Drill battery 18650 renewal iasues

Karlbkk

Newly Enlightened
Joined
Dec 6, 2020
Messages
1
Hi all, I'm new here and would like some advice as to where I've gone wrong. I've removed the old 18650 cells from a Wurth Professional cordless drill. However I'm only getting around 7v at the battery-drill terminal instead of 14.4.... I've spot welded new tabs and have all tabs and batteries in the right configuration, exactly the same as the old 18650s that I removed. I did notice that on one side of the circuit board (at the 18650 battery tabs) that I'm getting just over 15v, yet if I probe the other side of the board (at 18650 tabs) I'm getting around 7v only, which is also the voltage I'm seeing at the contact terminals from the battery-drill.
Could the old 18650 batteries that had never been charged and left for 5 years+ have damaged something on the circuit board?
Or are my new 18650 batteries not good enough, even despite I'm seeing 15v on one side of the circuit board..

Thanks for any help you guys can give, my Mrs would like the dining room table to be cleared before the year is out lol
 

lightfooted

Enlightened
Joined
May 6, 2010
Messages
973
Hi all, I'm new here and would like some advice as to where I've gone wrong. I've removed the old 18650 cells from a Wurth Professional cordless drill. However I'm only getting around 7v at the battery-drill terminal instead of 14.4.... I've spot welded new tabs and have all tabs and batteries in the right configuration, exactly the same as the old 18650s that I removed. I did notice that on one side of the circuit board (at the 18650 battery tabs) that I'm getting just over 15v, yet if I probe the other side of the board (at 18650 tabs) I'm getting around 7v only, which is also the voltage I'm seeing at the contact terminals from the battery-drill.
Could the old 18650 batteries that had never been charged and left for 5 years+ have damaged something on the circuit board?
Or are my new 18650 batteries not good enough, even despite I'm seeing 15v on one side of the circuit board..

Thanks for any help you guys can give, my Mrs would like the dining room table to be cleared before the year is out lol

I think it's very likely that something on the board has indeed been compromised, especially if you have simply replaced all of the original cells with new ones. That is assuming quite a bit, but I'm willing to believe that you did your do diligence in making sure that everything was done correctly.

I have found that the cost of cell replacement with even older, more affordable quality cells to not be enough of a savings versus the cost of a new OEM battery pack to bother with. Replacing them with the exact same cells as oem in my Ryobi packs would cost the same as a new pack from Ryobi. Plus I don't have to worry about warranties. Edit: I should say "Plus I GET a warranty"...meaning I don't have to worry about not having one in case the battery melts all over my tools.
 
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Lynx_Arc

Flashaholic
Joined
Oct 1, 2004
Messages
10,777
Location
Tulsa,OK
If you are getting full voltage from the batteries then it is the electronics that are the issue not the batteries. It is likely you either have a bad circuit board or put them back together somehow wrong. I do know a drill I have taps off some (not all) of the batteries for a lower output mode and all of the batteries for high mode.
 

Hooked on Fenix

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Joined
Dec 13, 2007
Messages
2,174
Sounds like your batteries are wired incorrectly. You might have them wired in parallel (in sets of two) instead of series if you're getting half the voltage. Could have also missed a connection between one half of the cells and the other half on one side of the battery pack.
 
Last edited:

Lynx_Arc

Flashaholic
Joined
Oct 1, 2004
Messages
10,777
Location
Tulsa,OK
Sounds like your batteries are wired incorrectly. You might have them wired in parallel (in sets of two) instead of series if you're getting half the voltage. Could have also missed a connection between one half of the cells and the other half on one side of the battery pack.
This sounds plausible getting a wire on the wrong battery to the wrong terminal on the connector could account for the issue if he had a working battery and could double check the voltages/polarities of the terminals maybe that would give a clue as to the problem.
 
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