Replacing batteries in Li-ion cordless drill battery pack.

[alchemysa]

I have a great little 'Ozito' cordless drill that I bought about 4 years ago. It was only a 12v 'cheapie' but it has a 2 speed gearbox so its got a lot of grunt in 'low' plus good speed in 'high'. A nice feature is that the battery packs are small and light and fit inside the handle. Overall its a really handy drill. (The attached pic is from their website).

But the 2 battery packs are just about dead and its not worth buying new ones. However the lithium ion 3.7v batteries that go in the packs are only about $1.50 each (including postage!) on ebay. Each pack holds 3 batteries so I can repower both packs for a grand total of $9.

I googled a bit about this and theres a few dire warnings but it seems to have been done quite easily by a number of people without any great drama. The main danger is a shock or even an explosion if the batteries are accidentally shorted while soldering. I was wondering if anyone here has done this and if they had any problems. I was also wondering if flattening the batteries before assembling would make the job safer.

 

[Soundguy]

you may find soldering to commercial batteries difficult. however.. many 'battery stores' will tackweld solderable tabs to batteries for a couple bucks.

I rebuilt a battery pack in a cordles vac my wife uses. online replacement was 30-45$.. I bought my own, higher capacity bats, and had tabs soldered on for like 16$

 

[alchemysa]

you may find soldering to commercial batteries difficult.

Yes that seems to be the main problem, and sounds like it can be quite difficult without damaging the battery. Will need some experimenting on dead batteries I think, or I'll seek out a battery store and get the tabs welded as you suggest.

The old battteries are 1300mAh. The new ones (when they arrive) are 4000mAh. For the sake of a dollar or two I dunno why they don't use higher capacity batteries in the first place. I guess I might find out.

 

[tcartwri]

Be carefull with the ebay batteries, as most will be counterfeit and of poor capacity.

 

[alchemysa]

Be carefull with the ebay batteries, as most will be counterfeit and of poor capacity.

Quality wise, my expectations are pretty low.

 

[Soundguy]

if you are gonna try to solder to them. use a small tipped high wattage gun to localize heat. lightly scrub the exposed area a hair.. ie. hit it to scuff with sand paper. but not alot. use a good paste flux and wet it and get off it fast. then attach a lead to it, then solder to that.. or.. pay the couple bucks and get them tack welded.

Yes that seems to be the main problem, and sounds like it can be quite difficult without damaging the battery. Will need some experimenting on dead batteries I think, or I'll seek out a battery store and get the tabs welded as you suggest.

The old battteries are 1300mAh. The new ones (when they arrive) are 4000mAh. For the sake of a dollar or two I dunno why they don't use higher capacity batteries in the first place. I guess I might find out.

 

[jinman]

Will need some experimenting on dead batteries I think. . .

That's the best approach. Find out if the basis metal is solderable. We used to use a white ink eraser to clean leads before soldering. The white ink erasers don't contain silicone rubber which will contaminate the metal and cause oxidation when soldering. After using an abrasive, clean the surface with isopropyl (rubbing) alcohol. 99% alcohol is best, but drug store 80% alcohol will generally work. As Soundguy said, the challenge is to get the basis metal to wet (be dissolved) by the solder. It may require a spot weld to get the job done as the metal may not be solderable.