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DeWalt battery fully charged but not working


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I have a DeWalt DCB107 charger and x2 dewalt 18V lithium ion 1.5AH batteries. I was using my dewalt DSC390 circular saw and drained both batteries, or so I thought, I was only sawing for maybe 2 minutes each battery, I was sawing a fresh 2x4 at an angle so it was under pressure. When I put one battery on the charger the yellow over heat light came on so I tried the other and the yellow light also came on. So I left both sit outside for 10 minutes then tried x1 on the charger, the red light came on and stayed, this indicated full charge, I tried the other battery and it did the same. I tried both batteries in the saw and my drill and neither worked. I tested both batteries with a volt meter and they read 14v to 15v. I read online that the batteries can shut down if they overheat and to reset them place them in the charger for 8hrs, I did this with one battery overnight and it’s still the same.

It seems that the batteries are charged but have shut down!!

Is this possible?

How are they reset?

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14v to 15v is far from charged.

 

Make sure your DMM battery is good and check the voltage of the battery again measuring from the B+ to B- terminals.

 

Thermistor check #1 Measure the voltage from B- to TH, you should get the same voltage as the B+ to B- measurement.

Thermistor check #2 Measure the  Resistance (Ohms) from B+ to TH, it should be around 12k

 

If that is all good, then test the individual cells to see if one has gone bad. Measure..

 

B- to C1 = ?.??v

C1 to C2 = ?.??v

C2 to C3 = ?.??v

C3 to C4 = ?.??v

C4 to B+ = ?.??v

 

All of those measurements should be the same, or within a hundredth of a volt of each other.

 

 

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Your voltage is too low and the charger won't charge them, time to jumpstart them.  Take a fully charged working battery and 2 short wires, stuff one end of each wire in the the + and - of the working battery then connect one wire to the matching terminal of the dead battery, and tap the 2nd wire to the other terminal for 1/2 a second or so.  This should bring the voltage up enough to get your charger to work.

 

Also, those 1.5 ah batteries shouldn't be used on any saw, obviously they get you no runtime, the draw is too much for those little batteries.  I only use double stacked batteries on like the 4ah and larger one mine, you'll get noticably more power.

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  • 3 months later...
On 12/24/2019 at 4:20 AM, Micheal said:

I have a DeWalt DCB107 charger and x2 dewalt 18V lithium ion 1.5AH batteries. I was using my dewalt DSC390 circular saw and drained both batteries, or so I thought, I was only sawing for maybe 2 minutes each battery, I was sawing a fresh 2x4 at an angle so it was under pressure. When I put one battery on the charger the yellow over heat light came on so I tried the other and the yellow light also came on. So I left both sit outside for 10 minutes then tried x1 on the charger, the red light came on and stayed, this indicated full charge, I tried the other battery and it did the same. I tried both batteries in the saw and my drill and neither worked. I tested both batteries with a volt meter and they read 14v to 15v. I read online that the batteries can shut down if they overheat and to reset them place them in the charger for 8hrs, I did this with one battery overnight and it’s still the same.

It seems that the batteries are charged but have shut down!!

Is this possible?

How are they reset?

 

On 12/24/2019 at 4:20 AM, Micheal said:

I have a DeWalt DCB107 charger and x2 dewalt 18V lithium ion 1.5AH batteries. I was using my dewalt DSC390 circular saw and drained both batteries, or so I thought, I was only sawing for maybe 2 minutes each battery, I was sawing a fresh 2x4 at an angle so it was under pressure. When I put one battery on the charger the yellow over heat light came on so I tried the other and the yellow light also came on. So I left both sit outside for 10 minutes then tried x1 on the charger, the red light came on and stayed, this indicated full charge, I tried the other battery and it did the same. I tried both batteries in the saw and my drill and neither worked. I tested both batteries with a volt meter and they read 14v to 15v. I read online that the batteries can shut down if they overheat and to reset them place them in the charger for 8hrs, I did this with one battery overnight and it’s still the same.

It seems that the batteries are charged but have shut down!!

Is this possible?

How are they reset?

Did you ever find out the answer? My saw 

keeps shutting down too after 3/4 of the 1st 2x4 being cut. I can get it to spin but as soon as it hits the wood it fizzles out to nothing. Recharging now to see if that helps. 

image.jpg

FFE5B8DD-BE03-48FA-BD32-D50612F7A752.jpeg

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On 12/30/2019 at 8:29 AM, Cr8ondt said:

Your voltage is too low and the charger won't charge them, time to jumpstart them.  Take a fully charged working battery and 2 short wires, stuff one end of each wire in the the + and - of the working battery then connect one wire to the matching terminal of the dead battery, and tap the 2nd wire to the other terminal for 1/2 a second or so.  This should bring the voltage up enough to get your charger to work.

 

Also, those 1.5 ah batteries shouldn't be used on any saw, obviously they get you no runtime, the draw is too much for those little batteries.  I only use double stacked batteries on like the 4ah and larger one mine, you'll get noticably more power.

 

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Thank you for the heads up that I need my double stacking battery pack for the saw! Will go try that! And can you please post a set of photos showing the battery wiring stuff you just commented about. My with wiring with our photo instructions may not end up in a good place! 🙂

image.jpeg

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