Bringing back a discharged tool battery?

[JOEPRO]

This young and nearly new looking genuine M18 battery was in my other garage on a Milwaukee torch unused for months. I went to use it this morning and it was completely discharged. Milwaukee charger won't recognise it so I'm trying this. Amps are steadily going down which would suggest it's accepting a charge?



The battery status indicator still appears dead though.

 

[MetalMonkey]

Before you do anything you need to take it apart and check the individual cell voltages. If one cell has died you can overcharge the others which can cause them to explode.

 

[Pete.]

I had this happen with a 12v Dewalt. A very short blast on a car charger put enough juice into it so that the deWalt charger could detect the battery connected.

 

[JOEPRO]

Before you do anything you need to take it apart and check the individual cell voltages. If one cell has died you can overcharge the others which can cause them to explode.

I tested it and each cell is showing 3.6v



The battery status indicator is totally dead. Can't see any damage but that may be what is wrong here.

 

[minimutly]

Good thing you're not rellying on it to get around....

 

[JOEPRO]

Good thing you're not rellying on it to get around....

Are you referring to those EV cars that go on fire?

Welcome back BTW

 

[JOEPRO]

I can order a circuit board for £10 ish from ebay.

There is some part of the board on this one that is scalding hot so I think it's faulty.

Some of these tabs are spot welded on type thing. What do I do there and how to you re make these connections?

 

[Sergei Slovenija]

Some of these tabs are spot welded on type thing. What do I do there and how to you re make these connections?

buy nickel tape and a spot welder for battery cells. China will help.

 

[voipio]

If the scalding hot part is only hot during charging, then it's either faulty, or there's a charge balancing circuit dumping power, to protect one cell/group of parallel connected cells.

 

[Guineafowl]

Some of these tabs are spot welded on type thing. What do I do there and how to you re make these connections?

You can wheedle them apart with something sharp and flat. Then reflatten with pliers, scrub clean, flux, tin and solder. High powered gun-type iron is best. If the tab is on a battery, use a damp rag to suck the heat back out once tinned, so the heat doesn’t travel into the battery.

 

[julianf]

I can order a circuit board for £10 ish from ebay.

There is some part of the board on this one that is scalding hot so I think it's faulty.

Some of these tabs are spot welded on type thing. What do I do there and how to you re make these connections?

If you're replacing the PCB then you can do it with a normal soldering iron. I can't remember the details but possibly you have to solder one of the bars, but it's well away from the cells so it's entirely possible. I have done it on an M18. It wasn't hard.

I have all the parts for another battery. I bought one of the Chinese spot welders. It burnt up instantly.

Watched various YouTube on running them off large batteries, and convinced myself to buy another. It burnt up instantly.

Twice bitten thrice shy...

 

[julianf]

Ps the symptoms on mine was just the same - all cells read fine, battery wouldn't work.

Cheap pcb off Ali express, and it was fine, and still is. I recon it must have been over a year ago that I changed it.

 

[optima21]

I solder Li-ion 18650 cells with a 50W temperature controlled iron and a 3/16" bit. I clean the end of the cell, then tin the end of the cell (after applying flux), then solder a tinned wire to that(. it should take less than a couple of seconds to solder and the cells shouldnt get warm

 

[Migmac]

If you're replacing the PCB then you can do it with a normal soldering iron. I can't remember the details but possibly you have to solder one of the bars, but it's well away from the cells so it's entirely possible. I have done it on an M18. It wasn't hard.

I have all the parts for another battery. I bought one of the Chinese spot welders. It burnt up instantly.

Watched various YouTube on running them off large batteries, and convinced myself to buy another. It burnt up instantly.

Twice bitten thrice shy...

I’ve replaced one too and it’s been fine since I did it

 

[JOEPRO]

I ordered a circuit board for it.

Then by chance I pressed the botton on it again this evening and low and behold the first red light came on flashing. It put no lights on at all earlier today.

I put it into an older, slower M18 charger I have and it appears to be charging now

 

[JOEPRO]

Yep it charged up fully no issues. 4 red lights and charger went green.

I have about 20 batteries (milwakee, dremil and parkside) I will gather them all tomorrow and make sure they all hold a charge. I think some parkside 12v ones are dead but new!

 

[ukracer]

You can wheedle them apart with something sharp and flat. Then reflatten with pliers, scrub clean, flux, tin and solder. High powered gun-type iron is best. If the tab is on a battery, use a damp rag to suck the heat back out once tinned, so the heat doesn’t travel into the battery.

Those gun types are crap for cells. The only one we found that worked was a chisel printed 12 volt version.

 

[Ross365]

I've soldered on to an 18650 a few times and it's been OK.

The advice seems to be that if a that trying to recover a Li-ion cell which has been discharged to <2V, they say don't try and I haven't! Have you seen videos of those things burning ?

 

[JOEPRO]

I've soldered on to an 18650 a few times and it's been OK.

The advice seems to be that if a that trying to recover a Li-ion cell which has been discharged to <2V, they say don't try and I haven't! Have you seen videos of those things burning ?

This M18 battery was around 0.2v this morning! Then I put it on a power supply set at 18 volts for 10 minutes or so which was enough to bring the voltage back up. After this is when I opened the battery and all cells were at 3.6v approx.

Maybe I just got lucky this time.

 

[m_c]

There is a risk to recovering over-discharged cells, but it's usually worth the gamble.
However I'm pretty sure I wouldn't have put 4A through them.
I'd usually aim around 0.1-0.2C (C being Capacity in Ah I.e. if it's 2.0Ah cell, aim for 0.2-0.4A), until the voltage recovers to a more reasonable level (somewhere over 3V for Li-ion), and keep a very close eye on them for any signs of heating up.