# Milwaukee battery jump start



## Debo22 (Feb 15, 2015)

My flashlight and 18v battery was left on inside a furnace about 8 months to a year ago. I finally got it back and it was flashing bad cell when I tried to charge it. I googled how to reset it and this video came up. I tried it using a 5 amp fuse and it blew instantly. In the video he says to use a 20 amp fuse. I wanted to run it by you guys before I use a bigger fuse because I don’t want to smoke a good battery trying to save this one. What do you guys think?


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## Debo22 (Feb 15, 2015)

...


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## Plumbus (Aug 4, 2008)

If you like trying to fix tools, go for it.
Otherwise, how much is your time worth to you?


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## Debo22 (Feb 15, 2015)

Plumbus said:


> If you like trying to fix tools, go for it.
> Otherwise, how much is your time worth to you?


I kind of like tinkering with stuff, I just don’t want to kill a good $100+ battery trying to save another


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## Logtec (Jun 3, 2018)

Debo22 said:


> Plumbus said:
> 
> 
> > If you like trying to fix tools, go for it.
> ...


I’d just cut my loss and move on, it’s not worth blowing the next battery.
You were out One battery for a year, You must have moved in with out it..
(All this said like your women went to prison...)


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## Plumbus (Aug 4, 2008)

Good point on both counts. 

Feeling lucky, pilgrim?


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## Debo22 (Feb 15, 2015)

Skoro will know


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## skoronesa (Oct 27, 2015)

Debo22 said:


> Skoro will know



DO NOT USE A 5amp or higher fuse. I suggest 1 or 2 amps.



Those cells should be able to handle 4-5amps output each BUT they don't handle charging as fast well, especially when one or more cells has a much different voltage than the others.



You've got two and a half options. The first is hook it up in parallel like you did with a fuse but use a piece of steel wire as a makeshift current limiting resistor. It will get very hot. You could use wire cut from an old oven rack. This is the less desirable option.


Option two is to individually charge each cell by using some probes and sticking them in the smaller slots. Ideally you would use a dedicated lithium cell charger like the nextar vc4 which I have two of, theyre only 20$ and work great.


Option two and a half is to open the case to gain access to connect and charge each pair of cells individually. *This is the best option *as you avoid any charging circuitry in the battery controller that could get in the way.




I can go into more detail and even provide pictures if need be. I just got home from a 5-1/2hr call and the wife needs help cleaning so it won't be immediate.



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## breplum (Mar 21, 2009)

I see no issue with just getting a 20amp fuse and trying the exact method.
The fuse will protect your "good" battery, in case something is shorted on the old battery. 

The found flashlight reminds me of walking into a customer's basement a few years after a major remodel. I see my Jumbo folding aluminum 3' stepstool, with my name emblazoned on both sides. Sheesh.


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## skoronesa (Oct 27, 2015)

breplum said:


> I see no issue with just getting a 20amp fuse and trying the exact method.
> The fuse will protect your "good" battery, in case something is shorted on the old battery.
> 
> The found flashlight reminds me of walking into a customer's basement a few years after a major remodel. I see my Jumbo folding aluminum 3' stepstool, with my name emblazoned on both sides. Sheesh.





20 amps is a lot of current for those cells. What they're trying to do is force a charge into the cells before the protection can kick in. This is assinine when you can charge each cell individually the proper way and actually restore it.


Jolting it with 20+ amps(fuses aren't instantaneous) might not "break" it but it certainly will phuck those cells up good.




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## Debo22 (Feb 15, 2015)

skoronesa said:


> 20 amps is a lot of current for those cells. What they're trying to do is force a charge into the cells before the protection can kick in. This is assinine when you can charge each cell individually the proper way and actually restore it.
> 
> 
> Jolting it with 20+ amps(fuses aren't instantaneous) might not "break" it but it certainly will phuck those cells up good.
> ...


Since my brother was the one who left it there I told him we’re using his Makita battery to do the jump. That way if it fails it’s his battery that’s going to get smoked. 

I was thinking of using a piece of bailing wire to act as the resistor instead of using copper wire. What do you think?


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## skoronesa (Oct 27, 2015)

Debo22 said:


> Since my brother was the one who left it there I told him we’re using his Makita battery to do the jump. That way if it fails it’s his battery that’s going to get smoked.
> 
> I was thinking of using a piece of bailing wire to act as the resistor instead of using copper wire. What do you think?



Definitely don't use copper wire, it will pass more current. I would start with a pretty long piece of that bailing wire, like 3 feet. The shorter it is the more current it will pass and being so thin it may melt and splatter. If it gets red hot disconnect it.


You ever light steel wool on fire? Fun fun! When I was in high school I had a piece of steel wool and a AAA battery in my pocket. Ended up burning a hole through my pocket and burning my leg lolz


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