Power tool battery revival

[leenowell]

Hi all,

I have a few 18v Graco (same as DeWalt lithium ion) batteries for my paint sprayer which seem to charge well but then die very quickly. Once charged they show just over 20v on the multi meter. I have been doing some searching and come across people saying

1. Zap them with 36v - although this seems to be if they are not charging at all
2. Slowly drain them until tool doesn't work any more. Leave them and drain again. Repeat until completely dead and then charge.

Does anyone know if this works or is there a better option? For option 2, my sprayer only has one setting so will this have the same effect or do I need to find another way to discharge them eg somehow find a 18v ish bulb ?

Thanks in advance for your help

Lee.

[Bill Wright]

You could discharge them using two 12V bulbs in series, or indeed anything intended for 18V or more. You could use an electric fire element. But it won't work.

Bill

[Tricky Dicky]

It is my understanding that Litium Ion batteries should not be fully discharged and usually contain circuits to prevent this happening. Some of your advice applies more to NiCads.

Richard

[Brian Reay]

Those techniques are recommended by some for NiCd (and sometimes NiMH) cells/batteries. I'd not try them on Li cells- especially the zapping one.

Generally, if an Li cell is dead, it is done for.

[Brian Gaff]

Well those batteries sound to me like they are knackered. One has to be careful as often each cell has protection circuitry to stop them blowing up or catching fire! Brian

[Brian Gaff]

Yes I thought that and to some extent the older nickel metal hydride types as well.

Lithium/ion ar a whole other animal indeed depending on their construction several different animals. Some are like normal batteries some are like a kind of thin set of electrodes squished up together... I know a technical term! One tends to have individual cell failure as with the older types and of course because its being reverse charged by the others running the load it is well knackered fast and turns into a resistor. The others can get very hot and burst into flames hence the protection!

Brian

[Theo]

Neither.

Charge them up, then take them apart and measure the voltages across each cell as the battery is discharged (the car bulb suggestion is a good one). You'll probably find one or more of the cells drops rapidly, which causes the whole pack to cut out. A healthy Li-ion cell should be 4.2V when fully charged, dropping to about 2.5V when empty (and the protection circuit should cut in).

You can try replacing the dead 18650 cells (requires a tab welder or cells with pre-welded tabs - or using a pack for donor cells). But it might be easier to buy a new battery, which will last longer.

Theo

[The Natural Philosopher]

Once lithyum are dead,they are dead.

No zombie jooz avaialable.