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The Heat Is On (Jumpstarting a Battery Pack)


fm2176

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A while back one of my DeWalt 20v Max 2Ah batteries decided to give up the ghost.  It was always a "special" pack, as the battery charge indicator didn't work and there was some clear condensation on the indicator bars, though it gave me about three good years of service.  Over the weekend, I finally got around to jumpstarting the pack, resulting in failure and a situation that almost got too hot to handle...

 

I started by using a car battery and short 4-5 second jolts.  After about ten repetitions I took it inside and the charger didn't read it.  So, after consulting a couple of how-to pages, I used a 5Ah battery and connected the two for about five minutes.  The 5Ah dropped a bar after a few minutes, but immediately showed a full charge when I disconnected them.  Meanwhile, the 2Ah battery was putting out just a slight bit of heat at the terminals after the five minutes elapsed.  The charger still wouldn't read it so I let it sit, but the battery steadily heated up for the next half-hour or so.  Needless to say, I placed it a safe distance away and left it alone for a few hours.

 

I'll try to get some pics this week, but the pack eventually cooled off with no obvious deformation.  However, the plastic housing appears to have some heat damage, with surface cracks and an area that is either a bit of dirt or melted plastic.  Unfortunately, I didn't have anything to disassemble the pack the following day, so I'll do that this week as well.

 

Something is obviously very wrong with my battery.  It could be a short or some other issue, but let this serve as notice that jumpstarting batteries not only isn't guaranteed to work, but can be potentially dangerous.  Years ago, I witnessed a car battery blow up next to me (fortunately, the hood was down), and I don't want anything to do with a lithium cell rupturing, burning, or exploding.

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After always respecting your knowledge and your posts, what would lead to your concluding that this is a good idea?

 

An online search did not reveal any web pages showing how this would / could freshen a battery.

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On 5/26/2021 at 10:41 AM, wingless said:

After always respecting your knowledge and your posts, what would lead to your concluding that this is a good idea?

 

An online search did not reveal any web pages showing how this would / could freshen a battery.

 

There are a number of sites and videos, including this article from Popular Mechanics, which is the one I referenced.  I used to specialize in electrical systems, having been trained by both GM and Crown Forklift, so I know that in principle this should work.  Especially in the case of 20v Max to 20v Max pack, the weakened battery should receive enough power to revive the cells and allow the charger to read the battery pack.

 

I disassembled the battery this morning and found that it has obvious signs of water damage.  There isn't really any corrosion, but the metal battery connectors are rusted and a few of the cells themselves are swollen.

 

Will I attempt this again?  Perhaps, with another out of warranty battery pack, but with a quick examination of the internals first.  Does it work?  From what I hear, yes, not only from online sources but also from my brother who revived two M18 5.0 batteries.

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