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I have seen a lot more power tool battery repair videos cropping up, particularly Dewalt. Not bosch, but I imagine most of the top brands are using cells from the same few factories.
So the question is, how long has Dewalt been selling liion batteries? A quick google search reveals it was in 2011-ish. So the failure rate has started going up at about 10 years.
Only battery I have that won't charge is a Chinese clone, one of two. I shouldn't have let it discharge so much.
Not sure it's worth repairing.
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(11-08-2021, 10:16 AM)EricU Wrote: Only battery I have that won't charge is a Chinese clone, one of two. I shouldn't have let it discharge so much.
Not sure it's worth repairing.
I'm pretty sure LiIon cells can be damaged if they're too deeply discharged. I know the Bosch batteries have circuitry to disable the battery before they're damaged, I imagine other reputable manufacturers have similar. The drills won't really slow down as the battery discharges. It goes from running full speed to off. Put the battery on the charger and a few minutes later it's as good as new.
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Dewalt has a very simple circuit in their batteries that doesn't do much, I'm pretty sure you can over-discharge them. The only protection is the charger won't charge a battery pack that's too unbalanced. If you go looking on youtube, there are videos about brand new dewalt batteries that won't charge. I'm not sure I understand how that happens, but there are ways to balance them.
It seems to me that a circuit to keep a battery from over-discharging would be somewhat unlikely. But I imagine someone has looked at that between the various brands.
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(11-13-2021, 07:41 AM)EricU Wrote: Dewalt has a very simple circuit in their batteries that doesn't do much, I'm pretty sure you can over-discharge them. The only protection is the charger won't charge a battery pack that's too unbalanced. If you go looking on youtube, there are videos about brand new dewalt batteries that won't charge. I'm not sure I understand how that happens, but there are ways to balance them.
It seems to me that a circuit to keep a battery from over-discharging would be somewhat unlikely. But I imagine someone has looked at that between the various brands.
Here is a paper about overdischarge in lithium-ion batteries. It is pretty advanced and I don't claim to understand 98% of it.
https://www.nature.com/articles/srep30248
Quote:Abstract
Lithium-ion batteries connected in series are prone to be overdischarged. Overdischarge results in various side effects, such as capacity degradation and internal short circuit (ISCr). However, most of previous research on the overdischarge of a cell was terminated when the cell voltage dropped to 0 V, leaving the further impacts of overdischarge unclear. This paper investigates the entire overdischarge process of large-format lithium-ion batteries by discharging the cell to −100% state of charge (SOC). A significant voltage platform is observed at approximately −12% SOC and ISCr is detected after the cell is overdischarged when passing the platform. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) results indicate that the overdischarge-induced ISCr is caused by Cu deposition on electrodes, suggesting possible Cu collector dissolution at the voltage platform near −12% SOC. A prognostic/mechanistic model considering ISCr is used to evaluate the resistance of ISCr (RISCr), the value of which decreases sharply at the beginning of ISCr formation. Inducing the ISCr by overdischarge is effective and well controlled without any mechanical deformation or the use of a foreign substance.
