: 13 de feb. de 2016

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Lack of power batteries overheating

Hi all

Hopefully someone can help , I got a dewalt dc390 cordless circular saw , and seems to run slow speed and has lack of strength when cutting , battery also seems to get very hot and takes ages to cool down .

Now seems like a low power battery but I have 4 batteries 2 of which are new and same happens with each . I can just about cut a small piece of wood by using all batteries but each battery last max 30 sec - 1 min .

Obviously there is some fault. With the circular saw . Does anyone have any idea what might be the cause .

Spare parts are readly available and I can change myself but need to know how to test what part so I can order correct part ?

Motor , armature, brushes ( but no sparks that I can see) etc

Any suggestions much appriciated

Thanks Mark

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oldturkey03 @oldturkey03 Rep: 782.2mil 1.1mil 893 2.3mil · Answer 1 · 2016-02-13T14:47:20-07:00

oldturkey03 @oldturkey03

Rep: 782.2mil

1.1mil

893

2.3mil

Publicado: 13 de feb. de 2016

Opciones

Mark Watts, "slow speed and has lack of strength " sounds like you are having issues with the motor. If it has shorted starter windings it can cause the issues you described. This could cause pulling to high amperage from your battery and cause those to become depleted and hot. Of course, you also want to check all the bearings since this could cause the motor to draw higher amperage as well.

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Hi Oldturkey

Thanks for that had a feeling was the motor but when get time to disassemble I will check the bearings also .

If it is the motor does that call for a new motor or do you think could be rewound ?

Thanks Mark

13 de feb. de 2016 - de Mark Watts

That would depend on where you are at what your resources are. There are some decent places that do rewinding but could be costly. You can check with a multimeter to see what amperage the motor draws. That should give you a better idea what you are looking at. Check on here https://www.youtube.com/watch?v=9Zt3P9bv... different device same idea

13 de feb. de 2016 - de oldturkey03

Hi Oldturkey03

Thanks for info and link , I think if done correctly I am getting approx

1st pull of trigger 7-7.3A then settles on 5.56A

2nd pull 7-7.1A then settles on 5.45A

Wires on multimeter very hot

3rd pull 7-7.6A then settles on 5.5A

4th pull similar again

This is on a newish battery with fresh charge

I also opened up the Circular saw , don't think could get rewound easy as sealed unit ?

Bearing seems ok but have nothing to compare it to .

But when remove Magnet ring from Armature it spins freely and top bearing seems fine and spins ok with no desert able play . With magnet ring attached then harder to spin .

So do these results seem like it's the motor ? As I have no idea what the Amps should be for this cordless circular saw ?

Thanks Mark

13 de feb. de 2016 - de Mark Watts

Little heavy on the amperage but there is not a lot of information out about the motor. I'll try and check some more sources.

14 de feb. de 2016 - de oldturkey03

Sounds good thanks

14 de feb. de 2016 - de Mark Watts

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